EP3182723A1 - Audio signal distribution - Google Patents
Audio signal distribution Download PDFInfo
- Publication number
- EP3182723A1 EP3182723A1 EP15200450.3A EP15200450A EP3182723A1 EP 3182723 A1 EP3182723 A1 EP 3182723A1 EP 15200450 A EP15200450 A EP 15200450A EP 3182723 A1 EP3182723 A1 EP 3182723A1
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- EP
- European Patent Office
- Prior art keywords
- loudspeaker
- additional
- headphone
- transfer functions
- audio
- 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.)
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
- H04R1/1083—Reduction of ambient noise
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/175—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound
- G10K11/178—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase
- G10K11/1781—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions
- G10K11/17813—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using interference effects; Masking sound by electro-acoustically regenerating the original acoustic waves in anti-phase characterised by the analysis of input or output signals, e.g. frequency range, modes, transfer functions characterised by the analysis of the acoustic paths, e.g. estimating, calibrating or testing of transfer functions or cross-terms
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
- G10K2210/10—Applications
- G10K2210/12—Rooms, e.g. ANC inside a room, office, concert hall or automobile cabin
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
- G10K2210/10—Applications
- G10K2210/128—Vehicles
- G10K2210/1282—Automobiles
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K2210/00—Details of active noise control [ANC] covered by G10K11/178 but not provided for in any of its subgroups
- G10K2210/30—Means
- G10K2210/301—Computational
- G10K2210/3055—Transfer function of the acoustic system
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2460/00—Details of hearing devices, i.e. of ear- or headphones covered by H04R1/10 or H04R5/033 but not provided for in any of their subgroups, or of hearing aids covered by H04R25/00 but not provided for in any of its subgroups
- H04R2460/01—Hearing devices using active noise cancellation
Definitions
- the disclosure relates to a system and method (generally referred to as a "system") for distributing an audio signal.
- system a system and method for distributing an audio signal.
- Headphone listening is becoming increasingly popular due to the propagation of portable audio players. Even mobile phones now also allow music playback over headphones. Headphones are also increasingly used in rear-seat entertainment systems to allow people sitting in the back of the car to listen to music or watch videos without being disturbed by audio content being played on the main car audio installation, and without disturbing the front passengers.
- ANC active noise control
- Another trend is the growing use of active noise control (ANC) headphones which isolate the user from the ambient sound such as car engine noise, fan noise or audio content played on the main car audio installation by means of anti-sound played through the headphone speakers.
- the anti-sound is calculated from sound picked up by microphones placed on or in the headphone. However, the ambient noise may be insufficiently picked up by the microphones so that the noise control performance of the whole system deteriorates.
- An audio signal distribution system is configured to receive an audio source signal to be reproduced by a loudspeaker disposed at a first position, to provide to the loudspeaker a loudspeaker signal that represents the audio source signal to be reproduced by the loudspeaker, and to provide to two speakers of a headphone, disposed at a second position and a third position, two headphone signals which comprise the loudspeaker signals filtered with electrical domain transfer functions.
- the electrical domain transfer functions are configured to model acoustic domain transfer functions representing the acoustic paths between the first position and each of the second position and third position so that at the second position and third position sound acoustically broadcasted by the loudspeaker is reduced or cancelled by sound broadcasted by the respective speaker.
- An audio signal distribution method comprises receiving an audio source signal to be reproduced by a loudspeaker disposed at a first position, and providing to the loudspeaker a loudspeaker signal that represents the audio source signal to be reproduced by the loudspeaker.
- the method further comprises providing to two speakers of a headphone, disposed at a second position and a third position, two headphone signals which comprise the loudspeaker signals filtered with electrical domain transfer functions.
- the electrical domain transfer functions are configured to model acoustic domain transfer functions representing the acoustic paths between the first position and each of the second position and third position so that at the second position and third position sound acoustically broadcasted by the loudspeaker is reduced or cancelled by sound broadcasted by the respective speaker of the headphone.
- a program code of processing audio data when being executed by a processor, is configured to carry out or control the method described above.
- two different stereophonic audio contents such as, for example, two different pieces of music are to be reproduced at two different positions 101 and 102 in the interior of an automobile 103 (or any other room).
- Position 101 may be the front left seat position and position 102 may be the rear right seat position in the interior of automobile 103.
