Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S1/00—Two-channel systems
  • H04S1/002—Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
  • H04R3/00—Circuits for transducers, loudspeakers or microphones
  • H04R3/04—Circuits for transducers, loudspeakers or microphones for correcting frequency response
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04S—STEREOPHONIC SYSTEMS 
  • H04S2420/00—Techniques used stereophonic systems covered by H04S but not provided for in its groups
  • H04S2420/01—Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]
• • 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

Definitions

• the invention relates to the general field of acoustic processing and spatialization of sounds.
• It relates more particularly to a method of sound reproduction based on a transaural technique.
• the invention applies for example in a restricted space, such as for example in a passenger compartment of a car or of another vehicle (eg an airplane) equipped with at least two pairs of loudspeakers, in order to reproduce a wide stereophonic sound scene (ie spatialized) around two known listening positions to which listeners are likely to find themselves.
• a restricted space such as for example in a passenger compartment of a car or of another vehicle (eg an airplane) equipped with at least two pairs of loudspeakers, in order to reproduce a wide stereophonic sound scene (ie spatialized) around two known listening positions to which listeners are likely to find themselves.
• these two positions are for example the position of the driver of the car and that of his passenger.
• the invention is however not limited to this single application, and can easily be applied to other sound environments having a similar speaker configuration and in which two different listening positions are aimed.
• Transaural techniques aim to adapt binaural synthesis to a speaker device.
• CTCs cross-cycle cancellation techniques
• echo cancellation In other words, the sound signal emitted by the right speaker on the left ear, and the sound signal emitted by the left speaker on the right ear are eliminated or at least reduced by an appropriate signal processing.
• FIG. 1 illustrates the system envisaged in D1: N sound programs (ie, N multichannel sound signals) are used to generate M signals supplying respectively M loudspeakers of a playback system intended for L / 2 listeners (in other words, L human ears).
• the processing for generating the M power signals of the loudspeakers from the N sound programs is a cross-path cancellation process.
• This system can be modeled in matrix form. So, if:
• Z denotes the acoustic transfer matrix between the N original sound programs and the L signals received respectively by the listeners' ears
• Y denotes the CTC processing matrix between the N original sound programs and the M feed signals of the M loudspeakers (Y represents the transaural filters), and
• X denotes the acoustic propagation matrix between the loudspeakers M and the ears of the listeners
• the matrices X and Z are known: in fact, the matrix Z characterizes the desired sound reproduction at the level of the listeners while the matrix X is measurable. We therefore seek a processing matrix Y satisfying equation (1).
• the matrix X is of dimensions LxM: it is not necessarily square. Moreover, this matrix is not always well conditioned. It is not always invertible. Under such conditions, it is customary to use the pseudo-inverse matrix of the X matrix, denoted by X + , and defined by:
• D1 The technique proposed in D1 is general and is theoretically suitable for any values of N, M and L.
• the invention responds in particular to this need by proposing a method of generating power supply signals intended for a sound reproduction system comprising two sets of loudspeakers situated on either side of a separation plane, these signaling signals.
• power supply being generated for sound reproduction of a multichannel sound signal to two spatial listening positions, each listening space position being associated with one of the speaker sets and being located on a parallel plane to the separation plane so that at least one loudspeaker of this set is positioned on either side of this parallel plane
• the generation method comprising, for each set of loudspeakers, a generating step, to from an input signal derived from the multichannel sound signal for this set, supply signals for supplying the loudspeakers of this set, this generation step comprising the applicati one of a technique of transaural restitution to the input signal, this technique creating a virtual sound source for the listening position associated with the set on a first line obtained by symmetry, with respect to the parallel plane on which is located the listening space position associated with this set of a second straight connecting the listening space position
• the invention also relates to a device for generating supply signals intended for a sound reproduction system comprising two sets of loudspeakers located on either side of a separation plane, said signals being generated for a sound reproduction of a multichannel sound signal to two spatial listening positions, each listening spatial position being associated with one of the speaker sets and being located on a plane parallel to the separation plane so that at least one loudspeaker of this set is positioned on either side of this parallel plane,
• this generation device comprising means able to generate for each set of loudspeakers, from a signal of input derived from the multichannel sound signal for this set, power signals for supplying the speakers of this set, these means being able to apply a technique of restitution tr ansaural to the input signal, this technique creating a virtual sound source for the listening position associated with the set on a first straight line obtained by symmetry, with respect to the parallel plane on which is located the listening spatial position associated with this set of a second straight connecting the listening space position to the speaker more distant from this position belonging to the
• each listening position is in the frontal area of the speakers of the set with which it is associated.
