EP2163126A2 - Method for the sound processing of a stereophonic signal inside a motor vehicle and motor vehicle implementing said method - Google Patents

Method for the sound processing of a stereophonic signal inside a motor vehicle and motor vehicle implementing said method

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Publication number
EP2163126A2
EP2163126A2 EP08806093A EP08806093A EP2163126A2 EP 2163126 A2 EP2163126 A2 EP 2163126A2 EP 08806093 A EP08806093 A EP 08806093A EP 08806093 A EP08806093 A EP 08806093A EP 2163126 A2 EP2163126 A2 EP 2163126A2
Authority
EP
European Patent Office
Prior art keywords
signal
frequency
phase
signals
electrical
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP08806093A
Other languages
German (de)
French (fr)
Other versions
EP2163126B1 (en
Inventor
Frédéric AMADU
Yann Lecoeur
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Arkamys SA
Original Assignee
Arkamys SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Arkamys SA filed Critical Arkamys SA
Publication of EP2163126A2 publication Critical patent/EP2163126A2/en
Application granted granted Critical
Publication of EP2163126B1 publication Critical patent/EP2163126B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R5/00—Stereophonic arrangements
    • H04R5/02—Spatial or constructional arrangements of loudspeakers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S3/00—Systems employing more than two channels, e.g. quadraphonic
    • H04S3/002—Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S7/00—Indicating arrangements; Control arrangements, e.g. balance control
    • H04S7/30—Control circuits for electronic adaptation of the sound field
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R2499/00—Aspects covered by H04R or H04S not otherwise provided for in their subgroups
    • H04R2499/10—General applications
    • H04R2499/13—Acoustic transducers and sound field adaptation in vehicles
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S2400/00—Details of stereophonic systems covered by H04S but not provided for in its groups
    • H04S2400/05—Generation or adaptation of centre channel in multi-channel audio systems

Definitions

  • the invention relates to a sound processing method for a stereophonic signal broadcast in a motor vehicle and a motor vehicle implementing this method.
  • the invention particularly aims to increase the comfort of listening to a soundtrack in a car.
  • This soundtrack may contain for example a telephone conversation and / or music.
  • the invention finds particular advantageous application in sound processing methods implemented with audio systems with two input channels and four, five or six output channels.
  • the stereo signal comprising a left sound signal (1 st lane) and a signal of the right (2nd channel) generated by a stereophonic source (such as radio) is broadcast on channels 4 .
  • a fifth channel can also be generated and broadcast by a transducer located in the center of the dashboard.
  • a transducer is a system that transforms an electrical sound signal into an acoustic sound signal.
  • a transducer connected to a given channel comprises two loudspeakers which diffuse respectively the high frequency part and the low frequency part of the electrical signal of its conveyed by the way.
  • a first speaker called “tweeter” broadcasts the high frequency part of the signal of the channel
  • a second speaker called “woofer” broadcasts the low frequency part of the signal of the channel.
  • some transducers can be positioned so that the sound seems to come from the bottom of the vehicle, which does not provide a very pleasant listening impression to the passengers.
  • the invention solves this problem by positioning the sound stage on the plane of the ears of each passenger, in front of each passenger and / or in the middle of the edge range of the vehicle.
  • it is sought to minimize the phase opposition effects between the left and right signals received at the head location of at least one of the passengers.
  • the stereophonic sound source is centered in the middle of the dashboard for the “driver” listening position.
  • delays are introduced in the frequency bands of each speaker, so that all the speakers seem to be at the distance from the one which is farthest from the driver.
  • the resultant phase of the signals of the front channels and the phase of the signals of the rear tracks perceived by the listeners are equalized, so that the sound source seems to be centered in front of each passenger.
  • delays in the front channel signals are introduced to temporally align the tweeter / woofer pairs.
  • the invention therefore relates to a sound processing method of a stereophonic signal inside a motor vehicle, the stereophonic signal being composed of an electrical signal of its left and an electrical signal of its right, in which ,
  • the phase of these electrical sound signals is equalized so as to minimize the phase opposition effects in frequency bands of these left and right signals received substantially at the head of one of the passengers, and the electrical signal of its left equalized in phase is diffused and the electrical signal of its equalized right in phase respectively with the aid of a left front transducer positioned in the left front part of the vehicle and a right front transducer positioned in the right front part of the vehicle.
  • filters are applied to the electrical signal of his left and / or the electrical signal of his right, so that the phase difference curve between the electrical signals of his left and right received at the location of the passenger's head bypasses the points where the electrical signals of his left and right received are in phase opposition.
  • all-pass filters are applied to the left or right signal, these all-pass filters each having a cut-off frequency substantially equal to a center frequency of the band of frequency for which the electrical signals of his left and right received are in phase opposition.
  • all-pass filter pairs are applied, one of the filters of the pair being applied to the electrical signal of its left and the other filter of the pair being applied. to the electrical signal of its right, the filters of a pair having cut-off frequencies which surround a middle frequency of the frequency band for which the electric signals of its left and right received are in opposition of phase.
  • the all-pass filters are of Infinite Impulse Response (IIR) type.
  • the filters are of the RIF type, in Response
  • these filters each having a phase response each having the appearance of an inverted gate having a value of -180 degrees on a frequency band where the received signals are in phase opposition. According to one implementation, it is considered that the electrical signals of its receipt are in phase opposition when the phase difference between these signals is 180 degrees plus or minus 20 degrees modulo 360 degrees.
  • phase opposition effects are minimized for a frequency band between 20 Hz and 2 kHz.
  • the frequency spectrum of the left and right electrical signals is equalized so as to compensate the acoustics at the front of the vehicle, using a spectral correction module.
  • frequency bands of each electrical sound signal are filtered, and delays are introduced into these frequency bands. The delays are chosen so as to temporally align the speakers of the left front transducer as well as the speakers of the right front transducer diffusing these frequency bands.
  • the low frequency portion and the high frequency portion of each electrical sound signal are filtered, the delays being chosen so as to temporally align the loudspeakers respectively diffusing the low and high frequency portions of the electrical signal of its sound. left, the delays being chosen so as to temporally align the speakers respectively diffusing the low and high frequency parts of the electrical signal of his right.
  • the left and right delays applied to the high frequency loudspeakers are identical, and the left and right delays applied to the low frequency loudspeakers are identical, because of the geometry of the vehicle. However alternatively they could be different.
  • the frequency bands of the loudspeakers correspond to the frequency bands of the filtered signals that they broadcast.
  • the frequency bands of the electrical signal of its left are combined into an electrical signal of its reconstituted left, this electrical signal of its left reconstituted being diffused by the left front transducer. While the frequency bands of the electric signal of his right are combined in an electrical signal of his right reconstituted, this electric signal of his right reconstituted being diffused by the right front transducer.
  • the frequency bands of the electrical sound signals are adjusted in volume by gain cells.
  • an electrical signal of its central is generated from the spectral components in phase of electrical signals of its left and right originals of a stereo source, this electrical signal of its central being broadcast, after introduction of a delay, and adjustment in level and volume, by a transducer positioned in the center of the dashboard.
  • the electrical signal of its left and the electrical signal of its right are obtained by subtraction of the spectral components of the electrical signal from its central respectively to those of the electrical signal of its original left and those of the electrical signal of its original right.
  • electrical signals are generated from its left and right back, from substantially out of phase components. electrical signals of his left and right, these signals being diffused, after introduction of a delay and adjustment in level and volume, respectively by a left rear transducer and a right rear transducer.
  • the invention furthermore relates to a sound processing method of a stereophonic signal inside a motor vehicle, the stereophonic signal being composed of an electrical signal of its left and of an electrical signal of its right, in which frequency bands of each electrical sound signal are filtered, and delays are introduced into these frequency bands.
  • the delays are chosen so that the transducers diffusing these frequency bands lie virtually on a circle, this circle having as a center the location where the conductor is located and having a radius whose distance is that which separates the conductor from the transducer. further away from the driver.
  • the low frequency part and the high frequency part of each electrical sound signal are filtered, the transducers each comprising a low frequency loudspeaker and a high frequency loudspeaker, the delays being then chosen so as to time align the loudspeakers diffusing respectively the low and high frequency parts of the electrical signal of his left.
  • the delays are chosen so as to temporally align the loudspeakers respectively diffusing the low and high frequency parts of the electrical signal of its right.
  • the left and right delays applied to the high frequency speakers are identical, and the left and right delays applied to the low frequency speakers are identical.
  • the invention furthermore relates to a motor vehicle comprising a sound source generating a stereo signal inside a car, this stereo signal being composed of an electrical signal of its left and an electrical signal of its right, these electrical signals of left and right being processed by the method according to the invention so as to be respectively distributed by a front left transducer comprising only a speaker and a right front transducer comprising only a speaker.
  • the front left and right speakers are wide-band speakers.
  • FIG. 1 a functional schematic representation of an audio system implementing the "driver" mode according to the invention
  • FIG. 2 a functional schematic representation of an audio system implementing the "ail passengers" mode according to the invention
  • FIG. 3 a functional schematic representation of an audio system according to the invention with 2 input channels and 6 output channels;
  • FIGS. 4-5 schematic representations of the virtual location where the center of the sound stage is located respectively during the implementation of the method according to the invention in "driver” mode and the implementation of the method according to the invention in "passenger passengers” mode.
  • FIG. 6 a graphical representation of the phase difference between the front left and right signals received at the head of one of the passengers before and after phase correction;
  • FIG. 7 a graphical representation of a phase response of a "pass-all" filter used to minimize the phase opposition between the acoustic signals received at the location of the head of one of the passengers ;
  • FIGS. 8 graphical representations of the phase responses of two "all-pass" filters and of their combination, as well as the phase response of a Finite Impulse Response filter. Identical elements retain the same reference from one figure to another.
  • FIG. 1 shows a functional schematic representation of an audio system implementing the "driver" mode making it possible to position the center of the sound scene for a listening position instead of the driver of the vehicle.
  • the audio system according to the invention has two input channels 2 and 3 and four output channels 20, 25, 34 "and 35" respectively diffused by the transducers 21, 26, 39 and 41. More specifically, a sound source 1, such as a CD player, generates a stereo signal composed of an electrical signal 2 of its left and an electric signal 3 of its right (2 input channels).
  • a sound source 1 such as a CD player
  • This module 4.1 equalizes the spectrum of signals 2 and 3.
  • the module 4.1 comprises a filter that smooths the perceived spectral response of the electrical signals of its 2 and 3, so that all the frequencies emitted at a given power tend to be perceived at the same amplitude level by the driver.
  • a known signal is diffused using the transducers 21, 26 before left and right, and the signal at the driver's head using a microphone.
  • a transfer function called “vehicle transfer function” is deduced therefrom, and from the inverse transfer function of the "vehicle transfer function", the filter coefficients are parameterized so that the defects of the spectrum of the recorded signal are compensated for. way to find the spectrum of the initial signal.
  • This module 4.1 thus creates a spectral shape that compensates for the acoustics of the vehicle, so that the audible signals diffused at the front of the vehicle by the transducers 21, 26 and perceived by the driver (after the sound signals have been passed inside of the vehicle) have a spectrum as close as possible to that of the original sound signal.
  • An electric signal of left equalized and an electric signal of its equalized right is obtained at the output of module 4.1.
  • These signals 5 and 6 are applied at the input of a block 7 allowing a spatial correction of the signals 5 and 6.
  • these signals 5 and 6 are respectively applied at the input of a high pass type filter 9 and a low pass type filter 10.
  • a high pass type filter 9 and a low pass type filter 10 At the output of the filter 9, an electric signal 5a of its left high frequency and an electric signal 6a of its high frequency right are obtained.
  • an electric signal 5b of its left low frequency and an electric signal 6b of its low frequency right are obtained.
  • the cutoff frequencies of the filters 9 and 10 correspond to the cut-off frequencies of the loudspeakers used for the diffusion of the filtered signals. In one implementation, these cutoff frequencies are substantially identical. In other words, the frequency bands of the filtered signals correspond to the frequency bands of the loudspeakers broadcasting these filtered signals.
  • two loudspeakers 22.1, 22.2 and 27.1, 27.2 are connected to each channel in order to broadcast respectively the high frequency bands and the low frequency bands.
  • the electrical signals of its left and right are each respectively filtered by 3 filters, each corresponding to one of the frequency bands of these 3 speakers (high, medium or low).
  • the signals 5a, 5b and 6a, 6b are then each applied to the input of a delay cell 13.1-13.4.