- the content intended to be played at position 101 is reproduced by way of two loudspeakers 104 and 105 arranged in front and to the left and right of position 101, and the content intended to be played at position 102 is reproduced by way of a headphone 106 with two headphone speakers 107 and 108.
- loudspeakers 109 and 110 disposed on the rear shelf of automobile 103 may be employed but for the sake of simplicity only loudspeakers 104 and 105 are looked at more closely in the following description.
- the behavior of loudspeakers 109 and 110 with regard to a user (listener) sitting at position 102 can be described in a similar manner to that of loudspeakers 104 and 105.
- Figure 2 illustrates electrical and acoustic paths present in the audio arrangement shown in Figure 1 , in which binaural (stereo) signals are picked up by the left ear 201 and the right ear 202 of a user 203 sitting at position 102.
- the signals broadcasted by loudspeakers 104 and 105 may be input electrical stereo audio signals X L (j ⁇ ) and X R (j ⁇ ) which represent a first audio content to be audible at position 101 but not at position 102.
- the signals X L (j ⁇ ) and X R (j ⁇ ) are frequency domain signals that correspond with time domain signals.
- Filters 204 and 206 filter signal X L (j ⁇ ) with transfer functions C LL (j ⁇ ) and C LR (j ⁇ ), respectively, and filters 205 and 207 filter signal X R (j ⁇ ) with transfer functions C RR (j ⁇ ) and C RL (j ⁇ ), respectively, to provide inverse filter output signals.
- the filter output signals provided by filters 204 and 206 are combined by an adder 208 and inverse filter output signals provided by filters 205 and 207 are combined by an adder 209 to form combined signals S L (j ⁇ ) and S R (j ⁇ ).
- the headphone speakers 107 and 108 radiate the combined signals S L (j ⁇ ) and S R (j ⁇ ) to the left ear 201 and right ear 202 of the user 203 with transfer functions which are neglected in the following considerations due to their minor significance.
- the loudspeakers 104 and 105 receive the input electrical stereo audio signals X L (j ⁇ ) and X R (j ⁇ ) and convert them into sound signals which are transferred via respective acoustic paths with transfer functions Hij(j ⁇ ) to the left ear 201 and right ear 202 of the user 203.
- the transfer functions Hij(j ⁇ ) denote the room impulse response (RIR) in the frequency domain, i.e. the transfer functions from the loudspeakers 104 and 105 to the left ear 201 and right ear 202 of the user 203.
- Index i is “L” when it refers to the left loudspeaker 104 and “R” when it refers to the right loudspeaker 105.
- Index j is “L” when it refers to the left ear 201 and “R” when it refers to the right ear 202.
- the automotive multimedia entertainment system includes an audio system 301, the headphone 106, a two-way wired (alternatively: wireless) communication link 302, a set of front speakers including the loudspeakers 104 and 105, and a set of rear speakers (not shown in Figure 3 ).
- the audio system 301 can receive audio input signals from multiple audio input devices, for example a CD player 303, a cassette player 304, a radio tuner 305, a DVD player 306, and other auxiliary devices 307.
- the audio input signals are received by a multiplexer 308 of the audio system 301 and selected in accordance with two selection signals from program switches 316 and 317 to provide two different audio contents, a first audio content and a second audio content.
- the multiplexer 308 can provide each of the two audio contents from any of the audio input devices 303-307 across a stereo channel 309 transmitting the first audio content to be reproduced by loudspeakers 104 and 105 and across a stereo channel 310 transmitting the second audio content to be reproduced by the headphone 106 to an audio processor 315.
- the audio processor 315 may, for example, be operated to perform the functions of the filters 204-207 and the adders 208, 209 described above in connection with Figure 2 in which audio signals X L (j ⁇ ) and X R (j ⁇ ) represent the first audio content to be audible at position 101 and reproduced by loudspeakers 104 and 105, and signals Y L (j ⁇ ) and Y R (j ⁇ ) represent the second audio content to be audible at position 102 and reproduced by headphone 106.
- the signals X L (j ⁇ ) and X R (j ⁇ ) and the signals Y L (j ⁇ ) and Y R (j ⁇ ) can be attenuated by way of attenuators 318 and 319.
- Amplifiers 311 and 312 are connected downstream of the audio processor 315 and upstream of the loudspeakers 104 and 105.
