EP0025509B1 - Procédé de transmission stéréophonique et moyens pour la mise en oeuvre de ce procédé - Google Patents

Procédé de transmission stéréophonique et moyens pour la mise en oeuvre de ce procédé Download PDF

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Publication number
EP0025509B1
EP0025509B1 EP19800104718 EP80104718A EP0025509B1 EP 0025509 B1 EP0025509 B1 EP 0025509B1 EP 19800104718 EP19800104718 EP 19800104718 EP 80104718 A EP80104718 A EP 80104718A EP 0025509 B1 EP0025509 B1 EP 0025509B1
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Prior art keywords
transmission
hand
sound
filter
signals
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Expired
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EP19800104718
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German (de)
English (en)
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EP0025509A1 (fr
Inventor
Peter Schöne
Helmut Lamparter
Jürgen Oelmann
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SCHOENE, PETER, DR.-ING.
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Schone Peter Dr-Ing
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Priority claimed from DE19792932330 external-priority patent/DE2932330A1/de
Priority claimed from DE19792944851 external-priority patent/DE2944851C2/de
Priority claimed from DE19803001007 external-priority patent/DE3001007C2/de
Priority claimed from DE19803003852 external-priority patent/DE3003852C2/de
Application filed by Schone Peter Dr-Ing filed Critical Schone Peter Dr-Ing
Priority to AT80104718T priority Critical patent/ATE5458T1/de
Publication of EP0025509A1 publication Critical patent/EP0025509A1/fr
Application granted granted Critical
Publication of EP0025509B1 publication Critical patent/EP0025509B1/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04S—STEREOPHONIC SYSTEMS 
    • H04S1/00—Two-channel systems
    • 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
    • H04R5/027—Spatial or constructional arrangements of microphones, e.g. in dummy heads

Definitions

  • the invention relates to a method for the stereophonic transmission of sound signals by means of an artificial head which has a directional characteristic largely approximated to human hearing and whose microphone signals are equalized by electrical filtering, and by means of a headphone which is free-field-equalized for a reference direction.
  • a head-related transmission arrangement suitable for carrying out such a method is described in the journal article “Head-related stereophony”, Funkschau 52, Issue 9, April 1980, pp. 79-84.
  • a headphone which is equalized according to DIN 45 500, i.e. headphones which, in contrast to so-called distortion-free headphones, simulate the transfer function of the natural head.
  • DIN 45500 from September 1975, the reference direction for this free field equalization is a frontal sound incident on the listener.
  • an artificial head is provided on the recording side, which is equalized by an electrical filtering - a so-called free-field adaptation filter - in such a way that the transfer function of the head-related recording arrangement is frequency-independent.
  • This electrical equalization of the receiving side is carried out for frontal incidence of the artificial head.
  • the stereo signals are recorded on a sound carrier (e.g. record, tape) and / or transmitted on a transmission line (e.g. stereophonic radio channel).
  • a sound carrier e.g. record, tape
  • a transmission line e.g. stereophonic radio channel
  • This head-related transmission method avoids some shortcomings that adhere to the basic idea of head-related stereophony (lifelike acoustic head replica on the one hand and distortion-free headphones on the other).
  • the so-called compatibility with conventional spatial stereophony which is a major problem with head-related transmission methods, is improved by the free field adaptation of the recording side, i.e. the free-field-adapted artificial head signals are much better suited for spatial playback via loudspeakers than artificial head signals with the frequency evaluation of ear signals.
  • a free-field-adapted dummy head can also be standardized in the same way as a conventional stereo microphone for spatial recording technology.
  • the remaining disadvantages of this head-related transmission method are due to the limitation of the free-field adaptation on the recording side and the free-field equalization on the reproduction side to frontal sound incidence.
  • the speaker setup is not limited to the frontal direction of sound, but stereo speakers are usually not set up frontally, especially laterally.
  • the conventional room-related recording technology not only are microphones with a frequency-independent transmission dimension used for frontal sound, but also, for example, microphones with a frequency-independent transmission standard for diffuse sound.
  • an artificial head usually not only records frontal sound sources, but also a whole panorama of spatially distributed sound sources, the restriction to frontal sound as reference sound for the free field adjustment of the artificial head can lead to an unnecessarily large compatibility error, i.e. the timbre of an artificial head recording can be impaired compared to a conventional stereo recording of the same sound source panorama.
  • the second disadvantage which is basically associated with the restriction to only one reference direction, relates to the true-to-original localization of the sound sources in the different directions.
  • a sound source is localized with the aid of the directional characteristic of the hearing, that is to say with the aid of the frequency-dependent differences in amplitude and transit time between the two ear signals.
  • the individually different head geometry of different listeners leads to a noticeably different directional characteristic.
  • the dependence of the left-right ear signals on the direction of sound incidence is therefore somewhat different for each individual listener.
  • Each listener has learned the correct assignment of a sound incidence direction to the received ear signals for their directional characteristics individually. It was confirmed by listening tests that changes in this directional characteristic caused by a changed head geometry, for example by the head geometry of another listener, lead to corresponding positioning errors.
  • the object of the invention is therefore to provide a head-related transmission method which is compatible with the spatial stereophony with respect to timbre and localization and which adapts the directional characteristic of the Artificial head to the individual directional characteristics of the listener.