  • the adjustment of the delays t1-t4 introduced is made according to the positioning of the speakers in the car, in particular according to the distance to which they are from the driver.
  • delays t1-t4 are introduced on the signals 5a, 5b and 6a, 6b, so that all the front loudspeakers seem to be at the distance RHPmax of the transducer 41 furthest from the driver's head 62 (FIG. see Figure 4).
  • the frequency band intended to be broadcast by the farthest speaker is not delayed, whereas the frequency bands broadcast by the loudspeakers closer to the driver's head are delayed by one. delay such that the sound broadcast by these closer speakers seems to be perceived at the same time at the driver's head than that to which the signal of the farthest speaker is perceived. In other words, the frequency bands are delayed so that the sounds broadcast by all the speakers are perceived at the same time at the location of the driver's head.
  • the conductor 62 is then in the center of a circle C of radius RHPmax on which the images S1-S4 of the loudspeakers 22.1, 22.2, 27.1, 27.2 are located, as represented in FIG. 4.
  • the distance between each loudspeaker and the driver is first measured and a delay is introduced according to this measurement in the frequency bands broadcast by the speakers other than the one furthest away, so that all the speakers appear to be at the RHPmax distance of the farthest speaker.
  • the delayed signals 5a ', 6a', 5b 'and 6b' observable at the output of the cells 13.1-13.4 are applied at the input of cells 15.1-15.4 gain.
  • These cells 15.1-15.4 allow an adjustment of the volume of the high and low frequency sound signals.
  • the delayed signals are multiplied by coefficients K1-K4, for example between 0 and 1.
  • the electric signal 5a of its left high-frequency processed signal observable at the output of the cell 15.1, and the electric signal 5b "of its left low frequency processed observable at the output of the cell 15.3 are applied at the input of an adder 17.1.
  • This signal 20 corresponds to the left front channel (first output channel) diffused by a transducer 21 having two speakers 22.1 and 22.2 positioned in the left front part of the vehicle.
  • the first speaker 22.1 (the "tweeter”) broadcasts the high frequency portion of the signal 20, while the second speaker 22.2 (“the woofer”) broadcasts the low frequency portion of the signal 20.
  • the electrical signal 6a of its processed high frequency right observed at the output of the cell 15.2, and the electric signal 6b of its observed low frequency right observed at the output of the cell 15.4 are applied at the input of an adder. 17.2.
  • This signal 25 corresponds to the right front channel (second output channel) diffused by a transducer 26 comprising two speakers 27.1 and 27.2 positioned in the right front part of the vehicle.
  • the first speaker 27.1 (the "tweeter") broadcasts the high frequency portion of the signal 25, while the second speaker 27.2 (“the woofer”) broadcasts the low frequency portion of the signal 25.
  • the high frequency and low frequency portions of the signals 20 and 25 diffused by the loudspeakers 22.1, 22.2 and 27.1, 27.2 correspond, as we have seen, to the frequency bands filtered by the high frequency and low frequency filters 9 and 10.
  • the high-frequency signals 5a "and 6a" of electrical sound are diffused respectively by a transducer 29 and 30 comprising only a loudspeaker 31, 32 having a high frequency band.
  • the transducers 21 and 26 directly broadcast the signals 5b "and 6b". We then have one loudspeaker per channel and no longer two loudspeakers per channel. In this case, the summers 17.1 and 17.2 are suppressed.
  • the signals 2 and 3 are applied at the input of a second spectral correction module 4.2.
  • this module 4.2 compensates the vehicle acoustics for the channels 34 ", 35" rear of the vehicle.
  • At the output of module 4.2 are observed electrical signals 34, 35 of its left and right equalized.
  • these signals 34 and 35 are respectively applied at the input of delay cells 13.5 and 13.6.
  • These cells 13.5, 13.6 each introduce a delay t5 and t6 in the signals 34 and 35, so that all the transducers seem to be virtually at the distance RHPmax of the loudspeaker farthest from the conductor, as shown in FIG.
  • signals 34 'and 35' observable at the output of the delay cells are applied at the input of a gain cell 15.5, 15.6 which allows an adjustment of the volume of the signals 34 ', 35' by multiplying them by a gain K5, K6.
  • the electrical signals of its processed 34 "and 35" observable at the output of the cells 15.5 and 15.6 are respectively applied at the input of a transducer 39 and 41 rear for their diffusion.
  • the transducers 39 and 41 each comprise a loudspeaker 40.1 and 42.1 respectively permitting the scattering of the signals 34 ", 35".
  • the rear transducers 39, 41 comprise several loudspeakers.
  • the system has only two forward channels carrying the signals 20, 25 but no backward track carrying the signals 34 ", 35".
  • the spectral correction modules 4.1 and 4.2 are not used, the signals 2 and 3 then being directly applied at the input of the block 7 and the cells 13.5, 13.6.
  • the signals 2 and 3 are applied at the input of a module 45 of phase equalization.
  • electrical signals 2a and 3b are obtained from its left and right equalized in phase.
  • the module 45 comprises for this purpose a filter which corrects the phase defects perceived by the passengers.
  • a filter which corrects the phase defects perceived by the passengers.
  • a known signal whose phase response is zero is diffused using the left and right forward transducers 21, 26 positioned non-symmetrically with respect to a passenger, for example the driver. Indeed, the distance of one of the transducers 21, 26 to the passenger's head is different from the distance of the other transducer 21,
  • the signal emitted from the left channel via the transducer 21 is recorded by means of a microphone at the location of the head of one of the passengers and the phase response ⁇ 1 of the received left channel signal indicating variation of the phase of the received left signal as a function of the frequency.
  • the signal emitted from the right channel via the transducer 26 is recorded by means of the microphone at the location of the head of one of the passengers, and the phase response ⁇ R of the signal of the right channel received, indicating the variation of the phase of the received right signal as a function of the frequency.
  • the responses in phase ⁇ L, ⁇ R are for example calculated from the Fourier transform of the received signal.
  • the AC out-of-phase frequency bands of this phase difference are then determined, i.e., the frequency bands for which the phase difference between the received left and right signals is 180 degrees to plus or minus 20 degrees. and modulo 360 degrees.
  • the coefficients of the filters 45.1 and 45.2 of the block 45 are then parameterized, applied respectively to the electrical signal of its left 2 and to the electrical signal of its right 3, for example of allpass type ("garlic pass" in English) so as to minimize phase opposition effects in these frequency bands.
  • These all-pass filters are for example of the RII (Infinite Impulse Response) type.
  • the phase response of the all-pass filter G1 shown in FIG. 6 ranges from 0 to at least 360 degrees via an inflection point (which corresponds to the cutoff frequency) for which the phase is minus 180 degrees.
  • phase delays of 180 degrees are introduced at the points where the received signals are in phase opposition. This eliminates the frequency bands in which the received left and right signals are in phase opposition.
  • the curve C2 thus represents the phase difference when an all-pass filter of cut-off frequency f1 has been applied to one of the electrical signals of its left or right, while the curve C3 represents the phase difference when filters pass. all respectively of cut-off frequency f1 and f2 have been applied to one of the electrical signals. Note that the C1-C3 curves are spaced apart by an angle of 360 degrees.
  • the combination of two filters G2, G3 pass-all applied to the phase of the electrical signal of its sound is used. 2 and the electrical signal of its right 3.
  • the cutoff frequencies fd, fc2 frame the center frequency f1, f2 of the frequency band out of phase, as shown in FIG. 8a.
  • phase difference curve G4 (shown in dotted lines) to move away from the frequency values f1, f2 for which the received signals are in phase opposition and then to return to the C1 curve.
  • the use of these all-pass filter pairs makes it possible to locally remove the A-C bands in phase opposition.
  • off-phase frequency bands are corrected in the [20 Hz, 2000 Hz] range.
  • G5 filters of the Finite Impulse Response RIF type are used, making it possible to draw the desired phase response, this phase response being able to present the appearance of the combination of the filters.
  • these filters each have a phase response having the appearance of an inverted gate having a value of -180 degrees in a frequency band where the received left and right signals are in phase opposition.
  • the desired frequency response in the frequency domain is first plotted and an inverse Fourier transform is performed to obtain the impulse response of the filter in the time domain.
  • phase correction operation it is sufficient to perform the phase correction operation at the location of the head of one of the passengers, preferably the driver, so that the effect associated with this correction is perceived by all passengers.
  • the vehicle has a symmetry between its left and right parts, so that the perceived sound effect for the front passenger is the same as that perceived by the driver.
  • the vehicle also has a symmetry between its front and rear parts, so that the sound effect associated with the phase correction of left and right signals 2, 3 diffused at the rear is also perceived by all rear passengers.
  • phase equalization is such that when the signals 20, 34 ",
  • the delays t1-t4 are introduced in order to temporally align the pairs "tweeters / woofers" 22.1 and 22.2 as well as the pairs 27.1 and 27.2.
  • Time alignment is understood to mean introducing a delay on the signal of the nearest loudspeaker so that the sound wave emitted by the latter is perceived at the same time as the sound wave emitted by the loudspeaker the signal is not delayed.
  • FIG. 3 shows a variant in which six electrical signals 51-55 of sound input are generated from two electrical signals of sound.
  • an electrical signal from its central unit 55 is generated which comprises only the substantially in-phase spectral components of the electrical signals of its left 2 and of its right 3.
  • This signal 55 is first corrected by the spectral correction module 4.3.
  • This transducer 61 comprises one or two speakers 63 according to the vehicle model and is preferably positioned in the center of the dashboard.
  • the electrical signal 51 of its left front and the electrical signal 52 of its front right are generated by subtracting the components spectral signal 55 respectively to those of the electric signal 2 of his left and those of the electrical signal 3 of his right.
  • the electrical signals 53 and 54 of its left rear and its rear right are generated from the substantially out-of-phase components of the signals 2 and 3 electrical right and left.
  • the signals 51, 52, 53 and 54 are then processed in "driver" mode or "ail passengers” mode as described in FIGS. 1 and 2.
  • Another electric sound signal 56 may be created from the low frequency filtering of the electrical signals 2 and 3 from its left and right. Like the others, this signal 56 can be delayed by a delay cell
  • the output channels correspond to a combination of the six channels available at the input.
  • the implementation of the invention is therefore particularly advantageous with entry-level vehicles comprising only one loudspeaker per transducer.
  • the single speaker of the transducers 21 or 26 is preferably a wideband speaker.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Fittings On The Vehicle Exterior For Carrying Loads, And Devices For Holding Or Mounting Articles (AREA)
  • Stereophonic System (AREA)

Abstract

The invention relates to a method for the sound processing of a stereophonic signal inside a motor vehicle. In a first implementation ("driver" mode) the stereophonic sound source is centered in the middle of the dashboard for the 'driver' listen position. For this purpose, delays (t1-t4) are introduced into the frequency bands of the channels transmitted by the speakers, such that the driver appears to be at the center of a circle on which the car speakers are positioned. In a second implementation ("all passengers" mode), the phases of the signals of the two front channels are equalized, such that the sound source appears to be centered on the driver and the front passenger of the vehicle.

Description

Procédé de traitement sonore d'un signal stéréophonique à l'intérieur d'un véhicule automobile et véhicule automobile mettant en œuvre ce procédé Sound processing method for a stereophonic signal inside a motor vehicle and a motor vehicle implementing this method
L'invention concerne un procédé de traitement sonore d'un signal stéréophonique diffusé dans un véhicule automobile et un véhicule automobile mettant en œuvre ce procédé. L'invention a notamment pour but d'augmenter le confort d'écoute d'une bande sonore dans une voiture. Cette bande sonore peut contenir par exemple une conversation téléphonique et/ou de la musique.The invention relates to a sound processing method for a stereophonic signal broadcast in a motor vehicle and a motor vehicle implementing this method. The invention particularly aims to increase the comfort of listening to a soundtrack in a car. This soundtrack may contain for example a telephone conversation and / or music.
L'invention trouve une application particulière avantageuse dans les procédés de traitement sonore mis en œuvre avec des systèmes audiophoniques à deux voies d'entrée et à quatre, cinq ou six voies de sortie.The invention finds particular advantageous application in sound processing methods implemented with audio systems with two input channels and four, five or six output channels.