• the invention allows spatialized sound reproduction of a multichannel sound signal, from a speaker array comprising at least two sets of loudspeakers, and simultaneously for two listening positions defined respectively with respect to these two sets of speakers.
• These listening positions are not necessarily punctual: they may indeed be actual listening zones, in which case the listening position on a plane parallel to the separation plane means that the geometric center of this listening position is on the parallel plane.
• These listening spatial zones are preferentially defined by a radius around the geometric center of less than 15-20 cm.
• Each set of speakers of the reproduction system envisaged for the sound reproduction of the multichannel signal thus comprises a loudspeaker on either side of the parallel plane on which the listening position is located.
• the listening position is for example centered with respect to the set of speakers to which it is attached.
• the invention advantageously proposes to treat separately each set of speakers and the listening position attached thereto.
• a separate transaural technique is used for each set of speakers to generate the speaker power signals of this set.
• This transaural technique is implemented according to the invention, so as to create a virtual source outside the speaker array, in the opposite direction with respect to the listening position associated with the set of loudspeakers. considered, to the speaker of the network farthest from this position (and belonging to the other set of speakers).
• the invention combines, on the one hand, the advantages of a transaural reproduction applied to a small number of loudspeakers (resulting from the separate treatment performed on each set of loudspeakers), and on the other hand, the precedence principle or law of the first wavefront, well known to those skilled in the art.
• the location of a sound object is given by the direction from which the sound comes first to the ear (i.e. first wavefront).
• the invention returns, according to this example, to spatialize the left part of the sound stage (given by the left channel of the stereo signal) for the listening position to the left of the separation plane (called left listening position) and to spatialize the right part of the sound stage (given by the right channel of the stereo signal) for the listening position to the right of the separation plane, (the right listening position), the right part of the sound stage being then naturally given for the left listening position by the position of the set of speakers to the right of it, and the left part of the sound stage being naturally given for the right listening position by the position of all speakers located to the left of it.
• the matrices to be reversed in the transaural techniques implemented according to the invention are in fact of reduced dimensions (2x2 matrices in the example envisaged above), since they are limited to each set of speakers. In this way, they suffer little or nothing from the disadvantages of the state of the art (matrices of large dimensions difficult to reverse and poorly conditioned).
• the rendering technique proposed by the invention is thus more robust to the environment of the rendering system.
• the sound reproduction proposed by the invention is less sensitive to the so-called "sweet-spot" phenomenon that the sound reproduction proposed in Dl.
• the "sweet-spot" defines an ideal listening area for which the sound reproduction is designed and optimized: this ideal listening area generally corresponds to a single position in the center of the device.
• the loudspeakers of the two sets of restitution are substantially aligned on a horizontal axis of the rendering system.
• Such a configuration of speakers has a preferred application in a small space such as a car interior for example.
• the virtual source is preferentially created at the intersection of the first line and the horizontal axis of the rendering system, so as to optimize the spatial reproduction of the signal. multichannel sound.
• the generation method further comprises a spectral equalization step during which, for each supply signal intended to supply a loudspeaker, an equalization filter adapted to this particular signal is applied individually. loud speaker.
• This spectral equalization advantageously makes it possible to take into account the environment in which the rendering system is located.
• the rendering system In general, and more specifically when the rendering system is in a closed environment such as for example the passenger compartment of a car, it is to be expected that the timbre of the multichannel sound signal reproduced will not be identical to the two listening positions. Spectral equalization can be implemented to correct this effect. At the same time, for each listening position, it corrects the staining effect due to the transaural technique applied to the set of speakers opposite to the listening position.