  • the invention solves this problem in that the frequency response of the recording-side filter arrangement is inverse to the free-field transmission dimension of the microphones arranged in the artificial head for the reference direction of the free-field equalization of the headphones on the basis of the fact that the artificial-head signals thus generated are fed to a decoupling device on the recording side, which decouples the head-related stereo signals to which the signals originating from a sound source are each present in both microphone channels, decoupled according to the transfer functions of the artificial head for two lateral sound incidence directions to spatial stereo signals, and that the reproduction takes place via a circuit arrangement for adapting the spatial stereo signals to the headphones, which the spatial stereo signals ( decoupled artificial head signals) according to the transfer functions of the individual listener for these two lateral sound incidence directions in head-related stereo signal e coupled.
  • the first characteristic feature states that the artificial head is freely adapted to a selectable reference sound system that is compatible with the spatial stereophony using the recording-side electrical filtering, and that this recording-side reference sound system is identical to the playback side that is used as the basis for the free-field equalization of the headphones.
  • This correspondence of the reference sound systems for the respective equalization which can be carried out independently of one another, ensures that the improvement of the compatibility with regard to the timbre of the artificial head signals in the case of any spatial reproduction via loudspeakers is not at the expense of the fidelity with normal reproduction of the artificial head signals via headphones.
  • the second characteristic first improves the compatibility with the spatial stereophony in terms of the location of the sound sources.
  • the decoupling oriented at the artificial head has the effect, in particular, that the sound signals picked up by the artificial head from two spatially separated sound sources are decoupled in such a way that these sounds can be stored and / or transmitted separately and can be reproduced separately with respect to the two predefined lateral directions of sound incidence.
  • this decoupling virtually eliminates the directional characteristic of the artificial head. This is the precondition for the fact that the directional characteristic of the artificial head can be replaced by the individual directional characteristic of the listener with the aid of the circuit arrangement according to the third characteristic.
  • Claims 2 to 12 specify transmission elements which are particularly suitable for carrying out the method according to the main claim.
  • the artificial head according to claim 2 has a particularly large signal-to-noise ratio because of the nature of the microphones provided. Because of the installation of the electrical components according to claim 3, it is particularly compact and easy to handle.
  • the filter arrangement according to claims 4 to 6 allows an expedient free field adaptation of the artificial head signals without deteriorating the acoustic signal-to-noise ratio of the artificial head due to self-noise of the electrical filter.
  • the decoupling device according to claims 7 to 9 has an advantageous and clear circuit structure in which the transfer functions of the individual transfer elements can be derived directly from only four measurements on the artificial head.
  • circuit arrangement according to claim 10 shows a particularly precise, the circuit arrangements according to patent claims 11 and 12 show particularly simple implementations of the filter on the reproduction side.
  • the transmission arrangement shown in FIG. 1, which is suitable for carrying out the method according to the invention, consists on the receiving side of the artificial head A with built-in microphones A1 and equalizer filters A2 and a decoupling device B, on the reproduction side of a circuit arrangement C inverse to the decoupling device B and the headphones D.
  • This arrangement is a true-to-original transmission of sound events possible.
  • the basic approach of head-related stereophony is that the natural spatial hearing should be simulated with the help of an artificial head and headphones.
  • the aim is to generate the same ear signals in a subject's ear canal by means of head-related stereophony as would occur with natural hearing if the subject's head were located directly at the location of the artificial head recording. If this goal is achieved with sufficient accuracy, the head-related stereophony leads to a spatial mapping of sound sources with a quality that has never been achieved by any other stereophonic method.
  • the first requirement is met relatively well for the middle listener in the most widespread prior art (artificial head according to DE-PS 1 927401).
  • the transmission function of the headphones used corresponds to the requirements of DIN 45 500 for high-quality headphones.
  • Such free-field-equalized headphones produce the same ear signals in a test subject's ear canal as a loudspeaker with a frequency-independent transmission function, which stands a few meters in front of the test subject.
  • the headphones have the same transfer function as the outer human ear.
  • These free-field equalized headphones emulate the outer ear function for frontal sound.
  • the microphone signals are approximately electrical equivalents to ear signals.
  • the outer ear function for frontal sound incidence in the artificial head is therefore once again and thus contains too much overall, which leads to the aforementioned deviation from natural hearing.
  • the external ear transmission function of the artificial head contained in the artificial head-headphones transmission chain is excessively compensated so that the transfer function of the entire artificial head arrangement A, including the microphones A1 with a downstream filter arrangement A2, is frequency-independent for frontal sound incidence.
  • the listener has a largely natural sound color impression due to the outer ear transmission characteristic of the free-field equalized headphones.
  • a major advantage is that the free-field-matched (equalized) artificial head signals convey a better sound color impression than the stereo signals from an artificial head according to DE-PS 1 927401, even when reproduced by loudspeakers, as could be determined by practical tests.
  • Fig. 2 to illustrate this problem for a free-field equalized headphones D
  • Fig. 3 for an artificial head according to DE-PS 1 927 401
  • the frequency response of the transmission mass is shown.
  • the improved prior art consists in compensating the frequency response of the artificial head for frontal sound incidence on the receiving side with the aid of the filter arrangement A2, as is indicated in FIG. 3 by the curve shown in dashed lines.