- Amplifiers 313 and 314 are connected downstream of the audio processor 315 and upstream of the headphone 106.
- the attenuator 318 allows, for example, the front seat passenger to control the volume of the signals X L (j ⁇ ) and X R (j ⁇ ) and may be mounted in the instrument panel or integrated into the steering wheel together with the program switch 316.
- the attenuator 319 allows, for example, the user wearing the headphone 106 to control the volume of the signals Y L (j ⁇ ) and Y R (j ⁇ ) and may be mounted in the arm rest of the rear seats which may also house the program switch 317 and a connector jacket for the headphone in case of a wired connection 302.
- the audio system including the multiplexer 308 and the audio processor 315, may be in the form of an embedded system and controlled by software.
- a transceiver 401 may be included in the audio system 301 as shown in Figure 4 .
- the transceiver 401 is adapted to establish a two-way wireless communication link 402 with a transceiver 403 connected to the headphone 106.
- Transceivers 401 and 403 may be implemented using infrared or radio frequency transceivers, e.g., according to a Bluetooth® or near field communication (NFC) standard.
- Transceiver 403 and/or a set of controls may be integrated in the headphone106 for configuring program and audio parameters associated with, e.g., audio channel 310 shown in Figure 3 .
- a power "on” control 404 may be integrated into the headphone 106. When the power "on” control is activated and the headphone is switched on, this may be reported to the audio system 301 which then deactivates the rear speakers and connects audio channel 310 to the headphone 106. A similar mechanism may be used with wired connection 302 when it is detected that the headphone is connected by wire to the audio system 301.
- a head tracking system 501 may be included in the audio system shown in Figure 2 to determine a rotation angle of the head of the user 203 wearing the headphone 106 with respect to a reference direction (e.g., the direction to the front of the car), which may also be dependent on a movement of the user 203.
- a reference direction e.g., the direction to the front of the car
- the movement of a user should be understood as an act or process of moving including e.g. changes of position or posture, such as leaning back or settling into the seat.
- the head tracking system 501 may include a sensing device (not shown), such as an array of video cameras, for measuring a head movement to provide a measurement representing the head movement, and a processing circuit (not shown) for deriving the rotation angle of the head of the user with respect to the reference direction from the measurement.
- the reference direction used in the processing circuit may be fixed or dependent on the linear movement of the user.
- a multitude of other (known) head tracking systems (mainly consumer headphone or gaming applications) may be employed which use e.g. ultrasonic technology, infrared technology, transmitters/receivers, gyroscopes, or multiple sensors.
- these head tracking systems may determine the head position relative to an environment, either by using a fixed reference with a stable (invariant) position relative to the environment (e.g. an infrared 'beacon, or using the earth magnetic field), or by using sensor technology that, once calibrated, does not drift significantly during the listening session (e.g. by using high-accuracy gyroscopes).
- a fixed reference with a stable (invariant) position relative to the environment
- sensor technology e.g. an infrared 'beacon, or using the earth magnetic field
- Other implementations may include one or more cameras whose video signals are evaluated with adequate software.
- the determined position and the rotation angle of the head 203 of the user wearing headphone 106 is used to control the transfer functions of filters 204-207. All possible (discrete) positions of the head 203 are associated with specific transfer functions H' LL (j ⁇ ), H' RL (j ⁇ ), H' LR (j ⁇ ) and H' RR (j ⁇ ) that vary with the head position.
- the adjustments may be made, for example, by way of look-up tables which provide for each (discrete) position detected by the head tracking system 501 the transfer functions C' LL (j ⁇ ), C' RL (j ⁇ ), C' LR (j ⁇ ) and C' RR (j ⁇ ).
- the transfer functions C' LL (j ⁇ ), C' RL (j ⁇ ), C' LR (j ⁇ ) and C' RR (j ⁇ ) correspond to the actual transfer functions H' LL (j ⁇ ), H' RL (j ⁇ ), H' LR (j ⁇ ) and H' RR (j ⁇ ).
- the transfer functions C' LL (j ⁇ ), C' RL (j ⁇ ), C' LR (j ⁇ ) and C' RR (j ⁇ ) may be calculated from the detected positions using models or equation systems.