• each equalization filter adapted to a loudspeaker is chosen so as to obtain an amplitude spectrum of a frequency response established for this loudspeaker from measurements made in a soundproof environment, in accordance with a first predetermined target spectrum (eg flat amplitude spectrum).
• a first predetermined target spectrum eg flat amplitude spectrum
• the application of this first criterion aims to individually correct the defects of each speaker, and reduce the differences that may appear between them.
• the equalization aims to harmonize the amplitude spectra of the Sequential responses of the different loudspeakers.
• the equalization filters are chosen so as to obtain an average amplitude spectrum evaluated from the impulse responses of the loudspeakers of the sets of the rendering system, according to a second predetermined target spectrum.
• This second criterion aims at a global average equalization of all the power supply signals of the loudspeakers, for example to improve the tone (or coloration) of the restored signal.
• the generation method further comprises a step of spatial analysis of the multichannel sound signal comprising the extraction of at least one sound object and the determination of a spatial position of this sound object, each signal input signal used to generate the speaker power signals of a set of loudspeakers being made from at least one sound object extracted during this spatial analysis step and selected according to its position space relative to the separation plane.
• the invention makes it possible to process any multichannel sound signal and to optimize the rendering of this sound signal, by extracting sound objects from this system.
• the rendering system further comprises a third set of loudspeakers, at least one loudspeaker of this third set being placed on either side of the separation plane.
• This third set of speakers makes it possible to reproduce the sound objects of the multichannel signal whose spatial position determined during the spatial analysis step is in the center.
• each set of speakers of the rendering system comprises a pair of loudspeakers.
• the various steps of the generation method are determined by instructions of computer programs or microprocessors.
• the invention also relates to a computer or microprocessor program on an information carrier, this program being capable of being implemented in a generation device or more generally in a computer or by a microprocessor, this program comprising instructions adapted to the implementation of the steps of a generation method as described above.
• This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape.
• the invention also relates to a computer-readable information medium, comprising instructions of a computer program as mentioned above.
• the information carrier may be any entity or device capable of storing the program.
• the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disk or a disk. hard.
• the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means.
• the program according to the invention can be downloaded in particular on an Internet type network.
• the information carrier may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.
• the invention also provides a sound reproduction system comprising:
• the sound reproduction system comprises at least two sets of loudspeakers located in a front plane with respect to the listening positions and at least two sets of speakers located in a rear plane with respect to the listening positions.
• This embodiment is particularly well suited to the rendering of multichannel signals comprising rear signals, for example signals having a 5.1 format.
• the generation method, the generation device and the system according to the invention present in combination all or part of the aforementioned characteristics.
• FIG. 1 already described represents, schematically, a technique of generalized transaural restitution of the state of the art
• FIG. 2 represents a reproduction system according to the invention comprising a device for generating supply signals intended for loudspeaker assemblies, according to the invention
• FIG. 3 illustrates the hardware architecture of the generation device of FIG. 2
• FIG. 4 represents a reproduction system and a generation device according to the invention in a first particular embodiment of the invention
• FIG. 5 illustrates the main steps of the generation method according to the invention as they are implemented by the generation device of FIG. 4 in the first embodiment
• FIGS. 6A and 6B illustrate how the equalization filters that can be used during the generation process shown in FIG. 5 can be determined
• FIG. 7 illustrates a variant of the first particular embodiment of the invention
• FIG. 8 represents a reproduction system and a generation device according to the invention in a second particular embodiment of the invention.
• FIG. 9 illustrates the main steps of the generation method according to the invention as implemented by the generation device of FIG. 8 in the second embodiment.
• FIG. 10 represents a reproduction system and a generation device according to the invention in a third particular embodiment of the invention.
• a reproduction system 1 comprising a plurality of sets of loudspeakers El. , ..., EN, (N greater than or equal to 2), and a device 2 for generating supply signals to these sets of loudspeakers, according to the invention.
• Each set of loudspeakers includes at least one pair of loudspeakers and is associated with a determined listening position, this listening position being centered here with respect to this set of loudspeakers, so that at least a loudspeaker of the set is located on both sides of the listening position.