Dans les voitures, le signal stéréo composé d'un signal de son gauche (1ere voie) et d'un signal de son droit (2eme voie) généré par une source stéréophonique (telle qu'un autoradio) est diffusée sur 4 voies.In cars, the stereo signal comprising a left sound signal (1 st lane) and a signal of the right (2nd channel) generated by a stereophonic source (such as radio) is broadcast on channels 4 .
Deux voies (voies avant gauche et droite) sont diffusées par les transducteurs avant du véhicule, tandis que deux autres voies (voies arrière gauche et droite) sont diffusées par les transducteurs arrière. Une cinquième voie peut également être générée et diffusée par un transducteur situé au centre de la planche de bord.Two channels (front left and right channels) are scattered by the front transducers of the vehicle, while two other channels (left and right rear channels) are scattered by the rear transducers. A fifth channel can also be generated and broadcast by a transducer located in the center of the dashboard.
Dans la demande, on entend par transducteur un système qui transforme un signal électrique de son en un signal acoustique de son.In the application, a transducer is a system that transforms an electrical sound signal into an acoustic sound signal.
En général, un transducteur relié à une voie donnée comporte deux haut-parleurs qui diffusent respectivement la partie haute fréquence et la partie basse fréquence du signal électrique de son transporté par la voie.In general, a transducer connected to a given channel comprises two loudspeakers which diffuse respectively the high frequency part and the low frequency part of the electrical signal of its conveyed by the way.
Ainsi, un premier haut-parleur appelé « tweeter » diffuse la partie haute fréquence du signal de la voie, tandis qu'un deuxième haut-parleur appelé « woofer » diffuse la partie basse fréquence du signal de la voie. De manière connue, certains transducteurs peuvent être positionnés de sorte que le son semble provenir du bas du véhicule, ce qui ne procure pas une impression d'écoute très agréable aux passagers.Thus, a first speaker called "tweeter" broadcasts the high frequency part of the signal of the channel, while a second speaker called "woofer" broadcasts the low frequency part of the signal of the channel. In known manner, some transducers can be positioned so that the sound seems to come from the bottom of the vehicle, which does not provide a very pleasant listening impression to the passengers.
L'invention permet de résoudre ce problème en positionnant la scène sonore sur le plan des oreilles de chaque passager, en face de chaque passager et/ou au milieu de la plage de bord du véhicule. A cet effet, dans l'invention, on cherche à minimiser les effets d'opposition de phase entre les signaux gauche et droit reçus à l'endroit de la tête d'au moins un des passagers.The invention solves this problem by positioning the sound stage on the plane of the ears of each passenger, in front of each passenger and / or in the middle of the edge range of the vehicle. For this purpose, in the invention, it is sought to minimize the phase opposition effects between the left and right signals received at the head location of at least one of the passengers.
Dans une première mise en œuvre de l'invention, appelée mode « driver », on centre la source sonore stéréophonique au milieu de la planche de bord pour la position d'écoute « conducteur ». A cet effet, on introduit des délais dans les bandes de fréquence de chaque haut-parleur, de sorte que tous les haut-parleurs semblent se trouver à la distance de celui qui est le plus éloigné du conducteur. Dans une deuxième mise en œuvre, appelée mode « ail passengers », on égalise la phase résultante des signaux des voies avant et la phase des signaux des voies arrière perçues par les auditeurs, de sorte que la source sonore semble être centrée en face de chaque passager. Par ailleurs dans ce mode, des retards dans les signaux des voies avant sont introduits de manière à aligner temporellement les paires « tweeters / woofers » .In a first embodiment of the invention, called the "driver" mode, the stereophonic sound source is centered in the middle of the dashboard for the "driver" listening position. For this purpose, delays are introduced in the frequency bands of each speaker, so that all the speakers seem to be at the distance from the one which is farthest from the driver. In a second implementation, called the "garlic passengers" mode, the resultant phase of the signals of the front channels and the phase of the signals of the rear tracks perceived by the listeners are equalized, so that the sound source seems to be centered in front of each passenger. Also in this mode, delays in the front channel signals are introduced to temporally align the tweeter / woofer pairs.
L'invention concerne donc un procédé de traitement sonore d'un signal stéréophonique à l'intérieur d'un véhicule automobile, le signal stéréophonique étant composé d'un signal électrique de son gauche et d'un signal électrique de son droit, dans lequel,The invention therefore relates to a sound processing method of a stereophonic signal inside a motor vehicle, the stereophonic signal being composed of an electrical signal of its left and an electrical signal of its right, in which ,
- on égalise la phase de ces signaux électriques de son de manière à minimiser les effets d'opposition de phase dans des bandes de fréquences de ces signaux gauche et droit reçus sensiblement à l'endroit de la tête d'un des passagers, et - on diffuse le signal électrique de son gauche égalisé en phase et le signal électrique de son droit égalisé en phase respectivement à l'aide d'un transducteur avant gauche positionné dans la partie avant gauche du véhicule et d'un transducteur avant droit positionné dans la partie avant droite du véhicule. Selon une mise en oeuvre, pour minimiser les opposition de phase, on applique des filtres au signal électrique de son gauche et/ou au signal électrique de son droit, de sorte que la courbe de différence de phase entre les signaux électriques de son gauche et droit reçus à l'endroit de la tête du passager contourne les points où les signaux électriques de son gauche et droit reçus sont en opposition de phase. Selon une mise en œuvre, pour minimiser les effets d'opposition de phase, on applique des filtres passe-tout au signal gauche ou droit, ces filtres passe-tout présentant chacun une fréquence de coupure sensiblement égale à une fréquence milieu de la bande de fréquence pour laquelle les signaux électriques de son gauche et droit reçus sont en opposition de phase.the phase of these electrical sound signals is equalized so as to minimize the phase opposition effects in frequency bands of these left and right signals received substantially at the head of one of the passengers, and the electrical signal of its left equalized in phase is diffused and the electrical signal of its equalized right in phase respectively with the aid of a left front transducer positioned in the left front part of the vehicle and a right front transducer positioned in the right front part of the vehicle. According to one implementation, to minimize the phase opposition, filters are applied to the electrical signal of his left and / or the electrical signal of his right, so that the phase difference curve between the electrical signals of his left and right received at the location of the passenger's head bypasses the points where the electrical signals of his left and right received are in phase opposition. According to one implementation, to minimize the phase opposition effects, all-pass filters are applied to the left or right signal, these all-pass filters each having a cut-off frequency substantially equal to a center frequency of the band of frequency for which the electrical signals of his left and right received are in phase opposition.
Selon une mise en œuvre, pour minimiser les effets d'opposition de phase, on applique des paires de filtres passe-tout, un des filtres de la paire étant appliqué au signal électrique de son gauche et l'autre filtre de la paire étant appliqué au signal électrique de son droit, les filtres d'une paire comportant des fréquences de coupure qui encadrent une fréquence milieu de la bande de fréquence pour laquelle les signaux électriques de son gauche et droit reçus sont en opposition de phase.According to one implementation, in order to minimize the phase opposition effects, all-pass filter pairs are applied, one of the filters of the pair being applied to the electrical signal of its left and the other filter of the pair being applied. to the electrical signal of its right, the filters of a pair having cut-off frequencies which surround a middle frequency of the frequency band for which the electric signals of its left and right received are in opposition of phase.
Selon une mise en œuvre, les filtres passe-tout sont de type à Réponse Impulsionnelle Infinie (RII). Selon une mise en œuvre, les filtres sont de type RIF, à RéponseAccording to one implementation, the all-pass filters are of Infinite Impulse Response (IIR) type. According to one implementation, the filters are of the RIF type, in Response
Impulsionnelle Finie, ces filtres ayant chacun une réponse en phase présentant chacune l'allure d'une porte inversée ayant une valeur de -180 degrés sur une bande de fréquence où les signaux reçus sont en opposition de phase. Selon une mise en œuvre, on considère que les signaux électriques de son reçus sont en opposition de phase lorsque la différence de phase entre ces signaux vaut 180 degrés plus ou moins 20 degrés modulo 360 degrés.Finite Impulse, these filters each having a phase response each having the appearance of an inverted gate having a value of -180 degrees on a frequency band where the received signals are in phase opposition. According to one implementation, it is considered that the electrical signals of its receipt are in phase opposition when the phase difference between these signals is 180 degrees plus or minus 20 degrees modulo 360 degrees.
Selon une mise en œuvre, on minimise les effets d'opposition de phase pour une bande de fréquence comprise entre 20hz et 2kHz.According to one implementation, phase opposition effects are minimized for a frequency band between 20 Hz and 2 kHz.
Selon une mise en œuvre, on égalise le spectre fréquentiel des signaux électriques de son gauche et droit de manière à compenser l'acoustique à l'avant du véhicule, à l'aide d'un module de correction spectrale. Selon une mise en œuvre, on filtre des bandes de fréquence de chaque signal électrique de son, et on introduit des retards dans ces bandes de fréquence. Les retards sont choisis de manière à aligner temporellement les haut-parleurs du transducteur avant gauche ainsi que les haut-parleurs du transducteur avant droit diffusant ces bandes de fréquence. Selon une mise en œuvre, on filtre la partie basse fréquence et la partie haute fréquence de chaque signal électrique de son, les retards étant choisis de manière à aligner temporellement les haut-parleurs diffusant respectivement les parties basse et haute fréquence du signal électrique de son gauche, les retards étant choisis de manière à aligner temporellement les haut-parleurs diffusant respectivement les parties basse et haute fréquence du signal électrique de son droit.According to one embodiment, the frequency spectrum of the left and right electrical signals is equalized so as to compensate the acoustics at the front of the vehicle, using a spectral correction module. According to one embodiment, frequency bands of each electrical sound signal are filtered, and delays are introduced into these frequency bands. The delays are chosen so as to temporally align the speakers of the left front transducer as well as the speakers of the right front transducer diffusing these frequency bands. According to one embodiment, the low frequency portion and the high frequency portion of each electrical sound signal are filtered, the delays being chosen so as to temporally align the loudspeakers respectively diffusing the low and high frequency portions of the electrical signal of its sound. left, the delays being chosen so as to temporally align the speakers respectively diffusing the low and high frequency parts of the electrical signal of his right.
Selon une mise en œuvre, les délais gauche et droit appliqués sur les haut-parleurs haute fréquence sont identiques, et les délais gauche et droit appliqués sur les haut-parleurs basse fréquence sont identiques, du fait de la géométrie du véhicule. Toutefois en variante ils pourraient être différents.According to one implementation, the left and right delays applied to the high frequency loudspeakers are identical, and the left and right delays applied to the low frequency loudspeakers are identical, because of the geometry of the vehicle. However alternatively they could be different.
Selon une mise en œuvre, les bandes de fréquence des haut-parleurs correspondent aux bandes de fréquence des signaux filtrés qu'ils diffusent.According to one implementation, the frequency bands of the loudspeakers correspond to the frequency bands of the filtered signals that they broadcast.
Selon une mise en œuvre, les bandes de fréquence du signal électrique de son gauche sont combinées en un signal électrique de son gauche reconstitué, ce signal électrique de son gauche reconstitué étant diffusé par le transducteur avant gauche. Tandis que les bandes de fréquence du signal électrique de son droit sont combinées en un signal électrique de son droit reconstitué, ce signal électrique de son droit reconstitué étant diffusé par le transducteur avant droit.According to one implementation, the frequency bands of the electrical signal of its left are combined into an electrical signal of its reconstituted left, this electrical signal of its left reconstituted being diffused by the left front transducer. While the frequency bands of the electric signal of his right are combined in an electrical signal of his right reconstituted, this electric signal of his right reconstituted being diffused by the right front transducer.
Selon une mise en œuvre, les bandes de fréquence des signaux électriques de son sont ajustées en volume par des cellules de gain.According to one implementation, the frequency bands of the electrical sound signals are adjusted in volume by gain cells.
Selon une mise en œuvre, on génère un signal électrique de son central à partir des composantes spectrales en phase de signaux électriques de son gauche et droit originaux d'une source stéréophonique, ce signal électrique de son central étant diffusé, après introduction d'un retard, et ajustement en niveau et en volume, par un transducteur positionné au centre du tableau de bord.According to one implementation, an electrical signal of its central is generated from the spectral components in phase of electrical signals of its left and right originals of a stereo source, this electrical signal of its central being broadcast, after introduction of a delay, and adjustment in level and volume, by a transducer positioned in the center of the dashboard.