- an exemplary audio signal distribution method may include receiving audio source signals to be reproduced by loudspeakers disposed at a first and fourth position (procedure 601), providing to the loudspeakers loudspeaker signals that represent the audio content to be reproduced by the loudspeakers (procedure 602), and providing to two speakers of a headphone, disposed at a second position and a third position, two headphone signals (procedure 603).
- the headphone signals comprise the loudspeaker signals filtered with electrical domain transfer functions (procedure 604).
- the electrical domain transfer functions may be configured to model acoustic domain transfer functions representing the acoustic paths between each of the first and fourth position and each of the second and third position so that at the second position and third position sound acoustically broadcasted by the loudspeakers is reduced or cancelled by sound broadcasted by the respective speaker of the headphone.
- the audio signal distribution method may further include receiving two audio source signals to be reproduced by the headphone (procedure 605). The two audio source signals to be reproduced by the headphone are combined with the loudspeaker signals filtered with electrical domain transfer functions to form the two headphone signals (procedure 606).
- At least one additional audio source signal to be reproduced by at least one additional loudspeaker disposed at additional positions may be received (procedure 606) and at least one additional loudspeaker signal that represents the at least one additional audio source signal to be reproduced by the at least one additional loudspeaker may be provided to the at least one additional loudspeaker.
- the two headphone signals provided to the two speakers may further comprise the at least one additional loudspeaker signal filtered with additional electrical domain transfer functions, in which the additional electrical domain transfer functions may be configured to model acoustic domain transfer functions representing the acoustic paths between each additional position and each of the second position and third position so that at the second position and third position sound acoustically broadcasted by the at least one additional loudspeaker is reduced or cancelled by sound broadcasted by the related speaker.
- the position(s) of the loudspeaker(s), the positions of the speakers of the headphone (and maybe additional positions) are spatially constant and the related electrical domain transfer functions are timely constant.
- the method may further include receiving a headtracking signal indicative of the actual speaker positions (procedure 607), and, if the first position positions of the loudspeaker(s) are spatially constant and the positions of the speakers of the headphone are spatially variable, controlling the related electrical domain transfer functions according to the actual speaker positions (procedure 608).
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Abstract
Description
- The disclosure relates to a system and method (generally referred to as a "system") for distributing an audio signal.
- Headphone listening is becoming increasingly popular due to the propagation of portable audio players. Even mobile phones now also allow music playback over headphones. Headphones are also increasingly used in rear-seat entertainment systems to allow people sitting in the back of the car to listen to music or watch videos without being disturbed by audio content being played on the main car audio installation, and without disturbing the front passengers. Another trend is the growing use of active noise control (ANC) headphones which isolate the user from the ambient sound such as car engine noise, fan noise or audio content played on the main car audio installation by means of anti-sound played through the headphone speakers. The anti-sound is calculated from sound picked up by microphones placed on or in the headphone. However, the ambient noise may be insufficiently picked up by the microphones so that the noise control performance of the whole system deteriorates.
- An audio signal distribution system is configured to receive an audio source signal to be reproduced by a loudspeaker disposed at a first position, to provide to the loudspeaker a loudspeaker signal that represents the audio source signal to be reproduced by the loudspeaker, and to provide to two speakers of a headphone, disposed at a second position and a third position, two headphone signals which comprise the loudspeaker signals filtered with electrical domain transfer functions. The electrical domain transfer functions are configured to model acoustic domain transfer functions representing the acoustic paths between the first position and each of the second position and third position so that at the second position and third position sound acoustically broadcasted by the loudspeaker is reduced or cancelled by sound broadcasted by the respective speaker.
- An audio signal distribution method comprises receiving an audio source signal to be reproduced by a loudspeaker disposed at a first position, and providing to the loudspeaker a loudspeaker signal that represents the audio source signal to be reproduced by the loudspeaker. The method further comprises providing to two speakers of a headphone, disposed at a second position and a third position, two headphone signals which comprise the loudspeaker signals filtered with electrical domain transfer functions. The electrical domain transfer functions are configured to model acoustic domain transfer functions representing the acoustic paths between the first position and each of the second position and third position so that at the second position and third position sound acoustically broadcasted by the loudspeaker is reduced or cancelled by sound broadcasted by the respective speaker of the headphone.
- A program code of processing audio data, when being executed by a processor, is configured to carry out or control the method described above.
