JPH0474918B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for the spatial organization of sound, which may be defined as a "Holophonic" analogous to holography. In particular, the present invention enables the direct recording or conversion of stereophonic sound to provide the listener with a true stereoacoustic dimension that is more spatially effective than two-dimensional sound.

Until now, stereophonic sound has been recorded by placing two or more microphones in the intended locations, and by recording two separate tracks of records or tapes played through two intentionally placed speakers. Made by recording above. Another method is called ``binaural,'' in which an object shaped like a human head is placed between two panoramic microphones to artificially create an acoustic shield to distinguish between the two 3D channels. There is a system. Other extant devices consist of an artificial head with an internal microphone placed at the base of the neck in an attempt to obtain a limited, incomplete sound that can only be experienced through the use of earphones.
Although in the system described above there is a sense that the recorded and played sound is spatial, in reality the system is only a 2-dimensional part of the sound, with a particular tone or instrument coming from the right or left speaker forming its own track. It only provides a sense of dimensionality. This is because, due to the physical laws of hearing, the human ear can be thought of as a system in which stimuli enter and perception exists, and the pinna acts as a collector of sound energy, and the ear canal acts as a collector of sound energy. This is explained by the fact that it is concentrated and delivered to the eardrum in the form of resonant pressure.

As a result of deep exploration and research, the present invention provides an alternative interpretation of the way sound energy is transformed into the auditory organ and, starting from this interpretation, can give a true stereoacoustic perception of the transformed sound. The recording system is revealed.

In order to introduce the holophonic recording mechanism of the device achieved by this invention in an easy-to-understand manner,
The physical and mechanical basic concepts of listening are briefly discussed below. At the same time, the theory for deriving the concept of the system related to this invention will also be explained. Examination of the auditory organ shows that the organ must first parse information from the sound source using its own mechanisms. In animals, the auditory organ is generally organized spatially through the pinna (codific).
The sound information is dynamically analyzed not only through the action (action) but also through the perceptual functions of the entire body. On the other hand, in the most highly evolved humans, with the most complete auditory organs, this organ is capable of instantaneous statistical analysis of sound information, and also allows the listener to immediately know the location of the source of the sound. . Through this invention, it has been discovered that this analysis mechanism is similar to laser holography, that is, sound holography.

As is well known, laser holography consists of a diffraction pattern and a photographic image formed by two laser beams from the same light source (ie, by interference light). One of these is reflected by a mirror and impinges directly on the photographic plate, while the other illuminates the object directly and is then reflected by it. The two rays hit the plate at different angles and paths and interfere with each other. This interference leads to a highly complex pattern of light and dark that contains all the spatial information of the holographic object. Reconstruction of the reflection pattern using a similar method provides the basis for the spatial image of the object. Therefore, when one looks at this spatial image, one has a complete sense of perception that allows one to see not only its original form, that is, its size, but also its size. In order to further clarify the concept of the present invention, a brief discussion of holography in water waves will be provided. When a stone is dropped onto a calm, mirror-like surface of water, several concentric waves are created that expand until they disappear. When these waves encounter obstacles, they reflect back into other waves that interfere with the original waves to form an interference pattern. Although these interferences appear to be turbulent, they contain a stream of information, similar to a hologram. This series of information can thus give the shape of the reflective surface of the obstacle. If the obstruction is symmetrical, it will give a symmetrical interference pattern. However, this pattern gives incomplete information because two images are possible, one is true, and the other is completely similar but
This is because it has been rotated 180°. Therefore, the true location of the wave source cannot be a component of this information.
However, with asymmetric reflective surfaces there is only one spatial reconfiguration possibility. Of course, it will also be clear that the interference pattern is also asymmetric and the exact location of the wave source can then be determined. Note that, as in laser holography, the interference pattern consists of several points, each one of which contains the information of the entire hologram. That is, a reliably programmed computer could reconstruct the entire hologram with the information contained in only one of the points.

