FR2638311A1 - ELECTROACOUSTIC METHOD FOR PRESENTING AUDIO SIGNALS FOR THE STEREO SOUND HEARING WITH DIRECTION EFFECT - Google Patents

Abstract

The invention relates to an electroacoustic method of presenting audio signals for directional stereophonic hearing according to the method of binaural reproduction and transmission. It is characterized in that, with a view to the clear perception of the direction of a sound event directed at a listener, there is presented, in addition to the primary signal produced, a second signal, delayed in time, by a sound source L2 located opposite the primary sound source L1 on the line connecting the primary sound source to the listener H, second signal whose delay time with respect to the primary signal is greater than required by the overall auditory localization, but remains smaller than the delay time necessary for the perception of the first echo.

Description

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  The invention relates to an electroacoustic method for pre-

  presentation of audio signals for directional stereophonic hearing according to the binaural reproduction and transmission method. With presently customary reproduction methods with two or more channels, precise directional listening is not possible without ambiguities; the auditor regularly confuses

  o directions come from the sounds.

  Patent AT-345,363 discloses an automatic device

  electroacoustic transmission of sounds, which is uniquely

  form and at the same time faithful as to the direction and distance, in a large local or free space, with sound of a large stage and a large audience, LequeL is spread over a relatively large solid angle around the stage , a device that has several loudspeakers that are at least partly

  at different distances from the sound source and listeners.

  For this purpose, in order to ensure that all listeners are well served without the perception of direction and distance distorted and to produce an increased stereo effect, one or more microphones and / or other signal sources are coordinated each time with areas of sound sources - spatially limited - of the stage and are connected through one or more delay elements and two or more summation circuits free from

  reactions to two or more loudspeakers or loudspeakers

  speakers and / or other speakers distributed in Space, in a temporal coordination such as, for all places

  listeners, the sound, for the same fractions of amplitude,

  the speaker group and the speaker located closest to the Lignere Binder The listener's place and the source area coordinated to the sound source, reaches the listener in question earlier than the sound from the others groups of loudspeakers or other speakers, but later than The original sound. The effect thus obtained is essentially based on the law of the first wavefront, according to which the direction is perceived according to the event

  arriving sound The earliest at the listening point.

  A process which only allows an auditor to perceive the place of sound events situated in front of him has been proposed by J. Blauert in the German patent applications DE-OS 17 62 727

  and 19,665,632; according to this method, to create auditive sensations

  according to desired directions, fractions of the signal

  are given in some frequency bands, so-called direction-determining bands, with respect to others, the effect can be amplified or

  attenuated by realizing, in addition to or instead

  quences presented in a reinforced way, a shift in the time of

  these signal fractions compared to other signal fractions.

  The decisive frequency bands of the listening by the front

  range from 150 Hz to 600 Hz, from 2 kHz to 6.5 kHz and from 16 kHz to 20 kHz.

  This method does provide a certain security in front listening, but it has the disadvantage that it does not take into account the fine structures of the human ear, which also contributes to stamp deformations in many cases. of cases. The causes are the individual characteristics of the auricle and the head, characteristics which, in such a case, are not adapted.

  to the bands determining the direction.

  - German patent application DE-OS No. 20 23 377 also discloses a method, as well as a device for its implementation, for stereophonic reproduction of sound signals by means of loudspeakers. This process ensures the radiation of

  sound signals - recorded as they are actually heard

  with an artificial head - in a breeding

  loudspeakers, so that the impression that the sounds arrive from all sides and the exact directional localization correspond, in a determined part of the listening room,

  those obtained in a specific environment of the local

  tration. This requires the establishment of at least two pairs of

  speakers at the corners adjacent to the base of two iso-triangles

  whose peaks touch each other and whose bases are

  the the. The microphone signals of the artificial heads are sent to this loudspeaker system so that a transmission channel is radiated each time by two speakers diagonally opposite each other, inserted transmission elements causing a phase shift of at least 180 between

  the signals radiated and also taking into account, according to

  angular mutual mutualization of the diagonals loudspeakers, a sound level corresponding to the occultation or sound masking

  variable produced by the head and which is a function of the frequency.

  The diagonal signals arriving at the meeting point of the triangles, that is to say the listening point, are mutually delayed by a time interval At, the delay to be chosen for a given arrangement of the speakers to be calculated according to the following formula :

At = 0.22 the + sinl2 [ms].

  In practice, the angles under which the axes of each time two speakers meet will correspond for e1 to 660 and i

  for e2 to 104, which gives a delay time At of 0.3 ms.

  The processes mentioned are either complex and costly

  or at least limited to a specific application. They remain mostly imperfect, in their practical application, if the audience must be able to detect distinctly and accurately

  the direction in which the site of the events actually

  sound events. In order for this uncertainty in directive listening to no longer occur for the listener in the reproduction and transmission of sounds, the present invention therefore aims to create an electroacoustic method for presenting audio signals.

  for stereophonic hearing with directional effect according to the

  binaural reproduction and transmission, a process which allows, by the simplest means,

  direction effect), without the slightest deformation of the stamp.

  According to the invention, this result is obtained by the

  that, in view of the clear perception of the management of an event,

  sound signal directed to a listener, is presented, in addition to the primary signal produced, a second signal, delayed in time, by a sound source located opposite the primary sound source on the line connecting the primary sound source to the listener, second signal

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  whose delay time with respect to the primary signal is greater than the overall auditory location requires, but remains smaller than the delay time required for perception

of the first echoes.