- Other systems, methods, features and advantages will be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims.
- The system may be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views.
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Figure 1 is a block diagram of an exemplary arrangement of loudspeakers and headphone in connection with an in-car entertainment system. -
Figure 2 is a signal flow diagram of an audio signal distribution used in the arrangement shown inFigure 1 . -
Figure 3 is a block diagram illustrating an exemplary in-car multimedia entertainment system. -
Figure 4 is a block diagram illustrating a wireless headphone connection. -
Figure 5 is a signal flow diagram illustrating the arrangement shown inFigure 1 , which additionally employs headtracking. -
Figure 6 is a process chart illustrating an exemplary audio signal distribution method. - In an exemplary audio arrangement shown in
Figure 1 , two different stereophonic audio contents such as, for example, two different pieces of music are to be reproduced at twodifferent positions Position 101 may be the front left seat position andposition 102 may be the rear right seat position in the interior ofautomobile 103. The content intended to be played atposition 101 is reproduced by way of twoloudspeakers position 101, and the content intended to be played atposition 102 is reproduced by way of aheadphone 106 with twoheadphone speakers headphone speakers position 101, particularly whenloudspeakers loudspeakers position 102 even when a user wears theheadphone 106. Further loudspeakers such as, for example,loudspeakers automobile 103 may be employed but for the sake of simplicity onlyloudspeakers loudspeakers position 102 can be described in a similar manner to that ofloudspeakers -
Figure 2 illustrates electrical and acoustic paths present in the audio arrangement shown inFigure 1 , in which binaural (stereo) signals are picked up by theleft ear 201 and theright ear 202 of auser 203 sitting atposition 102. The signals broadcasted byloudspeakers position 101 but not atposition 102. For illustration purposes, the signals XL(jω) and XR(jω) are frequency domain signals that correspond with time domain signals. The left electrical input (audio) signal XL(jω) and the right electrical input (audio) signal XR(jω), which may be provided by any suitable audio signal source such as a radio receiver, music player, telephone, navigation system or the like, are, on one hand, supplied to theloudspeakers headphone speakers Filters filters adder 208 and inverse filter output signals provided byfilters adder 209 to form combined signals SL(jω) and SR(jω). In particular, signal SL(jω) supplied to theleft headphone speaker 107 can be expressed as:right headphone speaker 108 can be expressed as: - The
headphone speakers left ear 201 andright ear 202 of theuser 203 with transfer functions which are neglected in the following considerations due to their minor significance. Theloudspeakers left ear 201 andright ear 202 of theuser 203. The sound signal present at theleft ear 201 andright ear 202 is denoted as ZL(jω) and ZR(jω), in which - In equations 3 and 4, the transfer functions Hij(jω) denote the room impulse response (RIR) in the frequency domain, i.e. the transfer functions from the
loudspeakers left ear 201 andright ear 202 of theuser 203. Index i is "L" when it refers to theleft loudspeaker 104 and "R" when it refers to theright loudspeaker 105. Index j is "L" when it refers to theleft ear 201 and "R" when it refers to theright ear 202. - Inserting equations 1 and 2 into equations 3 and 4 leads to equations 5 and 6:
loudspeakers user 203 who wears theheadphone 106. When adding signals YL(jω) and YR(jω), which represent another audio content, to signals SL(jω) and SR(jω), the resulting sum signals YL(jω)+SL(jω) and YR(jω)+SR(jω) interfere, after being radiated byheadphone speakers user 203. - An in-car multimedia entertainment system used in the arrangement described above in connection with
Figures 1 and2 is shown inFigure 3 . As its primary components, the automotive multimedia entertainment system includes anaudio system 301, theheadphone 106, a two-way wired (alternatively: wireless)communication link 302, a set of front speakers including theloudspeakers Figure 3 ). Theaudio system 301 can receive audio input signals from multiple audio input devices, for example aCD player 303, acassette player 304, aradio tuner 305, aDVD player 306, and otherauxiliary devices 307. The audio input signals are received by amultiplexer 308 of theaudio system 301 and selected in accordance with two selection signals fromprogram switches multiplexer 308 can provide each of the two audio contents from any of the audio input devices 303-307 across astereo channel 309 transmitting the first audio content to be reproduced byloudspeakers stereo channel 310 transmitting the second audio content to be reproduced by theheadphone 106 to anaudio processor 315. Theaudio processor 315 may, for example, be operated to perform the functions of the filters 204-207 and theadders Figure 2 in which audio signals XL(jω) and XR(jω) represent the first audio content to be audible atposition 101 and reproduced byloudspeakers position 102 and reproduced byheadphone 106. - The signals XL(jω) and XR(jω) and the signals YL(jω) and YR(jω) can be attenuated by way of