The above is the theory on which the present invention is based, and it is based on the lack of functional effects of old stereophonic sound.
In other words, "depth" in formal two-track recording.
It shows the lack of. In fact, when old recordings of this kind are made, one realizes that it is not possible to distinguish between sounds coming from two different points, and the microphone is not sufficient to create an obvious interference pattern. It is also obtained that there is no asymmetry. Therefore, people who listen to old stereo recordings may be able to distinguish between left and right, but not, for example, between top and bottom.

In this way, an asymmetric reflective surface is required to spatially differentiate sounds. The present invention makes it possible to show that the pinna of the human ear is such a surface. The ear is itself a uniquely accomplished synthesis, a work of sublime and extremely precise engineering. Its morphological shape is almost a perfect spiral, and this spiral is a half of the third quadrant before it begins to degenerate.
quadrant). Accordingly, in view of the above discussion, the present invention operates as follows. In other words, the pinna-equivalent part (hereinafter simply referred to as the pinna) of the microphone support, which is shaped like a human head, exhibits complete asymmetry, and in front of a wave source of a specific frequency, both ears and the head of the listener Although interference patterns are essential for spatial analysis, it is the pinna itself that provides the most valuable information. In fact, long vertical directions identify low frequencies (on the order of 1400Hz) through the pinna, while short horizontal directions identify high frequencies above 3400Hz.

The research carried out for this invention also showed that hair (equivalent to a wig) is also of considerable importance in spatial discrimination, and is itself the source of an asymmetric hologram, thereby improving the clear recognition of sounds coming from the front or the rear. It has also become clear that it is possible. In fact, it has been observed that bald people have somewhat reduced front-to-back discrimination along the axis of head symmetry.

Based on these ideas, the holophonic recording system revealed uses an asymmetrical wig to distinguish between front and back, and a cavity that acts like an ear canal, with the correct position and orientation of the eardrum. Not only are there two microphones that are strategically placed and communicate with the cavity that acts like a Eustachian tube behind it, but also the auricle and its interior, which faithfully reproduce the shapes of the auricle, auditory canal, Eustachian tube, and oral cavity. It is characterized by the fact that it contains a microphone device shaped like a human head with a cavity. Here the oral cavity communicates with the outside world. Individually,
The microphone has a thin membrane of cardioid type not smaller than 7 mm. The cavity, which acts like an auditory canal, has a cylindrical shape with an elliptical cross section, and its axis is twisted, and the wall corresponding to the orifice (outer hole) has a front wall that gradually slopes lower toward the front. It consists of a rear wall that becomes higher towards the rear. Preferably, the cavity acting as the auditory canal has an average length along its axis from the orifice to the microphone of 24 mm, with 8 mm on the orifice side being made of the same material as the external auricle and the remaining microphone side. 16 mm has a hard covering layer, fibrocartilage (8 mm) and bony part (16
mm). Naturally, the cords of the two microphones pass through the oral cavity to the outside. Furthermore, in the field of sound recording and reproduction one always tries to use transducers (microphones and loudspeakers) as directly as possible in the frequency range audible to the human ear. Even though today's microphone-amplifier-speaker connections are nearly perfect, when a single sound source (e.g., a violin) is reproduced, the reproduced sound is often quite different from the original sound. It is something.
Most of this difference is not due to microphones, amplifiers, or speakers, but rather to our ears. In fact, even if a microphone faithfully records a sound signal and a speaker faithfully reproduces it, the result will be quite different from what we hear when we listen to a live performance. . This is because microphones do not pick up sound signals in the same way that our listening systems do.

Our two ears, which are the basis of our auditory system, are what enable us to distinguish between the sources of sound. Sound itself (for example, a violin) does not come from a single point, but rather from several concentrated points. Moreover, the room we are in reflects the sound produced by the violin, while also concentrating the sound that our listening system perceives as coming from a space outside the range of the original sound source (in this case the violin). It causes it to occur. The ear easily distinguishes between countless different sound sources, but the microphone lumps them all together. It is clear that this group of sounds that we hear from speakers becomes a single sound source.