  • the filter arrangement A2 shown in FIG. 4 using an exemplary embodiment and also suitable for carrying out the method according to the invention according to claim 4 consists of the chain connection of a bandpass filter A10 and two band-stop filters A20, A30, the circuit components A10, A20 and A30 being separated from one another by vertical dashed lines are.
  • the band pass A10 and the band stops A20, A30 are designed in the form of bridge T-elements.
  • the transverse branch of the bandpass filter A10 comprises a parallel resonant circuit with an inductance L "of a capacitance C, and an ohmic resistor R" and a series resistor R 2 .
  • the bridge branch of the band pass A10 comprises a series resonant circuit with an inductance L 3 , a capacitance C 3 and an ohmic resistor R 3 , and also a parallel resistor R 4 '.
  • the longitudinal branch of the band pass A10 comprises two ohmic resistors R. This applies in the same way also for the longitudinal branches of the two band stops A20 and A30.
  • the transverse branch comprises a series resonant circuit with an inductance L 5 , a capacitance C 5 and an ohmic resistor R e .
  • the bridge branch of the bandstop A20 comprises a parallel resonant circuit with an inductance L e , a capacitance C e and an ohmic resistor R e .
  • the transverse branch comprises a series resonant circuit with an inductance L 7 , a capacitance C 7 and an ohmic resistor R ,.
  • the bridge branch of the band-stop filter A30 comprises a parallel resonant circuit with an inductance L e , a capacitance C e and an ohmic resistor R e .
  • the input A11 of the filter assembly of FIG. 4 is connected upstream for impedance matching, an ohmic resistor R e.
  • a practically implemented filter arrangement A2 according to FIG. 4 had a switch-on attenuation of 37 dB for a broadband signal. Due to the exclusive use of passive components, the filter arrangement A2 according to FIG. 4 showed practically no intrinsic noise.
  • the mode of operation of the filter arrangement A2 according to FIG. 4 can best be seen from the frequency response according to FIG. 3 (curve drawn in dashed lines).
  • the bandpass A10 increases the frequency response at 10 kHz, while the band-stop filters A20, A30 cause the cuts at 1.4 kHz and 4.2 kHz.
  • the described artificial head can only be used on the condition that the headphones used are free-field equalized for frontal sound.
  • the method can also be used for headphones which are free-field-equalized with respect to other sound incidence directions if the filter arrangement A2 is modified in accordance with claim 5.
  • the modified method takes into account the other direction of sound incidence in the free field equalization of the headphones in that the amplitude frequency response of the adaptation filter A2 is inverse to the free field transmission dimension of the artificial head for the other sound direction.
  • the listener receives natural ear signals even if the headphones D used are not free-field equalized according to DIN 45 500, part 10 from September 1975 for frontal sound.
  • FIG. 5 shows the different frequency responses G F of headphones with frontal or deviating free field equalization.
  • the headphones indicated by a solid curve compared to headphones indicated by a dashed curve and frontally free-field-equalized in a known manner, essentially show an increase in height at a frequency of approximately 10 kHz.
  • the consideration on which the modified method is based now consists in compensating for this frequency response sum of the artificial head on the one hand and headphones with a different reference direction of the free field equalization on the other hand on the receiving side with the aid of the filter arrangement A2, as is indicated in FIG. 6 by the curve drawn in dashed lines.
  • the frequency response of the free-field transmission mass of the listener's outer ear becomes effective for the selected direction of sound incidence, so that the listener retains the natural sound color impression even when the reference direction changes.
  • the filter arrangement A2 shown in FIG. 4 is also suitable for carrying out the modified method.
  • the opposite compensation of the transfer function of the artificial head is achieved with the aid of a filter arrangement A2, which, for. B. consists of the derailleur of a bandpass and two bandstops.
  • A2 which, for. B. consists of the derailleur of a bandpass and two bandstops.
  • an artificial head according to claim 2 is suitable.
  • a structurally particularly favorable design of such an artificial head is specified in claim 3.
  • microphones A1 are expediently used which have a resonance in the frequency range between 5 and 12 kHz have a center.
  • Electret microphones or condenser microphones are suitable for this.
  • a passive band stop can be used with this artificial head for the filter arrangement A2 for screening the remaining peaks. All components, such as microphone amplifier A3, filter A2 and power supply can be advantageously installed in the artificial head, whereby a simple, clear handling is achieved.
  • the curve shown in FIG. 7 shows the frequency response of a known electret microphone which has a resonance peak in the range between 2 and 12 kHz.
  • the resonance point at 9 kHz is selected so that it matches the artificial head used.
  • a suitable filter arrangement A2 is, for example, the passive bandstop illustrated in FIG. 9, which has a T branch and a bridge branch R " , L 11 , C 11 and an upstream series resistor R 9 and a downstream parallel resistor R for resistance adjustment.
  • the T branch in its longitudinal section comprises two series resistors R and in its cross section a damped with a series resistor R 10 series-LC-circuit L 10, C 10.
  • the bridge branch of the filter assembly of FIG. 9 consists of a damped by a parallel resistor R 10 parallel LC circuit L 11 , C 11 .