attenuators Amplifiers audio processor 315 and upstream of theloudspeakers Amplifiers audio processor 315 and upstream of theheadphone 106. Theattenuator 318 allows, for example, the front seat passenger to control the volume of the signals XL(jω) and XR(jω) and may be mounted in the instrument panel or integrated into the steering wheel together with theprogram switch 316. Theattenuator 319 allows, for example, the user wearing theheadphone 106 to control the volume of the signals YL(jω) and YR(jω) and may be mounted in the arm rest of the rear seats which may also house theprogram switch 317 and a connector jacket for the headphone in case of awired connection 302. The audio system, including themultiplexer 308 and theaudio processor 315, may be in the form of an embedded system and controlled by software. - If a
wireless connection 402 is used instead ofwired connection 302, atransceiver 401 may be included in theaudio system 301 as shown inFigure 4 . Thetransceiver 401 is adapted to establish a two-waywireless communication link 402 with atransceiver 403 connected to theheadphone 106.Transceivers Transceiver 403 and/or a set of controls (not shown) may be integrated in the headphone106 for configuring program and audio parameters associated with, e.g.,audio channel 310 shown inFigure 3 . A power "on" control 404 may be integrated into theheadphone 106. When the power "on" control is activated and the headphone is switched on, this may be reported to theaudio system 301 which then deactivates the rear speakers and connectsaudio channel 310 to theheadphone 106. A similar mechanism may be used withwired connection 302 when it is detected that the headphone is connected by wire to theaudio system 301. - Referring now to
Figure 5 , ahead tracking system 501 may be included in the audio system shown inFigure 2 to determine a rotation angle of the head of theuser 203 wearing theheadphone 106 with respect to a reference direction (e.g., the direction to the front of the car), which may also be dependent on a movement of theuser 203. Here the movement of a user should be understood as an act or process of moving including e.g. changes of position or posture, such as leaning back or settling into the seat. Thehead tracking system 501 may include a sensing device (not shown), such as an array of video cameras, for measuring a head movement to provide a measurement representing the head movement, and a processing circuit (not shown) for deriving the rotation angle of the head of the user with respect to the reference direction from the measurement. The reference direction used in the processing circuit may be fixed or dependent on the linear movement of the user. Alternatively, a multitude of other (known) head tracking systems (mainly consumer headphone or gaming applications) may be employed which use e.g. ultrasonic technology, infrared technology, transmitters/receivers, gyroscopes, or multiple sensors. For example, these head tracking systems may determine the head position relative to an environment, either by using a fixed reference with a stable (invariant) position relative to the environment (e.g. an infrared 'beacon, or using the earth magnetic field), or by using sensor technology that, once calibrated, does not drift significantly during the listening session (e.g. by using high-accuracy gyroscopes). Other implementations may include one or more cameras whose video signals are evaluated with adequate software. - The determined position and the rotation angle of the
head 203 of theuser wearing headphone 106 is used to control the transfer functions of filters 204-207. All possible (discrete) positions of thehead 203 are associated with specific transfer functions H'LL(jω), H'RL(jω), H'LR(jω) and H'RR(jω) that vary with the head position. When adjusting variable transfer functions C'LL(jω), C'RL(jω), C'LR(jω) and C'RR(jω) of the filters 204-207 so that for each particular position the transfer functions C'LL(jω), C'RL(jω), C'LR(jω) and C'RR(jω) are the inverse of the transfer functions H'LL(jω), H'RL(jω), H'LR(jω) and H'RR(jω), the situation outlined above in connection withFigure 2 is true for every possible head position. The adjustments may be made, for example, by way of look-up tables which provide for each (discrete) position detected by thehead tracking system 501 the transfer functions C'LL(jω), C'RL(jω), C'LR(jω) and C'RR(jω). The transfer functions C'LL(jω), C'RL(jω), C'LR(jω) and C'RR(jω) correspond to the actual transfer functions H'LL(jω), H'RL(jω), H'LR(jω) and H'RR(jω). Alternatively, the transfer functions C'LL(jω), C'RL(jω), C'LR(jω) and C'RR(jω) may be calculated from the detected positions using models or equation systems. - Referring to