• the loudspeakers of each set are positioned on either side of a vertical plane passing through the listening position and parallel to a vertical separation plane situated between the two sets of loudspeakers.
• each listening position is centered relative to the set of speakers with which it is associated is not limiting in itself: the speakers of a set of speakers can be arranged asymmetrically with respect to the listening position.
• the sets of speakers El, ..., EN can be mounted on separate physical entities or on the contrary on the same entity while delimiting distinct areas of space.
• the generation device 2 is not necessarily located on the same physical entity as the speaker sets.
• the generation device 2 has the hardware architecture of a computer, as illustrated schematically in FIG.
• a processor 3 a read-only memory 4, a random access memory 5, a non-volatile memory 6 and communication means 7 on the one hand with a source supplying it with the multichannel sound signal S (not shown in FIG. 2) and on the other hand, with the loudspeakers of the loudspeaker sets El,..., EN to which the generating device 2 supplies the power signals that it has generated.
• These communication means may be for example wired communication means, or alternatively, wireless communication means using WiFI (Wireless FIdelity) for example or Bluetooth TM.
• the read-only memory 4 of the generation device 2 constitutes a recording medium in accordance with the invention, readable by the processor 3 and on which is recorded a computer program according to the invention, comprising instructions for the execution of the steps of a generation method according to the invention described later with reference to Figures 5 and 9, in various particular embodiments.
• This computer program defines, in an equivalent way, functional modules of the generation device 2 (ie module of generation, generation module and if appropriate sound signal analysis module S and equalization).
• FIG. 4 envisages a system for reproducing a stereo signal S 'comprising two sets of loudspeakers E1' and E2 ', each set comprising a pair of loudspeakers (FIG. Hll ', H12' for the set E1 'and ⁇ 2, H22' for the set E2 ').
• the two sets El 'and E2' are located on either side of a vertical separation plane D '.
• the vertical separation plane D ' defines a plane of symmetry for the two sets of loudspeakers El' and E2 '.
• the speakers Hll ', ⁇ 12', ⁇ 2, H22 ' are, in the example illustrated in Figure 4, aligned or substantially aligned on the same horizontal axis ⁇ ' of the rendering system.
• the invention is however not limited to such an aligned configuration of the loudspeakers.
• the loudspeakers H11 'and H22' may be on the axis ⁇ 'while H 12' is positioned above the axis ⁇ 'and ⁇ 2 below, and so on.
• Each set of speakers El ', E2' is positioned facing a privileged listening position PI ', P2'. These listening positions are located on vertical planes Ll 'and L2' respectively, which are parallel to the separation plane D '.
• the listening positions PI 'and P2' are not necessarily one-off.
• PI 'and P2' are located on a plane parallel to the separation plane since their geometric center is located on this parallel plane.
• the listening position PI ' is centered with respect to the set of loudspeakers E1', in other words, the plane L1 'is a median plane of the set of loudspeakers E1'. speakers El ', orthogonal to the axis ⁇ '.
• the listening position P2 ' is centered with respect to the set of loudspeakers E2', that is, the plane L2 'is a center plane of the set of loudspeakers E2' orthogonal to the loudspeaker assembly E2 '. 'axis ⁇ '.
• the listeners i.e. listening positions
• the loudspeakers are placed symmetrically with respect to the separation plane D '.
• the two sets of speakers El 'and E2' are placed asymmetrically with respect to the separation plane D '.
• the signal S ' is a stereo signal composed of two left and right channels, denoted respectively SL' and SR '.
• the generating device 2' On receiving the sound signal S ', the generating device 2' implements a spatial analysis of this signal (step E10), in order to identify the components (ie sound objects) of this signal intended to be restored on the different sets of speakers.
• the sound signal S ' is a stereo signal in the example envisaged in FIG. 4, this spatial analysis is limited here to associating with the first set of speakers El' situated to the left of the separation plane D 'in the space of sound reproduction, the left channel SL 'of the stereo signal, and the second set of speakers E2' located to the right of the separation plane D 'in the sound reproduction space, the right channel SR' of the stereo signal.