Selon une mise en œuvre, le signal électrique de son gauche et le signal électrique de son droit sont obtenus par soustraction des composantes spectrales du signal électrique de son central respectivement à celles du signal électrique de son gauche original et à celles du signal électrique de son droit original.According to one implementation, the electrical signal of its left and the electrical signal of its right are obtained by subtraction of the spectral components of the electrical signal from its central respectively to those of the electrical signal of its original left and those of the electrical signal of its original right.
Selon une mise en œuvre, on génère des signaux électriques de son gauche et droit arrière, à partir des composantes sensiblement hors phase des signaux électriques de son gauche et droit, ces signaux étant diffusés, après introduction d'un retard et ajustement en niveau et en volume, respectivement par un transducteur arrière gauche et un transducteur arrière droit. L'invention concerne en outre un procédé de traitement sonore d'un signal stéréophonique à l'intérieur d'un véhicule automobile, le signal stéréophonique étant composé d'un signal électrique de son gauche et d'un signal électrique de son droit, dans lequel, on filtre des bandes de fréquence de chaque signal électrique de son, et on introduit des retards dans ces bandes de fréquence.According to one implementation, electrical signals are generated from its left and right back, from substantially out of phase components. electrical signals of his left and right, these signals being diffused, after introduction of a delay and adjustment in level and volume, respectively by a left rear transducer and a right rear transducer. The invention furthermore relates to a sound processing method of a stereophonic signal inside a motor vehicle, the stereophonic signal being composed of an electrical signal of its left and of an electrical signal of its right, in which frequency bands of each electrical sound signal are filtered, and delays are introduced into these frequency bands.
Les retards sont choisis de sorte que les transducteurs diffusant ces bandes de fréquence se situent virtuellement sur un cercle, ce cercle ayant pour centre l'endroit où se situe le conducteur et présentant un rayon dont la distance est celle qui sépare le conducteur du transducteur le plus éloigné du conducteur.The delays are chosen so that the transducers diffusing these frequency bands lie virtually on a circle, this circle having as a center the location where the conductor is located and having a radius whose distance is that which separates the conductor from the transducer. further away from the driver.
Selon une mise en œuvre, on filtre la partie basse fréquence et la partie haute fréquence de chaque signal électrique de son, les transducteurs comportant chacun un haut-parleur basse fréquence et un haut-parleur haute fréquence, les retards étant alors choisis de manière à aligner temporellement les haut-parleurs diffusant respectivement les parties basse et haute fréquence du signal électrique de son gauche.According to one embodiment, the low frequency part and the high frequency part of each electrical sound signal are filtered, the transducers each comprising a low frequency loudspeaker and a high frequency loudspeaker, the delays being then chosen so as to time align the loudspeakers diffusing respectively the low and high frequency parts of the electrical signal of his left.
Les retards sont choisis de manière à aligner temporellement les haut- parleurs diffusant respectivement les parties basse et haute fréquence du signal électrique de son droit. Les délais gauche et droit appliqués sur les haut-parleurs haute fréquence sont identiques, et les délais gauche et droit appliqués sur les haut-parleurs basse fréquence sont identiques.The delays are chosen so as to temporally align the loudspeakers respectively diffusing the low and high frequency parts of the electrical signal of its right. The left and right delays applied to the high frequency speakers are identical, and the left and right delays applied to the low frequency speakers are identical.
L'invention concerne en outre un véhicule automobile comportant une source sonore générant un signal stéréo à l'intérieur d'une voiture, ce signal stéréo étant composé d'un signal électrique de son gauche et d'un signal électrique de son droit, ces signaux électrique de son gauche et droit étant traités par le procédé selon l'invention de manière à être diffusés respectivement par un transducteur avant gauche comportant uniquement un haut-parleur et un transducteur avant droit comportant uniquement un haut- parleur. Selon une réalisation, les haut-parleurs avant gauche et droit sont des haut-parleurs large-bande.The invention furthermore relates to a motor vehicle comprising a sound source generating a stereo signal inside a car, this stereo signal being composed of an electrical signal of its left and an electrical signal of its right, these electrical signals of left and right being processed by the method according to the invention so as to be respectively distributed by a front left transducer comprising only a speaker and a right front transducer comprising only a speaker. In one embodiment, the front left and right speakers are wide-band speakers.
L'invention sera mieux comprise à la lecture de la description qui suit et à l'examen des figures qui l'accompagnent. Ces figures ne sont données qu'à titre illustratif mais nullement limitatif de l'invention. Elles montrent :The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These figures are given for illustrative but not limiting of the invention. They show :
- figure 1 : une représentation schématique fonctionnelle d'un système audio mettant en œuvre le mode « driver » selon l'invention ;FIG. 1: a functional schematic representation of an audio system implementing the "driver" mode according to the invention;
- figure 2 : une représentation schématique fonctionnelle d'un système audio mettant en œuvre le mode « ail passengers » selon l'invention ; - figure 3 : une représentation schématique fonctionnelle d'un système audio selon l'invention à 2 voies d'entrée et à 6 voies de sortie ;FIG. 2: a functional schematic representation of an audio system implementing the "ail passengers" mode according to the invention; FIG. 3: a functional schematic representation of an audio system according to the invention with 2 input channels and 6 output channels;
- figures 4-5 : des représentations schématiques de l'endroit virtuel où se trouve le centre de la scène sonore respectivement lors de la mise en œuvre du procédé selon l'invention en mode « driver » et de la mise en œuvre du procédé selon l'invention en mode « ail passengers ».FIGS. 4-5: schematic representations of the virtual location where the center of the sound stage is located respectively during the implementation of the method according to the invention in "driver" mode and the implementation of the method according to the invention in "passenger passengers" mode.
- figure 6 : une représentation graphique de la différence de phase entre les signaux avant gauche et droit reçus à l'endroit de la tête de l'un des passagers avant et après correction de phase ;FIG. 6: a graphical representation of the phase difference between the front left and right signals received at the head of one of the passengers before and after phase correction;
- figure 7 : une représentation graphique d'une réponse en phase d'un filtre de type « passe-tout » utilisé pour minimiser l'opposition de phase entre les signaux acoustiques reçus à l'endroit de la tête de l'un des passager ;FIG. 7: a graphical representation of a phase response of a "pass-all" filter used to minimize the phase opposition between the acoustic signals received at the location of the head of one of the passengers ;
- figures 8 : des représentations graphiques des réponses en phase de deux filtres « passe tout » et de leur combinaison, ainsi que de la réponse en phase d'un filtre à Réponse Impulsionnelle Finie. Les éléments identiques conservent la même référence d'une figure à l'autre.FIGS. 8: graphical representations of the phase responses of two "all-pass" filters and of their combination, as well as the phase response of a Finite Impulse Response filter. Identical elements retain the same reference from one figure to another.
La figure 1 montre une représentation schématique fonctionnelle d'un système audio mettant en œuvre le mode « driver » permettant de positionner le centre de la scène sonore pour une position d'écoute à la place du conducteur du véhicule.FIG. 1 shows a functional schematic representation of an audio system implementing the "driver" mode making it possible to position the center of the sound scene for a listening position instead of the driver of the vehicle.
Le système audio selon l'invention présente deux voies d'entrée 2 et 3 et quatre voies de sortie 20, 25, 34" et 35" diffusées respectivement par les transducteurs 21 , 26, 39 et 41. Plus précisément, une source 1 sonore, telle qu'un lecteur CD, génère un signal stéréo, composé d'un signal 2 électrique de son gauche et d'un signal 3 électrique de son droit (2 voies d'entrée).The audio system according to the invention has two input channels 2 and 3 and four output channels 20, 25, 34 "and 35" respectively diffused by the transducers 21, 26, 39 and 41. More specifically, a sound source 1, such as a CD player, generates a stereo signal composed of an electrical signal 2 of its left and an electric signal 3 of its right (2 input channels).
Ces signaux 2 et 3 sont appliqués en entrée d'un module 4.1 de correction spectrale de niveau sonore. Ce module 4.1 égalise le spectre des signaux 2 et 3.These signals 2 and 3 are applied at the input of a spectral level correction module 4.1. This module 4.1 equalizes the spectrum of signals 2 and 3.
A cet effet, le module 4.1 comporte un filtre qui permet de lisser la réponse spectrale perçue des signaux électriques de son 2 et 3, de sorte que toutes les fréquences émises à une puissance donnée tendent à être perçues à un même niveau d'amplitude par le conducteur.For this purpose, the module 4.1 comprises a filter that smooths the perceived spectral response of the electrical signals of its 2 and 3, so that all the frequencies emitted at a given power tend to be perceived at the same amplitude level by the driver.
Dans une mise en oeuvre, pour calculer les coefficients du filtre du module 4.1 , par exemple des filtres de type « Peak-notch », on diffuse un signal connu à l'aide des transducteurs 21 , 26 avant gauche et droit et on enregistre le signal à l'endroit de la tête du conducteur à l'aide d'un microphone. On en déduit une fonction de transfert dite « fonction de transfert véhicule » et à partir de la fonction de transfert inverse de la « fonction de transfert véhicule », on paramètre les coefficients du filtre pour que les défauts du spectre du signal enregistré soient compensés de manière à retrouver le spectre du signal initial. Ce module 4.1 crée ainsi une forme spectrale qui compense l'acoustique du véhicule, de sorte que les signaux sonores diffusés à l'avant du véhicule par les transducteurs 21 , 26 et perçus par le conducteur (après parcours des signaux sonores à l'intérieur du véhicule) ont un spectre le plus proche possible de celui du signal sonore d'origine. On obtient en sortie du module 4.1 un signal 5 électrique de son gauche égalisé et un signal 6 électrique de son droit égalisé. Ces signaux 5 et 6 sont appliqués en entrée d'un bloc 7 permettant une correction spatiale des signaux 5 et 6.In one implementation, in order to calculate the coefficients of the filter of module 4.1, for example "peak-notch" type filters, a known signal is diffused using the transducers 21, 26 before left and right, and the signal at the driver's head using a microphone. A transfer function called "vehicle transfer function" is deduced therefrom, and from the inverse transfer function of the "vehicle transfer function", the filter coefficients are parameterized so that the defects of the spectrum of the recorded signal are compensated for. way to find the spectrum of the initial signal. This module 4.1 thus creates a spectral shape that compensates for the acoustics of the vehicle, so that the audible signals diffused at the front of the vehicle by the transducers 21, 26 and perceived by the driver (after the sound signals have been passed inside of the vehicle) have a spectrum as close as possible to that of the original sound signal. An electric signal of left equalized and an electric signal of its equalized right is obtained at the output of module 4.1. These signals 5 and 6 are applied at the input of a block 7 allowing a spatial correction of the signals 5 and 6.
Plus précisément, ces signaux 5 et 6 sont appliqués respectivement en entrée d'un filtre 9 de type passe-haut et d'un filtre 10 de type passe bas. En sortie du filtre 9, on obtient un signal 5a électrique de son gauche haute fréquence et un signal 6a électrique de son droit haute fréquence. En sortie du filtre 10, on obtient un signal 5b électrique de son gauche basse fréquence et un signal 6b électrique de son droit basse fréquence. Les fréquences de coupure des filtres 9 et 10 correspondent aux fréquences de coupure des haut-parleurs utilisés pour la diffusion des signaux filtrés. Dans une mise en œuvre, ces fréquences de coupure sont sensiblement identiques. Autrement dit, les bandes de fréquences des signaux filtrés correspondent aux bandes de fréquence des haut-parleurs diffusant ces signaux filtrés.More precisely, these signals 5 and 6 are respectively applied at the input of a high pass type filter 9 and a low pass type filter 10. At the output of the filter 9, an electric signal 5a of its left high frequency and an electric signal 6a of its high frequency right are obtained. At the output of the filter 10, an electric signal 5b of its left low frequency and an electric signal 6b of its low frequency right are obtained. The cutoff frequencies of the filters 9 and 10 correspond to the cut-off frequencies of the loudspeakers used for the diffusion of the filtered signals. In one implementation, these cutoff frequencies are substantially identical. In other words, the frequency bands of the filtered signals correspond to the frequency bands of the loudspeakers broadcasting these filtered signals.