Figure 6 , an exemplary audio signal distribution method may include receiving audio source signals to be reproduced by loudspeakers disposed at a first and fourth position (procedure 601), providing to the loudspeakers loudspeaker signals that represent the audio content to be reproduced by the loudspeakers (procedure 602), and providing to two speakers of a headphone, disposed at a second position and a third position, two headphone signals (procedure 603). The headphone signals comprise the loudspeaker signals filtered with electrical domain transfer functions (procedure 604). The electrical domain transfer functions may be configured to model acoustic domain transfer functions representing the acoustic paths between each of the first and fourth position and each of the second and third position so that at the second position and third position sound acoustically broadcasted by the loudspeakers is reduced or cancelled by sound broadcasted by the respective speaker of the headphone. The audio signal distribution method may further include receiving two audio source signals to be reproduced by the headphone (procedure 605). The two audio source signals to be reproduced by the headphone are combined with the loudspeaker signals filtered with electrical domain transfer functions to form the two headphone signals (procedure 606). - At least one additional audio source signal to be reproduced by at least one additional loudspeaker disposed at additional positions may be received (procedure 606) and at least one additional loudspeaker signal that represents the at least one additional audio source signal to be reproduced by the at least one additional loudspeaker may be provided to the at least one additional loudspeaker. The two headphone signals provided to the two speakers may further comprise the at least one additional loudspeaker signal filtered with additional electrical domain transfer functions, in which the additional electrical domain transfer functions may be configured to model acoustic domain transfer functions representing the acoustic paths between each additional position and each of the second position and third position so that at the second position and third position sound acoustically broadcasted by the at least one additional loudspeaker is reduced or cancelled by sound broadcasted by the related speaker. The position(s) of the loudspeaker(s), the positions of the speakers of the headphone (and maybe additional positions) are spatially constant and the related electrical domain transfer functions are timely constant. The method may further include receiving a headtracking signal indicative of the actual speaker positions (procedure 607), and, if the first position positions of the loudspeaker(s) are spatially constant and the positions of the speakers of the headphone are spatially variable, controlling the related electrical domain transfer functions according to the actual speaker positions (procedure 608).
- While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.
Claims (15)
- An audio signal distribution system configured to:receive an audio source signal to be reproduced by a loudspeaker disposed at a first position;provide to the loudspeaker a loudspeaker signal that represents the audio source signal to be reproduced by the loudspeaker; andprovide to two speakers of a headphone, disposed at a second position and a third position, two headphone signals which comprise the loudspeaker signals filtered with electrical domain transfer functions, the electrical domain transfer functions configured to model acoustic domain transfer functions representing the acoustic paths between the first position and each of the second position and third position so that at the second position and third position sound acoustically broadcasted by the loudspeaker is reduced or cancelled by sound broadcasted by the respective speaker.
- The audio signal distribution system of claim 1, further configured to receive at least one audio source signal to be reproduced by the headphone, the at least one audio source signal to be reproduced by the headphone is combined with the loudspeaker signals filtered with electrical domain transfer functions to form the two headphone signals.
- The audio signal distribution system of claim 1or 2, further configured to:receive at least one additional audio source signal to be reproduced by at least one additional loudspeaker disposed at additional positions; andprovide to the at least one additional loudspeaker at least one additional loudspeaker signal that represents the at least one additional audio source signal to be reproduced by the at least one additional loudspeaker; whereinthe two headphone signals provided to the two speakers further comprise the at least one additional loudspeaker signal filtered with additional electrical domain transfer functions, the additional electrical domain transfer functions configured to model acoustic domain transfer functions representing the acoustic paths between each additional position and each of the second position and third position so that at the second position and third position sound acoustically broadcasted by the at least one additional loudspeaker is reduced or cancelled by sound broadcasted by the related speaker.
- The audio signal distribution system of any of claims 1to 3, further configured to provide a wireless connection to the headphone.