  • FIG. 10 shows a signal branch for processing a stereophonic L or R signal, which consists of the chain connection of the microphone A1, a high-pass filter R 14 , C 14 , a connected operational amplifier OP and the filter arrangement A2.
  • two such signal branches are structurally integrated into the artificial head together with the required power supply (eg battery), so that an easily manageable, clear pick-up device is available.
  • An electret microphone with a frequency response according to FIG. 1 or a condenser microphone with a comparable frequency response is provided as the microphone A1.
  • the high pass R 14 , C 14 which is arranged between the microphone A1 and the non-inverting input of the operational amplifier OP, consists of a series capacitance C 14 and a shunt resistor R 14 and is used to screen very low-frequency interference signals.
  • the inverting input of the operational amplifier OP is connected to a series resistor R 12 for setting the gain factor.
  • the amplifier output is fed back via a negative feedback resistor R 13 to the inverting input of the operational amplifier OP.
  • the embodiment shown in FIG. 9 with a passive bandstop can be considered as filter arrangement A2.
  • the output signals of the artificial head A are fed to the inputs of the decoupling device B.
  • the acoustic influence of the artificial head geometry on the microphone signals M li , M re and the electrical microphone equalization A2 are not shown in the microphone channels 20, 30 in FIG. 11 because they are irrelevant to the principle of the decoupling to be explained .
  • two sound sources S and S 2 as well as two loudspeakers 40 and 50 are indicated for the explanation of the decoupling device B and the solution of the compatibility problem caused by it, which - in relation to the listener position and the reference direction of the listener 100 - have the same sound incidence directions as those assumed sound sources S, and S 2 - based on the center and the reference direction of the microphone arrangement - have.
  • Stereophonic microphone arrangements of various types can be used for recording stereophonic signals, which should be suitable for spatial reproduction, ie for reproduction by means of stationary loudspeakers, which have in common that the distance between the two microphones is small compared to the distance between the microphone arrangement and the sound sources.
  • a li and A re are the free field transfer functions of the left and right microphone, which generally and in particular in the artificial head depend on the frequency f, the side angle ⁇ to a reference direction and the elevation angle 5 above the horizontal plane.
  • the microphone directional characteristic A (f, ⁇ , 8) is independent of the distance of the sound sources if the distance between the sound sources is large compared to the dimensions of the microphone arrangement.
  • a common feature of the stereophonic loudspeaker arrangements for reproducing spatial stereophonic signals is that the distance between the loudspeaker and the listening location is large compared to the head diameter of the listener and the loudspeaker dimensions. Loudspeaker constructions that are median symmetrical with respect to the head position of the listener and have a base width of a few meters with a base angle of approximately 60 ° are of practical importance.
  • the effect of such stereophonic loudspeaker arrangements at the listener location in a not too reverberant environment can generally be determined by the free field transmission function C, (f) and Describe C z (f) and the set-up direction ⁇ 1 , 8, and ⁇ 2 , ⁇ 2 of the two loudspeakers. ⁇ 1 or ⁇ 2 are the side angles to a reference direction, while 8 or ⁇ 2 are the elevation angles above the horizontal plane for the first or second loudspeaker, based on the listener location.
  • Filters with the inverse transmission functions 1 / C, (f) and 1 / C 2 (f), which can be connected upstream of the two loudspeakers, can always ensure that the free-field transmission functions of the loudspeaker arrangement, depending on the listener location, are frequency-independent and that Difference in time to the listener location is compensated.
  • the effect of the speakers then only depends on the setup directions ⁇ 1 , 8, and ⁇ 2 , ⁇ 2 .
  • the signals M 11 , M re from the two microphone channels 20, 30 are converted by means of a decoupling filter B10 during the recording such that when the converted signals L 1 , L 2 are reproduced as loudspeakers, the reproduced sound event is distributed to the original, spatially distributed Sound event corresponds to sound, time and direction.
  • the effort for the two microphone channels 20, 30, i.e. for the artificial head A, and the decoupling arrangement B10 is many times lower in comparison to the recording device mentioned at the beginning with additional support microphones and multi-channel mixing consoles, the reproduction quality achieved with the device B according to the invention compared to this State of the art in spatial stereophony is at least the same and is even better, as has been shown in practical tests. This applies especially when the two microphones are arranged in the artificial head A because the stereophonic signals then contain the natural, head-related spatial information.
  • the 11 comprises on the receiving side the two microphone channels 20, 30, the signals of which are fed to the inputs M li and M re of a decoupling filter B10.
  • the decoupled signals at the outputs L 1 , L 2 of the filter B10 can be recorded on a suitable, two-channel sound carrier or can be sent via separate radio channels.
  • two loudspeakers 40, 50 are provided for the two transmission or sound channels as a technical equivalent to the circuit arrangement C and the headphones D according to the main claim, to which transmission elements 80 and 90 can be connected upstream, in order to require frequency and time-independent sound conversion to be able to.
  • the loudspeakers 40, 50 have the azimuth angles ⁇ 1 and negligence 2 and the elevation angles 8 and ⁇ 2 with respect to the head 100 of a listener. Furthermore, with reference to the two microphone channels 20, 30, the general case of the sound recording of a sound source S with a sound incidence direction ⁇ , 8 with respect to an arbitrary reference direction shown in dash-dotted lines and the case of two sound sources S, and S 2 with the special sound incidence directions ⁇ 1 , ⁇ 1 , and ⁇ 2 , ⁇ 2 illustrated in Fig. 11.