• the signals SL 'and SR' are input signals in the sense of the invention for the set ⁇ and for the set E2 'respectively.
• the generation device 2 applies two different transaural techniques to each of the input signals SL' and SR '.
• Each set of speakers El 'and E2' is thus treated separately according to the invention.
• the generation device 2 applies a first transaural technique Tl' to the input signal SL 'so as to create a virtual source VI' in a direction symmetrical with respect to the plane L1 ' passing through the listening position PI 'to the direction of the speaker of the set E2' furthest from the listening position PI ', in other words to the direction of the speaker H22'.
• This virtual source VI ' is created, in the example envisaged in FIG. 4, at the intersection of the axis ⁇ ' and of the straight line d11 '(first straight line within the meaning of the invention) passing through the position of listening PI 'and symmetrical of the line dl2' (second right in the sense of the invention) connecting the listening position PI 'to the speaker H22'.
• VI ' is the symmetrical (in distance and direction) of the loudspeaker H22' with respect to the plane L1 '.
• the listener at the listening position PI ' has a sound scene extending between the direction given by the virtual source VI' (that is to say by the right dll ') and the direction given by the loudspeaker H22 '(i.e., the line dl2').
• the virtual source VI' can also be created on the right dll 'so as to be the symmetrical direction and distance of the speaker H22 'relative to the plane L1'.
• the implementation of the invention does not require that a symmetry in terms of distance is imperatively respected. It is enough that the source virtual VI 'is created on the right dll', that is to say in a direction symmetrical to the direction dl2 'relative to the plane Ll', that the speakers are aligned or not on the same axis.
• the step E20 is implemented by the generation device 2 'by filtering the signal SL' by transaural filters determined so as to create the virtual source VI '.
• these transaural filters are defined in such a way that the listener at the listening position PI 'receives on his two ears two binaural signals which define the virtual source VI'.
• ZI ' is an acoustic transfer matrix between the input signal SL' and the two signals received respectively by the ears of the listener at the listening position PI '(ZI' is in fact a two-component vector in the example envisaged here),
• - ⁇ is a transaural processing matrix between the input signal SL 'and the two power supply signals of the loudspeakers H 11' and H 12 '(Yl' represents the transaural filters and is also a two-component vector in the example envisaged here), and
• the transaural filters applied to the signal SL ' are obtained by inversion of the matrix XI' and multiplication of the inverse matrix thus obtained by the matrix ZI '.
• ⁇ contains the binaural filters which correspond to the creation of the virtual source VI '
• XI' contains the impulse response of the loudspeakers ⁇ 1 and H12 '.
• the matrix XI ' is composed of four acoustic paths, namely the path between the loudspeaker H 11' and the left ear of the listener placed at P1 ', the path between the loudspeaker H11' and the right ear of the listener, the path between loudspeaker H12 'and the left ear of the listener and finally the path between loudspeaker H12' and the right ear of the listener. It can be determined in different ways. For example, as examples:
• - XI 'can be simulated using a database of functions H RTF and extracting the HTRF in the direction of the speakers Hll' and H12 'relative to the listener at the listening position PI'; or - XI 'can be simulated with HTRF functions corresponding to a spherical head model well known to those skilled in the art.
• transaural matrix filters ⁇ thus determined to the signal SL 'results in two power supply signals SU' and S12 'intended to feed respectively the two loudspeakers H11' and H12 'of the set E1'.
• these power signals SU 'and S12' are equalized by means of individual equalizing filters F1 ', F2' before being supplied to the loudspeakers H11 'and H22' (step E30).
• This spectral equalization step is intended to compensate for the possible defects of the speakers H11 'and H12' (for example, the tone of the speakers), and to reduce the differences that may exist between these different speakers.
• the equalization filters F1 'and F2' respectively applied to the signals SU 'and S12' are of course predetermined during a preliminary step, and stored in the nonvolatile memory of the generation device 2 '.
• the average impulse response is then transformed into a frequency response, in a manner known per se, for example by means of a Fourier transformation.
• This average frequency response is then optionally smoothed by frequency band (eg octave bands or auditory bands).