- The audio signal distribution system of any of claims 1to 4, wherein the first position, the second position and the third position and/or the additional positions are spatially constant and the related electrical domain transfer functions are timely constant.
- The audio signal distribution system of any of claims 1to 4, further configured to receive a headtracking signal indicative of the actual speaker positions, wherein the first position and/or the additional positions are spatially constant, the second position and the third position are spatially variable, and the system is further configured to control the related electrical domain transfer functions according to the actual speaker positions.
- The audio signal distribution system of any of claims 1to 6, further comprising at least one additional loudspeaker that is switched off when the headphone is in use.
- An audio signal distribution method comprising:receiving an audio source signal to be reproduced by a loudspeaker disposed at a first position;providing to the loudspeaker a loudspeaker signal that represents the audio source signal to be reproduced by the loudspeaker; andproviding to two speakers of a headphone, disposed at a second position and a third position, two headphone signals which comprise the loudspeaker signals filtered with electrical domain transfer functions, the electrical domain transfer functions configured to model acoustic domain transfer functions representing the acoustic paths between the first position and each of the second position and third position so that at the second position and third position sound acoustically broadcasted by the loudspeaker is reduced or cancelled by sound broadcasted by the respective speaker of the headphone.
- The audio signal distribution method of claim 8, further comprising: receiving at least one audio source signal to be reproduced by the headphone, the at least one audio source signal to be reproduced by the headphone is combined with the loudspeaker signals filtered with electrical domain transfer functions to form the two headphone signals.
- The audio signal distribution method of claim 8 or 9, further comprising:receiving at least one additional audio source signal to be reproduced by at least one additional loudspeaker disposed at additional positions; andproviding to the at least one additional loudspeaker at least one additional loudspeaker signal that represents the at least one additional audio source signal to be reproduced by the at least one additional loudspeaker; whereinthe two headphone signals provided to the two speakers further comprise the at least one additional loudspeaker signal filtered with additional electrical domain transfer functions, the additional electrical domain transfer functions configured to model acoustic domain transfer functions representing the acoustic paths between each additional position and each of the second position and third position so that at the second position and third position sound acoustically broadcasted by the at least one additional loudspeaker is reduced or cancelled by sound broadcasted by the related speaker.
- The audio signal distribution method of any of claims 8 to 10, further comprising: providing a wireless connection to the headphone.
- The audio signal distribution method of any of claims 8 to 11, wherein the first position, the second position and the third position and/or the additional positions are spatially constant and the related electrical domain transfer functions are timely constant.
- The audio signal distribution method of any of claims 8 to 12, further comprising: receiving a headtracking signal indicative of the actual speaker positions, wherein the first position and/or the additional positions are spatially constant, the second position and the third position are spatially variable, and the method further comprises:controlling the related electrical domain transfer functions according to the actual speaker positions.
- The audio signal distribution method of any of claims 8 to 13, further comprising switching off at least one further loudspeaker when the headphone is in use.
- A program code of processing audio data, which program code, when being executed by a processor, is configured to carry out or control a method according to any of claims 8 to 14.
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EP15200450.3A EP3182723A1 (en) | 2015-12-16 | 2015-12-16 | Audio signal distribution |
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EP15200450.3A EP3182723A1 (en) | 2015-12-16 | 2015-12-16 | Audio signal distribution |
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EP2405670A1 (en) * | 2010-07-08 | 2012-01-11 | Harman Becker Automotive Systems GmbH | Vehicle audio system with headrest incorporated loudspeakers |
US20120128166A1 (en) * | 2010-10-25 | 2012-05-24 | Qualcomm Incorporated | Systems, methods, apparatus, and computer-readable media for head tracking based on recorded sound signals |
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US20070242834A1 (en) * | 2001-10-30 | 2007-10-18 | Coutinho Roy S | Noise cancellation for wireless audio distribution system |
US20050032500A1 (en) * | 2003-08-08 | 2005-02-10 | Visteon Global Technologies, Inc. | Wireless/IR headphones with integrated rear seat audio control for automotive entertainment system |
US20110150233A1 (en) * | 2009-12-18 | 2011-06-23 | Nxp B.V. | Device for and a method of processing a signal |
EP2405670A1 (en) * | 2010-07-08 | 2012-01-11 | Harman Becker Automotive Systems GmbH | Vehicle audio system with headrest incorporated loudspeakers |
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