  • the decoupling filter B10 comprises four special transmission elements B15-B18, the transmission functions of which are explained in more detail below.
  • the transmission elements B15-B18 are interconnected in the form of an inverse filter, the transmission element B15 being arranged in the longitudinal branch B11 of the left transmission channel and the transmission element B16 in the longitudinal branch B12 of the right transmission channel.
  • Subtraction elements B13 and B14 are provided between the inputs M li and M re and the transmission elements B15 and B16.
  • the negative input of the subtraction element B13 is connected via the transmission element B18 to the output of the transmission element B16 or the output L 2 in the sense of a reverse negative feedback, while the negative input of the subtraction element B13 via the transmission element B17 to the output of the transmission element B15 or the output L, is connected in the sense of a reverse negative feedback.
  • a symmetry of the loudspeakers 40.50 is not necessary in the general case.
  • the transmission links 80, 90 are omitted.
  • Table 1 shows the transfer function [F] of the decoupling filter B10 for the artificial head A and, in comparison, for the two other practically important stereophonic microphone arrangements. Normally, the microphone arrangements should be median-symmetrical, so that the descriptive matrices are then symmetrical with respect to the main diagonal.
  • decoupling filter B10 there are further transmission elements B61 in the left and right transmission channels M li, L and M re , L 2 in front of and behind the “reduced” decoupling arrangement designated here with B10 * .
  • B71 or B62, B72 arranged.
  • the transfer functions of these further transfer elements B61, B71, B62, B72, namely D li * (f), E 1 * (f), D re * (f) and E 2 * (f) contain split parts of the total transfer function [F] des Decoupling filter B10 according to FIG. 11.
  • the expression “reduced” decoupling arrangement accordingly means the rest of the decoupling arrangement B10 according to FIG.
  • FIG. 11 reduced by the split-off parts of the overall transfer function, which is therefore designated in FIG. 12 with B10 * .
  • the design of the decoupling arrangement B10 according to FIG. 11 and the reduced decoupling arrangement B10 * according to FIG. 12 differ only in the respective transfer function of the transfer elements B15-B18, as will be explained in detail below:
  • the transmission elements B61, B62 arranged in front of the inputs of the reduced decoupling arrangement B10 * with the transfer function [F * ] have the transfer function while the transfer elements B71, B72 indicated behind the outputs of the reduced decoupling arrangement B10 * perform the transfer function have.
  • the reduced decoupling arrangement B10 * then has the transfer function [F * ]: -
  • Table 2 contains the seven possible simplifications of the decoupling arrangement B60, B10 * , B70 according to FIG. 12, which result from the fact that certain pairs of transfer functions are set equal to one.
  • the first line of Table 2 contains the case of the decoupling filter B10 shown in FIG. 11, which is characterized in that all of the decoupling arrangement upstream and downstream transmission elements B61, B71, B62, B72 have the transfer function one. All decoupling arrangements according to Table 12 are equivalent with regard to the transfer function [F], but not with regard to the structural design.
  • the stereo signals recorded with the artificial head A and the decoupling device B are fed to a circuit arrangement C for adapting a spatial stereophonic program signal to a headphone D, as is known as such.
  • Circuit arrangements of this type aim to simulate the direct sound from two stereo loudspeakers in order to generate the same hearing events when using headphones as when using loudspeakers.
  • the known circuit arrangements are on the one hand very complex, on the other hand not precise and therefore not effective enough.
  • the ratio between the technical complexity of the circuitry and the improvement in headphone reproduction achieved (for example in avoiding the so-called in-head localization) is low, so that such a device has so far not been able to establish itself.
  • the free-field transmission dimension of the loudspeakers to be reproduced is to be regarded as immaterial in the sense of the task, because it is irrelevant for the location during loudspeaker reproduction. This is why this loudspeaker characteristic is also unimportant for simulating loudspeaker sound with the aid of headphones, so that in any case it is sufficient to refer to two «ideal» loudspeakers.
  • claims 10 to 12 provide two solutions. They differ in the combination of the transmission properties of the circuit arrangement C and the headphones D. This part of the invention is explained in more detail with reference to the drawings 13 to 19.
  • the circuit arrangement C according to the first approach has the same circuit structure as described in DE-OS 2 007 623 (see FIG. 13a) and consists of four transmission elements C1 or C2 arranged in front of the summing points and two delay elements C3.
  • a significant simplification of the circuit can be achieved in that the transmission element C1 simulates exactly half of the interaural level difference as a level increase on the facing ear, while the transmission element C2 simulates the other half of the interaural level difference as level reduction on the facing ear.
  • half the interaural level difference corresponds to the monaural transmission masses in a very good approximation.
  • this circuit arrangement can be operated together with a free-field equalized headphone D without an audible tone color error, i.e. the circuit arrangement is compatible with any headphones whose free field transmission dimensions are frequency-independent in accordance with DIN 45500.
  • the exact localization is guaranteed by the exact replication of the interaural level difference (Fig. 14) and the interaural time difference (Fig. 15).