Ici, deux haut-parleurs 22.1 , 22.2 et 27.1 , 27.2 sont reliés à chaque voie afin de diffuser respectivement les bandes de fréquence haute et les bande de fréquence basse. En variante, pour un véhicule comportant 3 haut- parleurs par voie diffusant respectivement un signal sonore haute, moyenne et basse fréquence, les signaux électriques de son gauche et droit sont chacun filtrés respectivement par 3 filtres, chacun correspondant à une des bande de fréquence de ces 3 haut-parleurs (haute, moyenne ou basse).Here, two loudspeakers 22.1, 22.2 and 27.1, 27.2 are connected to each channel in order to broadcast respectively the high frequency bands and the low frequency bands. As a variant, for a vehicle comprising three loudspeakers per channel respectively diffusing a high, medium and low frequency sound signal, the electrical signals of its left and right are each respectively filtered by 3 filters, each corresponding to one of the frequency bands of these 3 speakers (high, medium or low).
Les signaux 5a, 5b et 6a, 6b sont ensuite appliqués chacun en entrée d'une cellule 13.1-13.4 à retard. Le réglage des retards t1-t4 introduits est fait en fonction du positionnement des haut-parleurs dans la voiture, en particulier en fonction de la distance à laquelle ils se trouvent du conducteur.The signals 5a, 5b and 6a, 6b are then each applied to the input of a delay cell 13.1-13.4. The adjustment of the delays t1-t4 introduced is made according to the positioning of the speakers in the car, in particular according to the distance to which they are from the driver.
Plus précisément, on introduit des retards t1-t4 sur les signaux 5a, 5b et 6a, 6b, de sorte que tous les haut-parleurs avant semblent se situer à la distance RHPmax du transducteur 41 le plus éloigné de la tête du conducteur 62 (voir figure 4).More precisely, delays t1-t4 are introduced on the signals 5a, 5b and 6a, 6b, so that all the front loudspeakers seem to be at the distance RHPmax of the transducer 41 furthest from the driver's head 62 (FIG. see Figure 4).
A cet effet, la bande de fréquence destinée à être diffusée par le haut- parleur le plus éloigné n'est pas retardée, tandis que les bandes de fréquence diffusées par les haut-parleurs plus proches de la tête du conducteur sont retardées d'un retard tel que le son diffusé par ces haut- parleurs plus proches semble être perçu au même instant au niveau de la tête du conducteur que celui auquel le signal du haut-parleur le plus éloigné est perçu. Autrement dit, les bandes de fréquence sont retardées de manière que les sons diffusés par tous les haut-parleurs sont perçus au même instant à l'endroit de la tête du conducteur.For this purpose, the frequency band intended to be broadcast by the farthest speaker is not delayed, whereas the frequency bands broadcast by the loudspeakers closer to the driver's head are delayed by one. delay such that the sound broadcast by these closer speakers seems to be perceived at the same time at the driver's head than that to which the signal of the farthest speaker is perceived. In other words, the frequency bands are delayed so that the sounds broadcast by all the speakers are perceived at the same time at the location of the driver's head.
Le conducteur 62 se trouve alors au centre d'un cercle C de rayon RHPmax sur lequel les images S1-S4 des haut-parleurs 22.1 , 22.2, 27.1 , 27.2 se trouvent, comme représenté à la figure 4.The conductor 62 is then in the center of a circle C of radius RHPmax on which the images S1-S4 of the loudspeakers 22.1, 22.2, 27.1, 27.2 are located, as represented in FIG. 4.
Dans la pratique, on mesure d'abord la distance qui sépare chaque haut-parleur du conducteur et on introduit un retard en fonction de cette mesure dans les bandes de fréquence diffusées par les haut-parleurs autres que celui qui est le plus éloigné, de sorte que tous les haut-parleurs semblent se situer à la distance RHPmax du haut-parleur le plus éloigné.In practice, the distance between each loudspeaker and the driver is first measured and a delay is introduced according to this measurement in the frequency bands broadcast by the speakers other than the one furthest away, so that all the speakers appear to be at the RHPmax distance of the farthest speaker.
Dans le mode driver, le fait de placer tous les transducteurs à une même distance du conducteur (au moins un des passagers) annule complètement les effets d'opposition de phase peu agréables à l'oreille.In the driver mode, placing all the transducers at the same distance from the driver (at least one of the passengers) completely cancels the phase opposition effects that are unpleasant to the ear.
Les signaux 5a', 6a', 5b' et 6b' retardés observables en sortie des cellules 13.1-13.4 sont appliqués en entrée de cellules 15.1-15.4 de gain.The delayed signals 5a ', 6a', 5b 'and 6b' observable at the output of the cells 13.1-13.4 are applied at the input of cells 15.1-15.4 gain.
Ces cellules 15.1-15.4 permettent un réglage du volume des signaux sonores haute et basse fréquences. A cet effet, les signaux retardés sont multipliés par des coefficients K1-K4, par exemple compris entre 0 et 1.These cells 15.1-15.4 allow an adjustment of the volume of the high and low frequency sound signals. For this purpose, the delayed signals are multiplied by coefficients K1-K4, for example between 0 and 1.
Le signal 5a" électrique de son gauche haute fréquence traité observable en sortie de la cellule 15.1 , et le signal 5b" électrique de son gauche basse fréquence traité observable en sortie de la cellule 15.3 sont appliqués en entrée d'un sommateur 17.1.The electric signal 5a of its left high-frequency processed signal observable at the output of the cell 15.1, and the electric signal 5b "of its left low frequency processed observable at the output of the cell 15.3 are applied at the input of an adder 17.1.
En sortie de ce sommateur 17.1 est alors observable un signal 20 électrique de son gauche reconstitué. Ce signal 20 correspond à la voie avant gauche (première voie de sortie) diffusée par un transducteur 21 comportant deux haut-parleurs 22.1 et 22.2 positionnés dans la partie avant gauche du véhicule.At the output of this adder 17.1 is then observable an electrical signal 20 of his left reconstituted. This signal 20 corresponds to the left front channel (first output channel) diffused by a transducer 21 having two speakers 22.1 and 22.2 positioned in the left front part of the vehicle.
Le premier haut-parleur 22.1 (le « tweeter ») diffuse la partie haute fréquence du signal 20, tandis que le deuxième haut-parleur 22.2 (« le woofer ») diffuse la partie basse fréquence du signal 20.The first speaker 22.1 (the "tweeter") broadcasts the high frequency portion of the signal 20, while the second speaker 22.2 ("the woofer") broadcasts the low frequency portion of the signal 20.
De manière analogue, le signal 6a" électrique de son droit haute fréquence traité observable en sortie de la cellule 15.2, et le signal 6b" électrique de son droit basse fréquence traité observable en sortie de la cellule 15.4 sont appliqués en entrée d'un sommateur 17.2.Similarly, the electrical signal 6a of its processed high frequency right observed at the output of the cell 15.2, and the electric signal 6b of its observed low frequency right observed at the output of the cell 15.4 are applied at the input of an adder. 17.2.
En sortie de ce sommateur 17.2 est alors observable un signal 25 électrique de son gauche reconstitué. Ce signal 25 correspond à la voie avant droite (deuxième voie de sortie) diffusée par un transducteur 26 comportant deux haut-parleurs 27.1 et 27.2 positionnés dans la partie avant droite du véhicule.At the output of this adder 17.2 is then observable an electrical signal of his left reconstituted. This signal 25 corresponds to the right front channel (second output channel) diffused by a transducer 26 comprising two speakers 27.1 and 27.2 positioned in the right front part of the vehicle.
Le premier haut-parleur 27.1 (le « tweeter ») diffuse la partie haute fréquence du signal 25, tandis que le deuxième haut-parleur 27.2 (« le woofer ») diffuse la partie basse fréquence du signal 25. Les parties haute fréquence et basse fréquence des signaux 20 et 25 diffusées par les haut-parleurs 22.1 , 22.2 et 27.1 , 27.2 correspondent, comme on l'a vu, aux bandes de fréquence filtrées par les filtres haute fréquence et basse fréquence 9 et 10. En variante, les signaux 5a" et 6a" électriques de son haute fréquence sont diffusés respectivement par un transducteur 29 et 30 ne comportant qu'un haut-parleur 31 , 32 ayant une bande de fréquence haute. Tandis que les transducteurs 21 et 26 diffusent directement les signaux 5b" et 6b". On a alors un haut-parleur par voie et non plus deux haut-parleurs par voie. On supprime dans ce cas les sommateurs 17.1 et 17.2.The first speaker 27.1 (the "tweeter") broadcasts the high frequency portion of the signal 25, while the second speaker 27.2 ("the woofer") broadcasts the low frequency portion of the signal 25. The high frequency and low frequency portions of the signals 20 and 25 diffused by the loudspeakers 22.1, 22.2 and 27.1, 27.2 correspond, as we have seen, to the frequency bands filtered by the high frequency and low frequency filters 9 and 10. In a variant, the high-frequency signals 5a "and 6a" of electrical sound are diffused respectively by a transducer 29 and 30 comprising only a loudspeaker 31, 32 having a high frequency band. While the transducers 21 and 26 directly broadcast the signals 5b "and 6b". We then have one loudspeaker per channel and no longer two loudspeakers per channel. In this case, the summers 17.1 and 17.2 are suppressed.
Par ailleurs, les signaux 2 et 3 sont appliqués en entrée d'un deuxième module 4.2 de correction spectrale de niveau. De la même manière que le module 4.1 pour les voies 20, 25 avant du véhicule, ce module 4.2 compense l'acoustique du véhicule pour les voies 34", 35" arrière du véhicule. En sortie du module 4.2, sont observables des signaux 34, 35 électriques de son gauche et droit égalisés.Moreover, the signals 2 and 3 are applied at the input of a second spectral correction module 4.2. In the same way as the module 4.1 for the channels 20, 25 front of the vehicle, this module 4.2 compensates the vehicle acoustics for the channels 34 ", 35" rear of the vehicle. At the output of module 4.2, are observed electrical signals 34, 35 of its left and right equalized.
Ces signaux 34 et 35 sont appliqués en entrée d'un deuxième bloc 7bis assurant une correction spatiale des signaux 34 et 35.These signals 34 and 35 are applied at the input of a second block 7bis ensuring a spatial correction of the signals 34 and 35.
Plus précisément, ces signaux 34 et 35 (troisième et quatrième voie de sortie) sont respectivement appliqués en entrée des cellules 13.5 et 13.6 à retard. Ces cellules 13.5, 13.6 introduisent chacune un retard t5 et t6 dans les signaux 34 et 35, de sorte que tous les transducteurs semblent être virtuellement à la distance RHPmax du haut-parleur le plus éloigné du conducteur, comme illustré par la figure 4. Les signaux 34' et 35' observables en sortie des cellules de retard sont appliqués en entrée d'une cellule 15.5, 15.6 de gain qui permet un réglage du volume des signaux 34', 35' en les multipliant par un gain K5, K6.More precisely, these signals 34 and 35 (third and fourth output channels) are respectively applied at the input of delay cells 13.5 and 13.6. These cells 13.5, 13.6 each introduce a delay t5 and t6 in the signals 34 and 35, so that all the transducers seem to be virtually at the distance RHPmax of the loudspeaker farthest from the conductor, as shown in FIG. signals 34 'and 35' observable at the output of the delay cells are applied at the input of a gain cell 15.5, 15.6 which allows an adjustment of the volume of the signals 34 ', 35' by multiplying them by a gain K5, K6.
Les signaux électriques de son traité 34" et 35" observables en sortie des cellules 15.5 et 15.6 sont respectivement appliqués en entrée d'un transducteur 39 et 41 arrière pour leur diffusion.The electrical signals of its processed 34 "and 35" observable at the output of the cells 15.5 and 15.6 are respectively applied at the input of a transducer 39 and 41 rear for their diffusion.
Les transducteurs 39 et 41 comportent chacun un haut-parleur 40.1 et 42.1 permettant respectivement la diffusion des signaux 34", 35".The transducers 39 and 41 each comprise a loudspeaker 40.1 and 42.1 respectively permitting the scattering of the signals 34 ", 35".
En variante, les transducteurs arrière 39, 41 comportent plusieurs haut-parleurs. En variante, le système n'a que deux voies avant transportant les signaux 20, 25 mais pas de voie arrière transportant les signaux 34", 35".In a variant, the rear transducers 39, 41 comprise several loudspeakers. Alternatively, the system has only two forward channels carrying the signals 20, 25 but no backward track carrying the signals 34 ", 35".
En variante, les modules de correction spectrale 4.1 et 4.2 ne sont pas utilisés, les signaux 2 et 3 étant alors directement appliqués en entrée du bloc 7 et des cellules 13.5, 13.6.As a variant, the spectral correction modules 4.1 and 4.2 are not used, the signals 2 and 3 then being directly applied at the input of the block 7 and the cells 13.5, 13.6.