Anyone who has recorded a sound signal in an acoustically unsuitable room has found that the effects of that room, including any external noise, are greater when hearing the sound through a microphone than when hearing the sound directly. It's about noticing things that are noticeable. Therefore, in order to record as close to reality as possible, it is very important to have a spatial distinction of this sound through a microphone or the like. Furthermore, a sound signal picked up by a microphone may also be transmitted directly from the source, sometimes in tune and sometimes out of tune, depending on its propagation distance and the signal's own wavelength. It is different from the original sound signal because it is added to the signal. A similar phenomenon becomes even more pronounced where there are several sound sources, such as in the case of an orchestra.

In stereo recording on two separate channels, the quality of the reproduced sound is much higher than that of mono sound. This is because the signals picked up by the left and right microphones are different from each other. By using two appropriately placed speakers and listening to the two signals with the left and right ears, we obtain spatial sound perception. However, this only applies to the front where two speakers are connected at the front. Moreover, this procedure lacks information on height and background.

After years of research and experimentation, it has become clear that in order to reproduce holophonic sounds, it is necessary to restore the human hearing mechanism. In fact, before reaching the eardrum, sound undergoes various delays and deviations from one ear to the other, depending on the source itself. especially
At frequencies above 1000 Hz, these lead to different response curves for different positions of the sound source, and also to phase displacements that create a system of divisions by which the brain can determine the sound source. Let's consider the special shape of the human ear canal -- there are various curves and 2500Hz and
There are two resonant frequencies around 7500Hz. These resonances must be removed during recording, since they already exist in the ear and must be further enhanced by the ear-shaped microphone. For this purpose, suitable filters (either electronic or without electronics, in the latter case they are placed in close proximity to the microphone membrane) are constructed to remove these harmful resonances. It is.

A preferred embodiment of the present invention, which is not particularly limited and is merely an embodiment, will be explained with reference to the following figures. Fig. 1 is a longitudinal cross-sectional view corresponding to the ear canal cavity of the recording mechanism according to the present invention, and Fig. 2 is a cross-sectional view of a portion that acts like the auricle and auditory canal. As shown in the figure, the holophonic recording system includes a microphone support 1 shaped like a human head. This support is preferably made of a plastic material such as polystyrene and holds two ear parts 2 with pinnae 3 faithfully replicating the pinna of the human ear. Each pinna 3
has a cavity 4 having a shape very similar to the auditory canal, and a microphone 5 located at the same position and in the same direction as the tympanic membrane of the ear is placed at the bottom of the cavity 4. The back surface of each microphone 5 directly communicates with a tubular cavity 6 which is faithfully restored to the shape of the Eustachian tube. These cavities 6 faithfully restore the shape of the oral cavity and communicate with a central cavity 7 that communicates with the outside through a tubular cavity 8. The 8 mm portion of the inlet side of the pinna 3 and auditory canal (24 mm long) is preferably made of rubber, while the remaining 16 mm at the back has an internal layer of plaster or 11, respectively, consisting of fibrocartilage and medial. It imitates the bones of the ear. The top is covered with a wig 9 to create a desired asymmetry in the front and back. microphone wire 10
is introduced into the central cavity 7 led out from the tubular cavity 6 and further communicates with the outside through the tubular cavity 8. The so-called "pop" effect found in ordinary microphones (when the sound pressure exceeds a certain predetermined maximum value, the pressure causes a "bong" effect during recording).
In order to eliminate the internal combustion (which causes the diaphragm of the microphone to collapse in such a way as to produce a sound like the internal combustion The auditory canal has a sudden expansion 12 that functions like an engine muffler. The microphone can therefore be exposed to the outside without exhibiting pop effects. Microphon 5 has a cardioid thin film not smaller than 7 mm and is shown as the outer casing of the microphone with an opening of this shape. The cavity 4, which acts like an ear canal, has a cylindrical part with an elliptical cross section, and the axis of the cylinder is twisted, and the wall corresponding to the outer hole is a front wall that gradually slopes lower toward the front. and a rear wall that becomes higher towards the rear. The former is flat and the latter is extremely uneven.