  • the circuit arrangement can be simplified by virtue of the fact that the transfer functions of the transfer elements C1 and C2 are reciprocal to one another according to the invention. Therefore, the transmission elements C1 and C2 can be constructed in a very similar manner, as illustrated with reference to FIG. 16.
  • the transmission elements C1 and C2 are implemented by multi-stage (preferably four-stage) resonance circuits of the second order.
  • 16 shows the basic circuit diagram of a soI Chen stage at which the resonance circuit is built using active RC technology.
  • the network contains the ohmic resistors R x and Ry, the exchange of which reverses the functions of the band pass and the band stop. It also contains two adjustable capacitive or ohmic impedances Z, which determine the resonance frequency of the circuit. By adjusting these impedances, the transmission dimension of the multi-stage resonance circuit can be adapted to half the interaural level difference of the individual listener.
  • Delay links C3, consisting of a chain connection of second-order all-pass links , contribute to the simulation of the interaural transit time difference ⁇ i .
  • Four of the resonance circuits shown in FIG. 18 are preferably provided as delay element C3. Their frequency-dependent delay time together with the frequency-dependent delay time difference of the first and second transmission elements C1 and C2 simulates the individual, frequency-dependent delay time difference of the hearing of a particular listener for the direction of sound incidence 30 °.
  • the interaural transfer function can be measured by known measurement methods (e.g. US Pat. No. 4,143,244) and the filters can be optimized by known optimization methods.
  • any transmission elements C1 in the longitudinal branches of the circuit arrangement are dispensed with.
  • the entire interaural transfer function is simulated in the respective cross branch.
  • both the frequency-dependent interaural level difference (FIG. 14) and the frequency-dependent interaural transit time difference (FIG. 15) can be simulated simultaneously.
  • a bandstop filter according to FIG. 18 can either be minimal phase or (with the same amplitude frequency response) generate additional transit times.
  • Each bandstop is determined by three independent parameters (e.g. resistors R 15 , R 18 and R 18 ), so that with four resonance circuits, twelve independent parameters are available to simulate the individual interaural difference.
  • This simplified circuit arrangement is so small and light that it can be built into the headband D of a headphone.
  • the frequency response of the converter is thus inverse to the frequency response of the circuit arrangement C in the event of a frontal hearing event.
  • the output signals of the circuit arrangement C are subject to the frequency response AL (comb filter effect), which is shown in broken lines in FIG. 19, because of the cross coupling (with transit times).
  • AL comb filter effect
  • the reproducing arrangements C, D described in the two approaches are suitable for reproducing all spatial stereo signals, i.e. both conventional stereo signals and those stereo signals of an artificial head A which, for reasons of compatibility, have been converted into spatial stereo signals by the decoupling filter B.

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  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
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  • Stereophonic System (AREA)

Claims (12)

1. Procédé de transmission stéréophonique de signaux acoustiques à l'aide d'une tête d'enregistrement (A), qui possède une caractéristique de directivité voisine de l'oreille humaine et dont les signaux de micro sont corrigés par un filtrage électrique (A2), et à l'aide d'un écouteur (D) corrigé pour une direction de référence, caractérisé en ce que la courbe de fréquence du dispositif de filtrage (A2) est inverse du taux de transmission à champ libre des micros (A1) disposés dans la tête d'enregistrement (A), pour la direction de référence déterminée fondamentalement de la correction à champ libre de l'écouteur (D), en ce que les signaux de la tête d'enregistrement (Mli, Mr.) ainsi générés du côté de l'enregistrement sont appliqués à un dispositif de découplage (B) qui découple les signaux stéréophoniques (Mli, Mr.) issus de la tête, dans lesquels les signaux issus de la source acoustique (par ex. s) sont chaque fois présents dans les deux canaux de micros (20, 30), en signaux stéréo (L,, L2) relatifs à l'espace en fonction des fonctions de transfert 5 (Ali, Are) de la tête d'enregistrement (A) pour deux directions latérales d'impact du son (S1, S2), et en ce que la restitution s'effectue par l'intermédiaire d'un circuit (C) d'adaptation des signaux stéréo relatifs à l'espace (L,, L2) à l'écouteur (D), qui accouple les signaux stéréo relatifs à l'espace (signaux découplés de la tête L,, L2) conformément aux fonctions de transfert de l'auditeur individuel (100) pour ces deux directions d'incidence latérales du son (S1, S2) en signaux stéréo relatifs à la tête (fig. 1).
2. Tête d'enregistrement (A) pour exécuter le procédé selon la revendication 1, caractérisé par l'utilisation de micros à électret (A1) ou de micros à condensateurs (A1), qui présentent une zone de résonance dans la gamme de fréquences entre 5 et 12 kHz.
3. Tête d'enregistrement (A) selon la revendication 2, caractérisée par le dispositif de filtrage (A2) qui est monté dans la tête d'enregistrement (A) avec un amplificateur branché en avant (A3) ainsi qu'avec l'alimentation en courant.
4. Dispositif de filtrage (A2) pour exécuter le procédé selon la revendication 1, caractérisé en ce que sa courbe de fréquence (figs 3 et 8) est inversée par rapport au taux de transfert à champ libre des micros (A1) disposés dans la tête d'enregistrement (A) pour l'incidence frontale du son, qui sert simultanément de référence acoustique à la correction à champ libre du côté restitution (figs 2, 5) de l'écouteur (D).