Dans le mode de réalisation « ail passengers » de la figure 2, avant d'être appliqués en entrée des modules 4.1 et 4.2, les signaux 2 et 3 sont appliqués en entrée d'un module 45 d'égalisation de phase. En sortie du module 45, on obtient des signaux 2bis et 3bis électrique de son gauche et droit égalisés en phase. Ces signaux 2bis et 3bis sont alors traités par les blocs 4.1 et 7 avant d'être diffusés par les transducteurs avant 21 et 26 et traités par les blocs 4.2 et 7bis avant d'être diffusés par les transducteurs arrière 39 et 41.In the embodiment "ail passengers" of Figure 2, before being applied to the input of the modules 4.1 and 4.2, the signals 2 and 3 are applied at the input of a module 45 of phase equalization. At the output of the module 45, electrical signals 2a and 3b are obtained from its left and right equalized in phase. These signals 2bis and 3bis are then processed by the blocks 4.1 and 7 before being diffused by the front transducers 21 and 26 and processed by the blocks 4.2 and 7bis before being diffused by the rear transducers 39 and 41.
Le module 45 comporte à cet effet un filtre qui corrige les défauts de phase perçus par les passagers. Dans une mise œuvre, pour calculer les coefficients du filtre du module 45, on diffuse un signal connu dont la réponse en phase est nulle à l'aide des transducteurs 21 , 26 avant gauche et droit positionnés de manière non-symétrique par rapport à un passager, par exemple le conducteur. En effet, la distance d'un des transducteurs 21 , 26 à la tête du passager est différente de la distance de l'autre transducteur 21 ,The module 45 comprises for this purpose a filter which corrects the phase defects perceived by the passengers. In an implementation, in order to calculate the coefficients of the filter of the module 45, a known signal whose phase response is zero is diffused using the left and right forward transducers 21, 26 positioned non-symmetrically with respect to a passenger, for example the driver. Indeed, the distance of one of the transducers 21, 26 to the passenger's head is different from the distance of the other transducer 21,
26 à la tête du passager.26 at the passenger's head.
On enregistre à l'aide d'un microphone à l'endroit de la tête de l'un des passagers le signal émis du canal gauche via le transducteur 21 et on en déduit la réponse en phase φl_ du signal du canal gauche reçu indiquant la variation de la phase du signal gauche reçu en fonction de la fréquence.The signal emitted from the left channel via the transducer 21 is recorded by means of a microphone at the location of the head of one of the passengers and the phase response φ1 of the received left channel signal indicating variation of the phase of the received left signal as a function of the frequency.
De même, on enregistre à l'aide du microphone à l'endroit de la tête de l'un des passagers le signal émis du canal droit via le transducteur 26 et on en déduit la réponse en phase φR du signal du canal droit reçu indiquant la variation de la phase du signal droit reçu en fonction de la fréquence. Les réponses en phase φL, φR sont par exemple calculées à partir de la transformée de Fourier du signal reçu.Likewise, the signal emitted from the right channel via the transducer 26 is recorded by means of the microphone at the location of the head of one of the passengers, and the phase response φR of the signal of the right channel received, indicating the variation of the phase of the received right signal as a function of the frequency. The responses in phase φL, φR are for example calculated from the Fourier transform of the received signal.
On en déduit ensuite la différence de phase φL-φR entre les signaux gauche et droit reçus par le microphone en faisant la soustraction entre les deux réponses de phase obtenues φL-φR. La courbe C1 représentant cette différence de phase en fonction de la fréquence présente une allure linéaire, comme montré sur la figure 6.We then deduce the phase difference φL-φR between the left and right signals received by the microphone by subtracting between the two phase responses obtained φL-φR. The curve C1 representing this phase difference as a function of frequency has a linear appearance, as shown in FIG.
On détermine ensuite les bandes A-C de fréquence hors-phase de cette différence de phase, c'est-à-dire les bandes de fréquence pour lesquelles la différence de phase entre les signaux gauche et droit reçus vaut 180 degrés à plus ou moins 20 degrés et modulo 360 degrés.The AC out-of-phase frequency bands of this phase difference are then determined, i.e., the frequency bands for which the phase difference between the received left and right signals is 180 degrees to plus or minus 20 degrees. and modulo 360 degrees.
On paramètre ensuite les coefficients des filtres 45.1 et 45.2 du bloc 45, appliqués respectivement au signal électrique de son gauche 2 et au signal électrique de son droit 3, par exemple de type passe-tout (« ail pass » en anglais) de manière à minimiser les effets d'opposition de phase dans ces bandes de fréquence. Ces filtres passe-tout sont par exemple de type RII (à Réponse Impulsionnelle Infinie).The coefficients of the filters 45.1 and 45.2 of the block 45 are then parameterized, applied respectively to the electrical signal of its left 2 and to the electrical signal of its right 3, for example of allpass type ("garlic pass" in English) so as to minimize phase opposition effects in these frequency bands. These all-pass filters are for example of the RII (Infinite Impulse Response) type.
Le fait de minimiser les oppositions de phase entre le signal reçu du canal gauche et le signal reçu du canal droit donne l'impression à l'ensemble des passagers du véhicule que les transducteurs 21 , 26 sont positionnés de manière symétrique par rapport à chacun d'eux, ce qui augmente leur confort d'écoute.Minimizing the phase oppositions between the signal received from the left channel and the signal received from the right channel gives the impression to all of the passengers of the vehicle that the transducers 21, 26 are positioned symmetrically with respect to each one of them. them, which increases their listening comfort.
La réponse en phase du filtre passe-tout G1 représentée figure 6 va de 0 à moins 360 degrés en passant par un point d'inflexion (qui correspond à la fréquence de coupure) pour lequel la phase vaut moins 180 degrés.The phase response of the all-pass filter G1 shown in FIG. 6 ranges from 0 to at least 360 degrees via an inflection point (which corresponds to the cutoff frequency) for which the phase is minus 180 degrees.
En appliquant sur un des signaux électriques 2, 3 des filtres passe- tout dont la fréquence de coupure fc est égale à la fréquence milieu f1 , f2 de la bande hors phase considérée, on introduit des retards de phase de 180 degrés aux points où les signaux reçus sont en opposition de phase. On élimine ainsi les bandes de fréquence dans lesquelles les signaux gauche et droit reçus sont en opposition de phase.By applying to one of the electrical signals 2, 3 all-pass filters whose cut-off frequency fc is equal to the center frequency f1, f2 of the non-phase band considered, phase delays of 180 degrees are introduced at the points where the received signals are in phase opposition. This eliminates the frequency bands in which the received left and right signals are in phase opposition.
La courbe C2 représente ainsi la différence de phase lorsqu'un filtre passe-tout de fréquence de coupure f1 a été appliqué sur un des signaux électrique de son gauche ou droit, tandis que la courbe C3 représente la différence de phase lorsque des filtres passe-tout respectivement de fréquence de coupure f1 et f2 ont été appliqués sur un des signaux électriques. On remarque que les courbes C1-C3 sont espacées entre elles d'un angle de 360 degrés.The curve C2 thus represents the phase difference when an all-pass filter of cut-off frequency f1 has been applied to one of the electrical signals of its left or right, while the curve C3 represents the phase difference when filters pass. all respectively of cut-off frequency f1 and f2 have been applied to one of the electrical signals. Note that the C1-C3 curves are spaced apart by an angle of 360 degrees.
En variante, on utilise la combinaison de deux filtres G2, G3 passe- tout appliqués respectivement sur la phase du signal électrique de son gauche 2 et du signal électrique de son droit 3. Les fréquences de coupure fd , fc2 encadrent la fréquence milieu f1 , f2 de la bande de fréquence hors phase, comme montré sur la figure 8a.As a variant, the combination of two filters G2, G3 pass-all applied to the phase of the electrical signal of its sound is used. 2 and the electrical signal of its right 3. The cutoff frequencies fd, fc2 frame the center frequency f1, f2 of the frequency band out of phase, as shown in FIG. 8a.
La combinaison de ces filtres G2 et G3 permet d'obtenir un filtre G4 montré figure 8b présentant une réponse en phase qui de zéro descend progressivement jusqu'à un minimal de moins 180 degrés et remonte ensuite jusqu'à zéro (allure d'une courbe de Gauss inversée), suivant ainsi la valeur de la différence de phase D entre les courbes G2 et G3 de la figure 8a.The combination of these filters G2 and G3 makes it possible to obtain a filter G4 shown in FIG. 8b presenting a phase response that zero progressively descends to a minimum of minus 180 degrees and then goes back to zero (curve shape inverted Gauss), thus following the value of the phase difference D between the curves G2 and G3 of FIG. 8a.
L'application de ces paires de filtres permet ainsi à la courbe G4 de différence de phase (représentée en pointillés) de s'éloigner localement des valeurs de fréquences f1 , f2 pour lesquelles les signaux reçus sont en opposition de phase pour ensuite revenir à la courbe C1. Autrement dit, l'utilisation de ces paires de filtres passe-tout permet de supprimer localement les bandes A-C en opposition de phase. Dans la pratique, on corrige les bandes de fréquences hors-phase dans l'intervalle [20 Hz, 2000 Hz].The application of these pairs of filters thus makes it possible for the phase difference curve G4 (shown in dotted lines) to move away from the frequency values f1, f2 for which the received signals are in phase opposition and then to return to the C1 curve. In other words, the use of these all-pass filter pairs makes it possible to locally remove the A-C bands in phase opposition. In practice, off-phase frequency bands are corrected in the [20 Hz, 2000 Hz] range.
En variante, on utilise des filtres G5 de type RIF à Réponse Impulsionnelle Finie permettant de dessiner la réponse en phase souhaitée, cette réponse en phase pouvant présenter l'allure de la combinaison des filtres passe tout. De préférence, ces filtres présentent chacun une réponse en phase ayant l'allure d'une porte inversée ayant une valeur de -180 degrés sur une bande de fréquence où les signaux gauche et droit reçus sont en opposition de phase.As a variant, G5 filters of the Finite Impulse Response RIF type are used, making it possible to draw the desired phase response, this phase response being able to present the appearance of the combination of the filters. Preferably, these filters each have a phase response having the appearance of an inverted gate having a value of -180 degrees in a frequency band where the received left and right signals are in phase opposition.
Dans la pratique, pour élaborer de tels filtres RIF, on trace d'abord la réponse en fréquence souhaitée dans le domaine fréquentiel et on effectue une transformée de Fourier inverse pour obtenir la réponse impulsionnelle du filtre dans le domaine temporel.In practice, in order to develop such FIR filters, the desired frequency response in the frequency domain is first plotted and an inverse Fourier transform is performed to obtain the impulse response of the filter in the time domain.
Il suffit d'effectuer l'opération de correction de phase à l'endroit de la tête d'un des passagers, de préférence le conducteur, pour que l'effet associé à cette correction soit perçu par tous les passagers.It is sufficient to perform the phase correction operation at the location of the head of one of the passengers, preferably the driver, so that the effect associated with this correction is perceived by all passengers.
En effet, le véhicule présente une symétrie entre ses parties gauche et droite, de sorte que l'effet sonore perçu pour le passager avant est le même que celui perçu par le conducteur. En outre, le véhicule présente également une symétrie entre ses parties avant et arrière, de sorte que l'effet sonore associé à la correction de phase des signaux gauche et droit 2, 3 diffusés à l'arrière est également perçu par tous les passagers arrière.Indeed, the vehicle has a symmetry between its left and right parts, so that the perceived sound effect for the front passenger is the same as that perceived by the driver. In addition, the vehicle also has a symmetry between its front and rear parts, so that the sound effect associated with the phase correction of left and right signals 2, 3 diffused at the rear is also perceived by all rear passengers.
Toutefois, il serait envisageable de répéter l'opération de correction de phase à l'arrière pour ajuster les réglages du procédé selon l'invention. Ainsi l'égalisation de phase est telle que lorsque les signaux 20, 34",However, it would be conceivable to repeat the phase correction operation at the rear to adjust the settings of the method according to the invention. Thus the phase equalization is such that when the signals 20, 34 ",
35" et 25 sont diffusés, le passager perçoit le centre de la scène sonore 67, 68, 69, 71 en face de lui, comme représenté sur la figure 5.35 "and 25 are broadcast, the passenger perceives the center of the sound stage 67, 68, 69, 71 in front of him, as shown in FIG.