  The invention is based on the observation that at the audition of a sound event, its direction is indicated spontaneously and without error when there is a return from the opposite direction and following the line connecting the site of the sound event

  and the listener, this referral to arrive at the listening point in the

  the delay mentioned above. At the same time, the return must take place clearly outside the time required for localization.

  global auditory or localization sum. In the stereo reproduction

  reophonique, the particular meaning of the localization sum comes from the fact that the listener perceives a place of listening event which depends on the location of two sound sources and the signals radiated by them. If the differences in level and time of the signals arriving at the listening point are small, the hearing interprets the resulting signals of the ears as if the event came from a single sound source called ghost sound source - located in the area included between the two real sound sources. The delay for both stereo signals must not exceed 1 ms per

  example. When, in accordance with the invention, such a primary signal

  Mayor is presented in a delayed manner as a referral or reflection,

  the listening event gains in spatial extent following the delay.

  However, when one chooses the delay so large that a second listening event occurs distinctly, which will be clearly the case, as a general rule, for delay times greater than ms, the listener perceives the echo . In order for the reference to contribute to the precise determination of the direction, its delay must absolutely be included within the indicated time limits and its direction, to

  from which it is presented, must be contrary to the direc-

  line connecting the primary sound source to the listener.

  The transmission functions of the outer ear, corresponding to the varying incidence directions of the sound, are of particular importance for the listening event perceived by the listener. Recognition of effective direction is possible only if

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  the two ears directly perceive the sound directed towards the listener by the transmission functions of the outer ear corresponding to the direction of incidence of the sound and, on the other hand, the two ears perceive a first echo by the transmission functions of the outer ear corresponding to the direction opposite to that of the line connecting the sound source to

  the listener. Referrals and echoes reaching the ear from

  from other directions than the one mentioned, are evaluated by

  external ear transmission functions which correspond to

  direction and lead to a stereo-

  increased phonics. Although a single referral from the opposite direction guarantees faithful directive listening, it would produce significant deformations of the timbre of the listening event. Therefore, other sound signals are required, reaching the listener especially from lateral directions and whose delay is

  more important than the first referral, to obtain the percep-

  stereophonic and avoid stamp distortion. Therefore, in closed rooms with reflective walls, the usual natural hearing will be preserved; in low reflection rooms, the

  method according to the invention will ensure the clear perception of the direc-

  the sound event arrives at the listener's premises, but the tone of the listening event will be perceived in a distorted way with respect to the natural perception. For this reason, the method according to the invention may also be essential in the simulation of sound incidence directions, or the direction of a place constituting a sound source, because the appropriate matching of mutually corresponding transmission functions of the outer ear allows the listener to recognize certain

predetermined directions.

  In order to support the faithful directive perception of sound sources in large premises, especially sound sources

  changing places on stages or in front of an audience, he

  has just placed several sound sources behind the audience and feed them with the audio signal through a control device so that, if possible for each listener position,

  the condition necessary for listening to the first referral is satis-

  condition that the signal delayed in relation to the primary signal arrives at the place where the listener is, with the appropriate delay, from the direction opposite to that of the

  line connecting the primary sound source to the listener.

  In a practical application of the invention, the transmission method will be implemented using loudspeakers to present to the listener the primary signal and the delayed signal necessary for the clear perception of the direction. The presentation

  using loudspeakers is always

  when the sound of an audience is performed exclusively

  or to improve the conditions of transmission by means of a loudspeaker installation. This is true for all kinds of sound systems, both outdoors and in enclosed spaces, such as in conference and performance rooms, theaters, movie theaters, concert halls, and more. and so on. The important point is that, according to the invention, by means of suitable electroacoustic devices and delay devices, a second time delayed signal is presented, in addition to the primary signal, by a source.

  opposite the line connecting the primary sound source

Mayor to the listener.

  Finally, the process according to the invention can also be used

  in living quarters for stereophonic reproduction.

  According to another practical application of the invention, the primary signal and the delayed signal, necessary for the clear perception of the direction, are presented to the listener by a headset. When listening to sound information recorded on media, for example when listening to music, radio plays, spoken word and so on, which is mainly found on discs and tapes, but also when listening directly to radio broadcasts in stereo, listening through headphones is often preferred over

  by loudspeakers. The process according to the invention is particularly

  advantage in such cases because it allows the listener a clear directional coordination of what he hears, which

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  contributes greatly.to increase pleasure and selectivity

listening.

  The invention will hereinafter be described in more detail in reference

  FIG. 1 shows the principle of the invention and FIG. 2 illustrates the general operation.

for a closed room.

  In FIG. 1, one can see the principle of the invention, according to which an audio signal 4 is presented to a listener H from the left side, for example by a loudspeaker L1, a signal that the listener perceives by the two ears. For the management

  hence the signal is clearly perceived, the listener must receive

  see, in addition to this primary signal, a second signal 5, having the time delay described in the foregoing, of a sound source located opposite the primary sound source, for example L2 speaker. An angular zone, designated t in FIG. 1 and extending about 50 on both sides of the median plane 6, is particularly important for the implementation of the invention. In the practical application, a person P who sings or speaks on a stage for example, as can be seen in FIG. 2, can be acoustically located in a distinct manner,

  in that the same signal 5 'is presented with the temporary delay

  porel necessary from the opposite direction to that of the

  line 4 'connecting the point P of production of the sound and the listener H'.

  However, this signal must be perceived by the listener H 'before the first reflections of the walls 1, 2 and 3 reach it, so that

  that there is no reversal of direction.

Claims (1)

CLAIM   An electroacoustic audio signal presentation method for directional stereophonic hearing using the binaural reproduction and transmission method, characterized   in that, in view of the clear perception of the direction of an event,   In addition to the primary signal produced, a second signal, delayed in time, is presented by a sound source (L2) located opposite the primary sound source (L1) on the connecting line. the primary sound source to the listener (H), the second signal of which. the delay time with respect to the primary signal is greater than the overall auditory location requires, but remains smaller than the delay time   necessary for the perception of the first echo.