• the equalization filter is then chosen so as to obtain an amplitude spectrum of the optionally smoothed frequency response in accordance with a predetermined target amplitude spectrum SPcible (first target spectrum in the sense of the invention).
• This target amplitude spectrum is for example a flat spectrum, that is to say constant whatever the frequency.
• the equalization filter Fl ' is chosen so as to minimize the difference between SP1 'and SPcible, respectively between SP2' and SPCible, within a limit for example of plus or minus 5dB. This ensures that, on average, the amplitude spectrum of the frequency response of each speaker of the set of speakers El is identical or similar to the amplitude spectrum SPCible and therefore between them. It should be noted that in the example considered here, only the amplitude of the impulse response of each speaker is corrected, it is not interested in the phase itself.
• the filtering of the signal SU 'by the filter F1' results in a filtered feed signal SI 1f, which is supplied by the device 2 'to the loudspeaker ⁇ 1 for reproduction (step E40).
• the filtering of the signal S12 'by the filter F2' results in a filtered feed signal S12f, which is supplied by the device 2 'to the loudspeaker H 12' for reproduction (step E40).
• the generation device 2 Similarly, and in parallel with steps E20-E40, the generation device 2 'applies a second transaural technique 12' to the input signal SR 'so as to create a virtual source V2' in a direction symmetrical with respect to the plane L2 'passing through the listening position P2' to the direction of the loudspeaker of the set ⁇ furthest from the listening position P2 ', that is to say the loudspeaker H 11' (step E50)
• This virtual source V2 ' is created, in the example envisaged in FIG. 4, at the intersection of the axis ⁇ ' and of the straight line d22 '(first straight line within the meaning of the invention) passing through the position of listening P2 'and symmetrical to the line dl2' (second right in the sense of the invention) connecting the listening position P2 'to the loudspeaker H 11'.
• the listener at the listening position P2 ' has a sound stage extending between the direction given by the virtual source V2' (that is to say, by the line d22 ') and the direction given by the loudspeaker ⁇ 1 (that is, the line dl2 ').
• the step E50 is implemented by the generation device 2 'by filtering the signal SR' by transaural filters determined so as to create the virtual source V2 '.
• These transaural filters are determined similarly or identically to the transaural filters applied during step E20 for the creation of the virtual source VI 'and will therefore not be described again here.
• these supply signals S21 'and S22' are equalized by means of individual equalization filters F3 ', F4' before being supplied to the speakers ⁇ 2 and H22 '( step E60).
• This spectral equalization step is intended to compensate for any speaker faults (for example, the tone of the speakers), and to reduce the differences that may exist between the different speakers (ie between H21 'and H22 ' right here).
• the equalization filters F3 'and F4' respectively applied to the signals S21 'and
• step E70 the filtering of the signal S22 'by the filter F4' results in a filtered feed signal S22f supplied to the loudspeaker H22 'for reproduction.
• the filters F1 ', F2', F3 ', F4' are determined so as to compensate for possible defects of the loudspeakers H 11 ', H 12', H21 'and H22' respectively , and to harmonize the timbre of these speakers.
• FIG. 6A illustrates a network of four microphones ml, m2, m3 and m4 duly positioned for the system.
• the impulse responses thus measured are averaged over the set of loudspeakers for each microphone so as to obtain an average impulse response for each microphone.
• the average impulse responses are transformed into frequency responses using a Fourier transform for example.
• Frequency smoothing of the frequency responses thus obtained can be achieved (for example by octave or by auditory band).
• the frequency average of the amplitude spectra of the possibly smoothed frequency responses associated with the microphones is then evaluated.
• the average amplitude spectrum thus obtained thus includes the contribution of all the speakers of the system of restitution the on all the microphones ml, m2, m3 and m4.
• the equalization filters to be applied to the supply signals before they are supplied to the loudspeakers are then chosen so as to obtain a spectrum of average amplitude (in a tolerance for example of +/- 5dB) with a spectrum of predetermined target amplitude SPcible '(second frequency response in the sense of the invention).