Dans le mode de réalisation « ail passengers » les retards t1-t4 sont introduits de manière à aligner temporellement les paires « tweeters / woofers » 22.1 et 22.2 ainsi que les paires 27.1 et 27.2. On entend par alignement temporel le fait d'introduire un retard sur le signal du haut-parleur le plus proche de sorte que l'onde sonore émise par ce dernier est perçue au même instant que l'onde sonore émise par le haut-parleur dont le signal est non retardé. Les retards t1 et t2 puis t3 et t4 sont alors identiques deux à deux, c'est à dire que les délais gauche et droit appliqués sur les tweeters 22.1 , 27.1 sont identiques (t1 =t2) et les délais gauche et droit appliqués sur les woofers 22.2, 27.2 sont identiques (t3=t4).In the "ail passengers" embodiment, the delays t1-t4 are introduced in order to temporally align the pairs "tweeters / woofers" 22.1 and 22.2 as well as the pairs 27.1 and 27.2. Time alignment is understood to mean introducing a delay on the signal of the nearest loudspeaker so that the sound wave emitted by the latter is perceived at the same time as the sound wave emitted by the loudspeaker the signal is not delayed. The delays t1 and t2 then t3 and t4 are then identical two by two, ie the left and right delays applied to the tweeters 22.1, 27.1 are identical (t1 = t2) and the left and right delays applied to the woofers 22.2, 27.2 are identical (t3 = t4).
La figure 3 montre une variante dans laquelle on génère six signaux 51-55 électriques de son d'entrée à partir de deux signaux électriques de sonFIG. 3 shows a variant in which six electrical signals 51-55 of sound input are generated from two electrical signals of sound.
2 et 3 d'entrée. Ces signaux sont générés en mettant en oeuvre le procédé de traitement du son décrit dans la demande de brevet publiée sous le numéro WO-2006/125931.2 and 3 input. These signals are generated by implementing the sound processing method described in the patent application published under the number WO-2006/125931.
Plus précisément, on génère un signal électrique de son central 55 qui comporte uniquement les composantes spectrales sensiblement en phase des signaux électriques de son gauche 2 et de son droit 3. Ce signal 55 est d'abord corrigé par le module 4.3 de correction spectrale.More precisely, an electrical signal from its central unit 55 is generated which comprises only the substantially in-phase spectral components of the electrical signals of its left 2 and of its right 3. This signal 55 is first corrected by the spectral correction module 4.3.
Puis le signal obtenu est retardé par la cellule 13.7 d'un retard t7, et est ajusté en volume par la cellule 15.7 pour être ensuite diffusé par le transducteur 61. Ce transducteur 61 comporte un ou deux haut-parleurs 63 suivant le modèle de véhicule et est positionné de préférence au centre du tableau de bord.Then the signal obtained is delayed by the cell 13.7 by a delay t7, and is adjusted in volume by the cell 15.7 to be then diffused by the transducer 61. This transducer 61 comprises one or two speakers 63 according to the vehicle model and is preferably positioned in the center of the dashboard.
Par ailleurs, on génère le signal 51 électrique de son gauche avant et le signal 52 électrique de son droit avant en soustrayant les composantes spectrales du signal 55 respectivement à celles du signal 2 électrique de son gauche et à celles du signal 3 électrique de son droit.Moreover, the electrical signal 51 of its left front and the electrical signal 52 of its front right are generated by subtracting the components spectral signal 55 respectively to those of the electric signal 2 of his left and those of the electrical signal 3 of his right.
Les signaux 53 et 54 électriques de son gauche arrière et de son droit arrière sont générés à partir des composantes sensiblement hors-phase des signaux 2 et 3 électriques de son droit et gauche.The electrical signals 53 and 54 of its left rear and its rear right are generated from the substantially out-of-phase components of the signals 2 and 3 electrical right and left.
Les signaux 51 , 52, 53 et 54 sont ensuite traités en mode « driver » ou en mode « ail passengers » comme décrit à la figure 1 et 2.The signals 51, 52, 53 and 54 are then processed in "driver" mode or "ail passengers" mode as described in FIGS. 1 and 2.
Un autre signal 56 électrique de son peut être créé à partir du filtrage basse fréquence des signaux 2 et 3 électriques de son gauche et droit. Comme les autres, ce signal 56 peut être retardé par une cellule à retardAnother electric sound signal 56 may be created from the low frequency filtering of the electrical signals 2 and 3 from its left and right. Like the others, this signal 56 can be delayed by a delay cell
13.8 et ajusté en volume par une cellule 15.8 avant d'être diffusé par un transducteur 64 comprenant un haut-parleur basse fréquence 65.13.8 and adjusted in volume by a cell 15.8 before being diffused by a transducer 64 comprising a low frequency speaker 65.
En variante, on dispose déjà d'une source telle qu'un DVD à 6 signaux d'entrée (6 voies d'entrée). En variante, lorsqu'on dispose de 6 voies d'entrée mais uniquement de 2 ou 4 voies de sortie, les voies de sorties correspondent à une combinaison des six voies disponibles en entrée.Alternatively, there is already a source such as a DVD with 6 input signals (6 input channels). As a variant, when there are 6 input channels but only 2 or 4 output channels, the output channels correspond to a combination of the six channels available at the input.
On s'est aperçu que avec les modes « ail passengers » et « driver » le rendu sonore avec l'utilisation de transducteurs 21 , 26 et 39, 42 à un haut- parleur est au moins similaire au rendu sonore sans traitement mais avec plusieurs haut-parleurs par transducteurs.It was found that with the modes "passenger garlic" and "driver" sound rendering with the use of transducers 21, 26 and 39, 42 to a speaker is at least similar to the sound without treatment but with several speakers by transducers.
La mise en œuvre de l'invention est donc particulièrement intéressante avec les véhicules d'entrée de gamme comportant uniquement un haut-parleur par transducteur. Dans ce cas, l'unique haut-parleur des transducteurs 21 ou 26 est de préférence un haut-parleur large bande. The implementation of the invention is therefore particularly advantageous with entry-level vehicles comprising only one loudspeaker per transducer. In this case, the single speaker of the transducers 21 or 26 is preferably a wideband speaker.

Claims

REVENDICATIONS
1. Procédé de traitement sonore d'un signal (2, 3) stéréophonique à l'intérieur d'un véhicule automobile, le signal stéréophonique étant composé d'un signal (2) électrique de son gauche et d'un signal (3) électrique de son droit, caractérisé en ce que,1. Process for sound processing a stereophonic signal (2, 3) inside a motor vehicle, the stereophonic signal being composed of an electric signal (2) of its left and a signal (3) its right, characterized in that,
- on diffuse un signal (2) électrique de son gauche et d'un signal (3) électrique de son droit à l'aide de transducteurs (21 , 26) avant gauche et droit, - on enregistre à l'aide d'un microphone à l'endroit de la tête de l'un des passagers le signal émis par le transducteur gauche et on en déduit la réponse en phase (φl_) du signal du canal gauche reçu indiquant la variation de la phase du signal gauche reçu en fonction de la fréquence,an electric signal (2) is broadcast from its left and an electric signal (3) from its right by means of left and right forward transducers (21, 26); microphone at the location of the head of one of the passengers the signal emitted by the left transducer and we deduce the phase response (φl_) of the signal of the left channel received indicating the variation of the phase of the left signal received in function the frequency,
- on enregistre à l'aide du microphone à l'endroit de la tête de l'un des passagers le signal émis par le transducteur droit et on en déduit la réponse en phase (φR) du signal du canal droit reçu indiquant la variation de la phase du signal droit reçu en fonction de la fréquence,the signal emitted by the right transducer is recorded by means of the microphone at the location of the head of one of the passengers and the phase response (φR) of the received right channel signal indicating the variation of phase of the received right signal as a function of frequency,
- on en déduit ensuite la différence de phase (φL-φR) entre les signaux gauche et droit reçus par le microphone en faisant la soustraction entre les deux réponses de phase obtenues (φL-φR), etthe phase difference (φL-φR) between the left and right signals received by the microphone is then deduced by subtracting between the two phase responses obtained (φL-φR), and
-on modifie les phases du signal (2) électrique de son gauche et du signal (3) électrique de son droit de manière à minimiser les oppositions de phases entre le signal reçu du canal gauche et le signal reçu du canal droit à l'endroit de la tête du passager.the phases of the electric signal (2) of its left and of the electrical signal (3) of its right are modified so as to minimize the phase oppositions between the signal received from the left channel and the signal received from the right channel at the location of the passenger's head.
2. Procédé selon la revendication 1 , caractérisé en ce que :2. Method according to claim 1, characterized in that:
- on minimise les effets d'opposition de phase entre le signal reçu du canal gauche et le signal reçu du canal droit à l'endroit de la tête de tous les passagers du véhicule.the phase opposition effects between the signal received from the left channel and the signal received from the right channel at the head of all the passengers of the vehicle are minimized.
3. Procédé selon la revendication 2, caractérisé en ce que, pour minimiser les opposition de phase, on applique des filtres au signal électrique de son gauche (2) et/ou au signal électrique de son droit (3), de sorte que la courbe de différence de phase (φL-φR) entre les signaux électriques de son gauche et droit (2, 3) reçus à l'endroit de la tête du passager contourne les points où les signaux électriques de son gauche et droit reçus sont en opposition de phase.3. Method according to claim 2, characterized in that, to minimize the phase opposition, filters are applied to the electrical signal of its left (2) and / or the electrical signal of its right (3), so that the phase difference curve (φL-φR) between the electrical signals of his left and right (2, 3) received at the location of the passenger's head bypasses the points where the electrical signals of his left and right received are in phase opposition.
4. Procédé selon l'une des revendications 1 à 3, caractérisé en ce que pour minimiser les effets d'opposition de phase, on applique des filtres passe-tout au signal gauche ou droit (2, 3), ces filtres passe-tout présentant chacun une fréquence de coupure (fc) sensiblement égale à une fréquence (f1 , f2) milieu de la bande de fréquence (A-C) pour laquelle les signaux électriques de son gauche (2) et droit (3) reçus sont en opposition de phase.4. Method according to one of claims 1 to 3, characterized in that to minimize the effects of phase opposition, all-pass filters are applied to the left or right signal (2, 3), these all-pass filters each having a cut-off frequency (fc) substantially equal to a frequency (f1, f2) medium of the frequency band (AC) for which the electrical signals of its left (2) and right (3) received are in phase opposition .
5. Procédé selon l'une des revendications 1 à 4, caractérisé en ce que pour minimiser les effets d'opposition de phase, on applique des paires de filtres passe-tout, un des filtres de la paire étant appliqué au signal électrique de son gauche et l'autre filtre de la paire étant appliqué au signal électrique de son droit, les filtres d'une paire comportant des fréquences (fd , fc2) de coupure qui encadrent une fréquence (f1 ) milieu de la bande de fréquence (A-C) pour laquelle les signaux électriques de son gauche (2) et droit (3) reçus sont en opposition de phase.5. Method according to one of claims 1 to 4, characterized in that to minimize the phase opposition effects are applied pairs of all-pass filters, one of the filters of the pair being applied to the electrical signal of his left and the other filter of the pair being applied to the electrical signal of its right, the filters of a pair having cutoff frequencies (fd, fc2) which surround a frequency (f1) middle of the frequency band (AC) for which the electrical signals of his left (2) and right (3) received are in opposition of phase.
6. Procédé selon la revendication 4 ou 5, caractérisé en ce que les filtres passe-tout sont de type à Réponse Impulsionnelle Infinie (RII).6. Method according to claim 4 or 5, characterized in that the all-pass filters are of Infinite Impulse Response (IIR) type.
7. Procédé selon la revendication 3, caractérisé en ce que les filtres sont de type RIF, à Réponse Impulsionnelle Finie, ces filtres ayant chacun une réponse en phase présentant chacune l'allure d'une porte inversée ayant une valeur de -180 degrés sur une bande de fréquence où les signaux reçus sont en opposition de phase.7. Method according to claim 3, characterized in that the filters are of RIF type, Finite Impulse Response, these filters each having a phase response each having the appearance of an inverted gate having a value of -180 degrees on a frequency band where the received signals are in phase opposition.
8. Procédé selon l'une des revendications 3 à 7, caractérisé en ce que on considère que les signaux électriques de son reçus sont en opposition de phase lorsque la différence de phase entre ces signaux vaut 180 degrés plus ou moins 20 degrés modulo 360 degrés. 8. Method according to one of claims 3 to 7, characterized in that it is considered that the electrical signals of his receipt are in phase opposition when the phase difference between these signals is 180 degrees plus or minus 20 degrees modulo 360 degrees .