5. Dispositif de filtrage (A2) pour exécuter le procédé selon la revendication 1, caractérisé en ce que sa courbe de fréquence (fig. 6) est inversée par rapport au taux de transfert des micros (A1) disposés dans la tête d'enregistrement (A) pour l'incidence acoustique non frontale, qui sert simultanément de référence acoustique à la correction à champ libre (fig. 5) du côté restitution de l'écouteur (D).
6. Dispositif de filtrage (A2) selon la revendication 4 ou 5, caractérisé par un filtre passif à atténuation de bande (fig. 9) ou par le branchement en chaîne (fig. 4) d'un filtre passe-bande (A10) d'un premier filtre à atténuation de bande (A20) et d'un second filtre à atténuation de bande (A30), le filtre passe-bande (A10) et chacun des filtres à atténuation de bande (A20 ou A30) sont réalisés sous forme de ponts en T avec une impédance d'entrée et de sortie indépendantes de la fréquence.
7. Dispositif de découplage (B) pour exécuter le procédé selon la revendication 1, constitué de deux canaux de micros stéréo et alimentés par la tête d'enregistrement (A) et d'un filtre électrique de découpage (B10), caractérisé en ce qu'une unité de soustraction (B13, resp. B14) est disposée chaque fois dans des branches longitudinales (B11, B12) d'un canal de transmission gauche (Mli, L,) et de droite (Mre, L2) avec une unité de transmission (B15 resp. B16) branchée à la suite, et que, dans des branches transversales qui créent la contre-réaction entre la sortie (L,) du canal de transmission gauche (Mli, L1) et l'entrée négative de l'unité de soustraction (B14) disposée dans la branche longitudinale (B12) du canal de transmission de droite (Mre, L2) ainsi qu'entre la sortie (L2) du canal de transmission de droite (Mre, L2) et l'entrée négative de l'unité de soustraction (B13) disposée dans la branche longitudinale (B11) du canal de transmission de gauche (Mli, L,), est compris chaque fois une unité de contre-réaction (B17, B18), en ce que l'unité de transmission (B15) dans la branche longitudinale (B11) du canal de transmission de gauche (Mli, L,) représente la fonction de transfert à champ libre inverse du canal de micro de gauche (20) pour une des incidences acoustiques latérales (ϕ1, δ1), en ce que l'unité de transmission (B16) dans la branche longitudinale (B12) du canal de transmission de droite (Mre, L2) reproduit la fonction de transfert à champ libre inverse du canal du micro de droite (30) pour l'autre incidence acoustique latérale (ϕ2, δ2), en ce que l'unité de contre-réaction (B18) appliquant la sortie (L2) du canal de transmission de droite (Mre, L2) en contre-réaction reproduit la fonction de transfert à champ libre du canal du micro de gauche (20) pour cette deuxième incidence acoustique (ϕ2, δ2), et en ce que l'unité de contre-réaction (B17) appliquant en contre-réaction la sortie (L,) du canal de transmission de gauche (Mli, L,) reproduit la fonction de transfert à champ libre du canal du micro de droite (30) pour la première incidence acoustique (ϕ1, δ1).
8. Dispositif de découplage selon la revendication 7, caractérisé en ce qu'il comporte dans les canaux de transmission de gauche et de droite (Mli, L, resp. Mre, L2) devant et/ou après le filtre de découplage (B10*) réduit à des parties séparables de sa fonction de transfert totale, d'autres unités de transmission (B61, B71 resp. B62, B72) dont les fonctions de transfert qui contiennent les parties séparées de la fonction de tranfert totale du filtre de découplage (B10) (Fig. 12).
9. Dispositif de découplage selon la revendication 8, caractérisé en ce que les unités de transfert (B61 resp. B62) séparées, disposées avant les unités de soustraction (B13* resp. B14*) du filtre de découplage réduit (B10*) se trouvent dans les canaux de micros (20, 30) pour servir de correcteurs de micros (A2) pour les micros (A1) de la tête d'enregistrement (A).
10. Circuit d'adaptation du signal stéréo (L,, L2) relatif à l'espace à l'écouteur (D) à champ libre corrigé, dans lequel est disposée chaque fois une première unité de transmission (C1) dans les branches longitudinales d'un canal de transmission gauche et droite avant ou après une unité de sommation (C4), et dans lequel un deuxième unité de transmission (C2 resp. C2*) et éventuellement une unité de retard (C3) est disposée chaque fois dans des branches transversales qui couplent de façon additive le canal de transmission de gauche avec celui de droite ainsi que celui de droite avec celui de gauche, pour exécuter le procédé selon la revendication 1, caractérisé
- en ce que la première unité de transmission (C1) disposée devant l'unité de sommation (C4) reproduit la moitié de l'écart de niveau interaulaire de l'ouïe pour l'incidence acoustique de 30° à l'aide d'une chaîne de filtres passe-bandes de deuxième ordre,
- en ce que la deuxième unité de transmission (C2) présente la fonction de transmission inverse de la première unité de transmission (C1) à l'aide d'une chaîne de filtres d'atténuation de bande de deuxième ordre, qui ne se distinguent chaque fois des filtres passe-bandes de la première unité de transmission (C1) que par l'échange de deux résistances (Rx) et (Ry),
- en ce que les fréquences de résonance de tous les filtres passe-bandes et filtres d'atténuation de bande peuvent être adaptées par des impédances capacitives et ohmiques variables (Z) aux fréquences de résonance qui apparaissent dans la courbe de fréquences de l'écart du niveau interaulaire individuel de l'ouïe d'un auditeur déterminé,
- et en ce que des unités de retard variables (C3) formées d'un circuit en chaîne de filtres passe- partout de deuxième ordre sont disposées dans les branches transversales, dont le retard variable en fonction de la fréquence concommitam- ment avec la différence de temps de propagation règlable et fonction de la fréquence par le réglage des fréquences de résonance, de la première et de la deuxième unité de transmission (C1) et (C2) reproduit la différence de retard individuelle en fonction de la fréquence de l'ouïe d'un auditeur déterminé pour l'incidence acoustique de 30° (figs 14, 15 et 16).