• This target amplitude spectrum is for example a flat spectrum, as shown in FIG. 6B, that is constant regardless of the frequency.
• the filters making it possible to improve the timbre of the system as a whole can be applied alternatively to the filters FI ', F2', F3 ', F4' previously described, or in addition to these filters ( applies the two sets of filters successively or equivalent filters to the supply signals).
• the sets of loudspeakers E1 'and E2' each comprise a pair of loudspeakers.
• the invention can also be applied in a similar manner to a different configuration of speaker assemblies El 'and E2', as illustrated in FIG. 7.
• each set of loudspeakers El 'and E2' comprises three loudspeakers H 11 ', H12', H13 'and ⁇ 21', ⁇ 22 ', H23' respectively.
• the virtual source VI ' is then created at a position symmetrical with respect to the plane L1' of the position of the loudspeaker H23 ', while the virtual source V2' is created at a position symmetrical with respect to the plane L2 'of the position of the loudspeaker H 11 '.
• FIG. 8 a system for rendering 1 "of a stereo signal S" comprising two sets of loudspeakers E1 "and E2" arranged similarly to the sets E1 'and E2' of Figure 4, on either side of a vertical separation plane D ".
• Each set of speakers El “, E2” is placed facing a preferred listening position PI “, P2" defined in a manner similar to that previously described for PI 'and P2', and comprises a pair of high speakers (H11 “, H12” for the set E1 “and H21", H22 “for the set E2”).
• PI "and P2" are respectively located on vertical planes L1 “and L2" parallel to the separation plane D. "A loudspeaker of the set E1” is thus positioned on either side of L1 "and the listening position PI ", and a speaker of the set E2" is positioned on either side of L2 "and the listening position P2".
• the reproduction system 1 "further comprises a third set E3" of two loudspeakers H31 “and H32" placed in the center of the reproduction system 1 ", between the two sets E1" and E2 ", as illustrated in FIG. 8. More precisely, the set of loudspeakers E3 "is positioned at the level of the separation plane D": at least one loudspeaker of the set E3 "is placed on either side of the separation plane D ".
• the speakers H11 “, H12", H21 “, H22”, H31 “and H32” are in the example illustrated in Figure 8, aligned or substantially aligned on the same horizontal axis ⁇ "of the reproduction system. as mentioned above, this hypothesis is not limiting and no limitation is strictly attached to the placement of the loudspeakers of the sets El “, E2" and E3 "with respect to this horizontal axis.
• the generation device 2 On reception of the sound signal S ", the generation device 2" implements a spatial analysis of this signal (step F10), in order to identify the components (ie sound objects) of this signal which will be restored on the different sets of speakers.
• the analysis step F10 comprises a decomposition of the sound signal S "into several frequency sub-bands (eg in octave, or into auditory bands depending on the available processing power to implement the invention).
• the device 2 "extracts on each frequency subband the sound objects contained in the signal S", and determines for each sound object, its spatial position.
• the device 2 "then generates from the sound objects thus extracted three input signals denoted SL", SR "and SC" for the three sets of speakers El “, E2” and E3 ".
• the sound objects selected for each input signal depend here on their spatial positions with respect to the separation plane D "(and more generally predetermined analysis criteria which determine to which set of loudspeakers to send which sound object according to its spatial position)
• D the separation plane D
• the generation device 2 "applies two different transaural techniques to each of the input signals SL" and SR ", similarly to what has been described previously with reference to FIG. F20 and F50 for applying a transaural technique resulting in the creation of two virtual sources VI “and V2", the spectral equalization steps F30 and F60 by the filters F1 ", F2", F3 “and F4", and the steps F40 and F70 for generating the power supply signals to the loudspeakers of the sets E1 "and E2" being identical respectively to the steps E20 and E50, to the steps E30 and E60, and to the steps E40 and E70, they are not described again here.
• the generation device 2 also applies a spatial rendering technique T3" to the input signal SC "in order to generate the power signals of the speakers H31 “and H32" of the third central speaker set E3 "(step F80).
• This rendering technique is chosen for example so as to directly broadcast the signal SC "on the speakers H31" and H32 ".