9. Procédé selon l'une des revendications 1 à 8, caractérisé en ce que on minimise les effets d'opposition de phase pour une bande de fréquence comprise entre 20hz et 2kHz.9. Method according to one of claims 1 to 8, characterized in that the phase opposition effects are minimized for a frequency band between 20hz and 2kHz.
10. Procédé selon l'une des revendications 1 à 9, dans lequel :10. Process according to one of claims 1 to 9, in which:
- on égalise le spectre fréquentiel des signaux (2, 3) électriques de son gauche et droit de manière à compenser l'acoustique à l'avant du véhicule, à l'aide d'un module (4.1 ) de correction spectrale.the frequency spectrum of the electric left and right signals (2, 3) is equalized so as to compensate the acoustics at the front of the vehicle by means of a spectral correction module (4.1).
11. Procédé selon l'une des revendications 1 à 10, dans lequel :11. Method according to one of claims 1 to 10, wherein:
- on filtre des bandes de fréquence de chaque signal électrique de son (2bis, 3bis), etfrequency bands of each electrical sound signal are filtered (2a, 3a), and
- on introduit des retards (t1-t4) dans ces bandes de fréquence,delays are introduced (t1-t4) in these frequency bands,
- les retards (t1-t4) étant choisis de manière à aligner temporellement les haut-parleurs du transducteur avant gauche ainsi que les haut-parleurs du transducteur avant droit diffusant ces bandes de fréquence.the delays (t1-t4) being chosen so as to temporally align the speakers of the left front transducer as well as the speakers of the right front transducer diffusing these frequency bands.
12. Procédé selon la revendication 11 , dans lequel :The method of claim 11, wherein:
- on filtre la partie basse fréquence et la partie haute fréquence de chaque signal électrique de son (2bis, 3bis),the low frequency part and the high frequency part of each electrical signal of sound are filtered (2a, 3a),
- les transducteurs (21 , 26) comportant chacun un haut-parleur (22.2, 27.2) basse fréquence et un haut-parleur (22.1 , 27.1 ) haute fréquence,the transducers (21, 26) each comprising a low frequency loudspeaker (22.2, 27.2) and a high frequency loudspeaker (22.1, 27.1),
- les retards (t1 , t3) étant choisis de manière à aligner temporellement les haut-parleurs (22.1 , 22.2) diffusant respectivement les parties basse (5b) et haute (5a) fréquence du signal (20) électrique de son gauche,the delays (t1, t3) being chosen so as to temporally align the loudspeakers (22.1, 22.2) respectively diffusing the low (5b) and high (5a) portions of the electric signal (20) of its left,
- les retards (t2, t4) étant choisis de manière à aligner temporellement les haut-parleurs (27.1 , 27.2) diffusant respectivement les parties basse (6b) et haute (6a) fréquence du signal électrique de son droit (25).the delays (t2, t4) being chosen so as to temporally align the loudspeakers (27.1, 27.2) respectively diffusing the low (6b) and high (6a) portions of the electrical signal of its right (25).
13. Procédé selon la revendication 12, dans lequel :The method of claim 12, wherein:
- les délais gauche et droit (t1 , t2) appliqués sur les haut-parleurs haute fréquence (22.1 , 27.1 ) sont identiques, etthe left and right delays (t1, t2) applied to the high frequency loudspeakers (22.1, 27.1) are identical, and
- les délais (t3, t4) gauche et droit appliqués sur les haut-parleurs basse fréquence (22.2, 27.2) sont identiques. the left and right delays (t3, t4) applied to the low frequency loudspeakers (22.2, 27.2) are identical.
14. Procédé selon l'une des revendications 11 à 13, dans lequel :14. Process according to one of Claims 11 to 13, in which:
- les bandes de fréquence des haut-parleurs (22.1 , 22.2, 27.1 , 27.2) correspondent aux bandes de fréquence des signaux filtrés qu'ils diffusent.- The frequency bands of the loudspeakers (22.1, 22.2, 27.1, 27.2) correspond to the frequency bands of the filtered signals that they broadcast.
15. Procédé selon l'une des revendications 11 à 14, dans lequel :15. Method according to one of claims 11 to 14, wherein:
- les bandes de fréquence du signal (5) électrique de son gauche sont combinées en un signal (20) électrique de son gauche reconstitué, ce signalthe frequency bands of the electric signal (5) of its left are combined into an electrical signal (20) of its reconstituted left, this signal
(20) électrique de son gauche reconstitué étant diffusé par le transducteur(20) Reconstituted left sound electric being diffused by the transducer
(21 ) avant gauche, - les bande de fréquence du signal (6) électrique de son droit sont combinées en un signal (25) électrique de son droit reconstitué, ce signal électrique de son droit reconstitué étant diffusé par le transducteur (26) avant droit.(21) front left, - the frequency band of the electrical signal (6) of its right are combined into an electric signal (25) of its reconstituted right, this electric signal of its reconstituted right being diffused by the transducer (26) before law.
16. Procédé selon l'une des revendications 11 à 15, dans lequel :16. Method according to one of claims 11 to 15, wherein:
- les bandes de fréquence des signaux (5, 6) électriques de son sont ajustées en volume par des cellules de gain (15.1-15.4).the frequency bands of the electric sound signals (5, 6) are adjusted in volume by gain cells (15.1-15.4).
17. Procédé selon l'une des revendications 1 à 16, dans lequel : - on génère un signal (55) électrique de son central à partir des composantes spectrales en phase de signaux (2, 3) électriques de son gauche et droit originaux d'une source (1 ) stéréophonique,17. Method according to one of claims 1 to 16, wherein: - generates an electrical signal (55) of its central from the phase spectral components of electrical signals (2, 3) of its left and right original d a source (1) stereophonic,
- ce signal (55) électrique de son central étant diffusé, après introduction d'un retard (t7), et ajustement en niveau et en volume, par un transducteur (61) positionné au centre du tableau de bord.- This electric signal (55) of its central being diffused, after introduction of a delay (t7), and adjustment in level and volume, by a transducer (61) positioned in the center of the dashboard.
18. Procédé selon la revendication 17, dans lequel :The method of claim 17, wherein:
- le signal (51) électrique de son gauche et le signal (52) électrique de son droit sont obtenus par soustraction des composantes spectrales du signal (55) électrique de son central respectivement à celles du signal (2) électrique de son gauche original et à celles du signal (3) électrique de son droit original.the electric signal (51) of its left and the electric signal (52) of its right are obtained by subtraction of the spectral components of the electrical signal (55) from its central respectively to those of the electric signal (2) of its original left and to those of the electric signal (3) of its original right.
19. Procédé selon l'une des revendications 1 à 18, dans lequel, - on génère des signaux (53, 54) électriques de son gauche et droit arrière, à partir des composantes sensiblement hors phase des signaux (2, 3) électriques de son gauche et droit,19. Method according to one of claims 1 to 18, wherein, electrical signals (53, 54) of its left and right back are generated from the substantially out-of-phase components of the electrical signals (2, 3) of its left and right,
- ces signaux (53, 54) étant diffusés, après introduction d'un retard (t5, t6) et ajustement en niveau et en volume, respectivement par un transducteur (39) arrière gauche et un transducteur (41 ) arrière droit.- these signals (53, 54) being diffused, after introduction of a delay (t5, t6) and adjustment in level and volume, respectively by a left rear transducer (39) and a right rear transducer (41).
20. Procédé selon l'une des revendications 1 à 19, dans lequel,20. Method according to one of claims 1 to 19, wherein,
- on filtre des bandes de fréquence de chaque signal électrique de son (2bis, 3bis), etfrequency bands of each electrical sound signal are filtered (2a, 3a), and
- on introduit des retards (t1-t4) dans ces bandes de fréquence,delays are introduced (t1-t4) in these frequency bands,
- les retards (t1-t4) étant choisis de sorte que les transducteurs diffusant ces bandes de fréquence se situent virtuellement sur un cercle (C), ce cercle (C) ayant pour centre l'endroit où se situe le conducteur et présentant un rayon (RHPmax) dont la distance est celle qui sépare le conducteur du transducteur le plus éloigné du conducteur.the delays (t1-t4) being chosen so that the transducers diffusing these frequency bands lie virtually on a circle (C), this circle (C) having as its center the location where the conductor is located and having a radius (RHPmax) whose distance is that which separates the driver from the transducer furthest away from the driver.
21. Procédé selon la revendication 20, dans lequel :The method of claim 20, wherein:
- on filtre la partie basse fréquence et la partie haute fréquence de chaque signal électrique de son (2bis, 3bis),the low frequency part and the high frequency part of each electrical signal of sound are filtered (2a, 3a),
- les transducteurs (21 , 26) comportant chacun un haut-parleur (22.2, 27.2) basse fréquence situé dans la portière avant et un haut-parleur (22.1 , 27.1) haute fréquence positionné dans le tableau de bord du véhicule,- the transducers (21, 26) each comprising a low frequency loudspeaker (22.2, 27.2) located in the front door and a high frequency loudspeaker (22.1, 27.1) positioned in the vehicle dashboard,
- les retards (t1 , t3) étant choisis de manière à aligner temporellement les haut-parleurs (22.1 , 22.2) diffusant respectivement les parties basse (5b) et haute (5a) fréquence du signal (20) électrique de son gauche,the delays (t1, t3) being chosen so as to temporally align the loudspeakers (22.1, 22.2) respectively diffusing the low (5b) and high (5a) portions of the electric signal (20) of its left,
- les retards (t2, t4) étant choisis de manière à aligner temporellement les haut-parleurs (27.1 , 27.2) diffusant respectivement les parties basse (6b) et haute (6a) fréquence du signal électrique de son droit (25).the delays (t2, t4) being chosen so as to temporally align the loudspeakers (27.1, 27.2) respectively diffusing the low (6b) and high (6a) portions of the electrical signal of its right (25).
22. Procédé selon la revendication 20 ou 21 , dans lequel :22. The method of claim 20 or 21, wherein:
- les délais gauche et droit (t1 , t2) appliqués sur les haut-parleurs haute fréquence (22.1 , 27.1 ) sont identiques, etthe left and right delays (t1, t2) applied to the high frequency loudspeakers (22.1, 27.1) are identical, and
- les délais (t3, t4) gauche et droit appliqués sur les haut-parleurs basse fréquence (22.2, 27.2) sont identiques. the left and right delays (t3, t4) applied to the low frequency loudspeakers (22.2, 27.2) are identical.
23. Véhicule automobile comportant une source (1 ) sonore générant un signal (2, 3) stéréo à l'intérieur d'une voiture,23. Motor vehicle comprising a sound source (1) generating a stereo signal (2, 3) inside a car,
- ce signal stéréo étant composé d'un signal (2) électrique de son gauche et d'un signal (3) électrique de son droit,this stereo signal being composed of an electric signal (2) on its left and an electric signal (3) of its right,
- ces signaux (2, 3) électrique de son gauche et droit étant traités par le procédé selon l'une des revendications 1 à 18 de manière à être diffusés respectivement par un transducteur (21 ) avant gauche comportant uniquement un haut-parleur (22.2) et un transducteur (26) avant droit comportant uniquement un haut-parleur (27.2).these electrical left and right signals (2, 3) being processed by the method according to one of claims 1 to 18 so as to be diffused respectively by a front left transducer (21) comprising only a loudspeaker (22.2); ) and a right front transducer (26) with only one loudspeaker (27.2).
24. Véhicule selon la revendication 23, dans lequel les haut-parleurs (22.2, 27.2) avant gauche et droit sont des haut-parleurs large-bande. 24. Vehicle according to claim 23, wherein the front left and right loudspeakers (22.2, 27.2) are wide-band loudspeakers.
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KR20100054794A (en) 2010-05-25
MY152403A (en) 2014-09-30
WO2009004268A2 (en) 2009-01-08
ATE508593T1 (en) 2011-05-15
FR2918532A1 (en) 2009-01-09
DE602008006725D1 (en) 2011-06-16
FR2918532B1 (en) 2015-04-24
EP2163126B1 (en) 2011-05-04
WO2009004268A3 (en) 2009-02-12
US20100208900A1 (en) 2010-08-19
US8483396B2 (en) 2013-07-09
JP5366943B2 (en) 2013-12-11
JP2010532613A (en) 2010-10-07

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