11. Circuit (C) d'adaptation du signal stéréo (L,, L2) relatif à l'espace à l'écouteur (D), dans lequel un premier circuit de transmission (C1) est disposé dans les branches longitudinales d'un canal de transmission gauche et droite, et dans lequel chaque fois une deuxième unité de transmission (C2 resp. C2*) et éventuellement une unité de retard (C3) est disposée dans des branches transversales qui couplent de façon additive le canal de transmission de gauche avec celui de droite ainsi que celui de droite avec celui de gauche, pour exécuter le procédé selon la revendication 1, caractérisé en ce que les premières unités de transmission (C1) sont disposées avant le débranchement du signal dans une branche longitudinale et une branche transversale (fig. 17a).
12. Circuit selon la revendication 11, caractérisé
- en ce que les premières unités de transmission (C1) présentent un taux de transmission de 0 dB indépendant de la fréquence dans la gamme de fréquences jusqu'à 15 kHz,
- en ce que les deuxièmes unités de transmission (C2*) reproduisent aussi bien la différence de niveau interaulaire que la différence de retard interaulaire de l'ouïe pour l'incidence acoustique de 30° à l'aide d'un circuit en chaîne de filtres d'atténuation de bande simples de deuxième ordre, chaque filtre d'atténuation de bande pouvant être affecté d'un minimum de phase ou de temps de propagation supplémentaires,
- en ce que chaque filtre d'atténuation de bande de la deuxième unité de transmission (C2*) peut être adapté à la directivité individuelle de l'ouïe d'un auditeur déterminé par trois résistances ohmiques variables,
- et en ce que le circuit simplifié (C) est monté dans un écouteur (D) dont le taux de transmission à champ libre conjointement avec le circuit (C) est indépendant de la fréquence.
EP19800104718 1979-08-09 1980-08-11 Procédé de transmission stéréophonique et moyens pour la mise en oeuvre de ce procédé Expired EP0025509B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT80104718T ATE5458T1 (de) 1979-08-09 1980-08-11 Stereophones uebertragungsverfahren und mittel zur durchfuehrung des verfahrens.

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
DE2932330 1979-08-09
DE19792932330 DE2932330A1 (de) 1979-08-09 1979-08-09 Verfahren und filteranordnung zum stereophonen aufnehmen von schallsignalen mittels eines kunstkopfes
DE2944851 1979-11-07
DE19792944851 DE2944851C2 (de) 1979-11-07 1979-11-07 Anordnung zur Aufnahme stereophoner Tonsignale
DE19803001007 DE3001007C2 (de) 1980-01-12 1980-01-12 Einrichtung zum Aufnehmen stereophoner Signale
DE3001007 1980-01-12
DE19803003852 DE3003852C2 (de) 1980-02-02 1980-02-02 Anordnung zur Aufnahme stereophoner Tonsignale
DE3003852 1980-02-02

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EP0025509A1 EP0025509A1 (fr) 1981-03-25
EP0025509B1 true EP0025509B1 (fr) 1983-11-23

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* Cited by examiner, † Cited by third party
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EP0025509B1 (fr) * 1979-08-09 1983-11-23 Schöne, Peter, Dr.-Ing. Procédé de transmission stéréophonique et moyens pour la mise en oeuvre de ce procédé
DE3102965C2 (de) * 1981-01-29 1983-03-31 Institut für Rundfunktechnik GmbH, 8000 München "Einrichtung zum Aufnehmen und/oder Bearbeiten stereophoner Signale"
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US5173944A (en) * 1992-01-29 1992-12-22 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Head related transfer function pseudo-stereophony

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DE2944851C2 (de) * 1979-11-07 1986-06-12 Kronester, Walter, Dipl.-Ing., 8000 München Anordnung zur Aufnahme stereophoner Tonsignale
DE3001007C2 (de) * 1980-01-12 1984-04-26 Kronester, Walter, Dipl.-Ing., 8000 München Einrichtung zum Aufnehmen stereophoner Signale
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EP0025509B1 (fr) * 1979-08-09 1983-11-23 Schöne, Peter, Dr.-Ing. Procédé de transmission stéréophonique et moyens pour la mise en oeuvre de ce procédé

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EP0025509A1 (fr) 1981-03-25

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