• the supply signals S31 "S32” generated by applying the technique T3 "to the input signal SC” are then filtered using equalization filters (which can be determined according to a method similar to that explained previously to determine filters FI ', F2', F3 'and F4') (step F90).
• the spatial reproduction technique T3 "applied to the input signal SC" generates supply signals for the loudspeakers of the three sets E1 “, E2” and E3 ", using a technique of holophonic rendering such as for example a WFS technique (for Wave Field Synthesis)
• a technique of holophonic rendering such as for example a WFS technique (for Wave Field Synthesis)
• this second embodiment can be declined according to the different variants previously envisaged for the first embodiment.
• the invention also applies to other types of multichannel signals, for example to a multi-channel 5.1 signal.
• FIG. 10 illustrates a reproduction system 1 "'according to a third embodiment, allowing the reproduction of a sound signal S'" 5.1, composed of a left channel (SL '"), of a right channel (SR '"), a left rear channel (SLs'”), a right rear channel (SRs '”), a center channel (SC”), and a bass channel (SLfe' ”) .
• the reproduction system 1 "'comprises two subsystems" front “A and” rear “B, respectively placed in front of and behind the listening positions PI'" and P2 '"(with respect to the positioning of the listeners at these positions d 'listening).
• the subsystem A comprises three sets of loudspeakers ⁇ ", EA2 '” and EA3' "arranged with respect to the listening positions PI '" and P2 ", and with respect to the vertical separation plane D'" so identical to the sets of speakers El “, E2” and E3 "considered previously to illustrate the second embodiment.
• the subsystem B further comprises two sets of loudspeakers EB1 '' and EB2 '' disposed rearward of the listening positions PI '' and P2 '' identically to the loudspeaker assemblies E1 'and E2 'considered previously to illustrate the first embodiment.
• EBl '"and ⁇ 2 '" are placed on either side of the vertical separation plane D'", and are respectively centered with respect to the vertical planes L1 '"and L2'" which are parallel to the separation plane D '"and pass through PI '"and P2'" respectively.
• the reproduction system 1 "'thus comprises a frontal array of loudspeakers comprising the sets EA1'", EA2 '"and EA3'" which is located in a front plane with respect to the listening positions PI '"and P2' and a rear speaker array comprising the sets EB1 "and EB2 '" which is in a rear plane with respect to the listening positions PI' "and P2 '".
• the channels SL '"and SR'" are used to generate power supply signals of the speaker assemblies ⁇ "and EA2 '" respectively, as previously described in the first embodiment, resulting in the creation of two sources virtual VA1 '"and VA2'";
• the channel SC " is used to generate signals of supply of the loudspeakers of the third set EA3 '" of loudspeakers of the subsystem A, by applying a technique of spatial restitution directly on these channels, as described previously for the input signal SC "in the second embodiment;
• the channels SLs' "and SRs'” are used to generate supply signals of the speaker assemblies ⁇ "and EB2 '" respectively, as previously described in the first embodiment, resulting in the creation of two sources virtual VB1 '"and VB2'", as shown in Figure 10;
• the SLFE channel is used to generate a signal for powering a subwoofer not shown in FIG.
• the "rear" subsystem B may be an exact replica of the "forward" subsystem A, symmetrical with respect to the listening positions PI '"and P2'".
• different loudspeaker configurations may be envisioned for both subsystems (eg, three sets of two speakers for A and two sets of two speakers for B, as illustrated in Figure 10).

Landscapes

• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Acoustics & Sound (AREA)
• Signal Processing (AREA)
• Circuit For Audible Band Transducer (AREA)
• Stereophonic System (AREA)
• Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=48225019

Family Applications (1)

Country Status (3)

Family Cites Families (5)

• 2013
  • 2013-02-18 FR FR1351352A patent/FR3002406B1/fr not_active Expired - Fee Related
• 2014
  • 2014-02-14 EP EP14710015.0A patent/EP2957110B1/de active Active
  • 2014-02-14 WO PCT/FR2014/050313 patent/WO2014125232A1/fr active Application Filing

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events