In laser holography, two different rays, one of which is a known ray and the other reflected by an object, interfere with each other, but in holophony, the known sound is It is produced by the reverberation of signals in the anatomy of the individual's body.

In this system, the playback of a magnetic tape recording on an ordinary stereo system allows the listener to conceptually reproduce how the recording was made in the studio, regardless of one's listening sense. In this way, even if the two listeners are facing each other, they will get the before-and-after perception in the correct sense, as if they were side by side. The sound box (used as a recording and/or playback device adapted to allow phase modification so that the phase shift of the harmonics is maintained during recording and playback) must be placed in a predetermined position. It is noteworthy that there is no such thing. This is because those sounds are systematized in advance and the information resulting from them cannot change.

Regarding the perception of pitch, starting from the research of Stephens and Walkman and their diagram showing that frequencies below 500 Hz have a linear relationship with pitch, and then curves, this invention has clarified that Natsuta theory can clarify these studies. In fact, it is known that waves of a certain frequency are reflected only by objects whose physical size is on the order of 1/4 of the wavelength, so the auditory mechanism (ears and head) is irrelevant. Frequencies actually exist. These sounds are thus unchanging and systematized. That is, they are not confirmed to be spatially identical and therefore have a completely linear frequency-height relationship.

The critical dimension measurements for the entire contour of this acoustic system are 20 cm for the head (corresponding to a frequency of 450 Hz) and 6 cm for the ears (corresponding to a frequency of 1400 Hz). If this frequency is exceeded, interference will occur in the vicinity of the ear, resulting in a conflict resulting from cancellation.
Furthermore, as mentioned above, the existence of a spatial system allows the cerebrum to judge the source of the sound that leads to it.
Once the device according to the invention is thus fully analogous to the human hearing mechanism, the full details of the system will be understood.

With this method, regardless of the presence of two ears,
The oscillator reveals that for each spatial location there is a significant change in the response curve of the auditory mechanism and, in addition, there is also a phase shift of the harmonics with respect to the fundamental sound. In fact, measuring the frequency response curve on a human head will match that with the device according to the invention, such that the anatomical characteristics are precisely adhered to in its structure. Various experiments have shown that the curve is traced by sound emanating from one end of a device similar to the average ordinary audiogram known to anyone who studies physiological acoustic effects. It is clearly stated. Furthermore, the curve shows a pronounced drop in frequency and two resonance peaks at 2500 Hz and 7500 Hz, corresponding to the first and third resonant frequencies of the hearing mechanism. front, rear,
Measurements of other characteristic curves by the top and other positions are obtained laterally, those from the front where high temperatures are abundant, especially at the ends, and those from the rear in the bass;
You can see that it's quite different. Therefore, when listening to spatial information it should be considered that some parameters are modified to match the recording. This downside is eliminated by canceling the resonance in a known manner by suitable filters and by using octave amplifiers for higher and lower unknown frequencies. Equalizer (Used to perform amplification by eliminating resonances while removing low and high frequencies in the signal obtained from the use of this equipment, eliminating vibrations that may be present in the frequency response curve and providing a relatively uniform (which provides a frequency response curve with varying degrees of amplification) will provide the listener with the best results.

Regarding the phase displacement of harmonics regarding the fundamental sound,
A sound dynamic analysis constructed using this invention exhibits some high frequency delays, while low frequencies remain stable on the oscillograph.

The phenomenological interpretation is simple and arises from considering the different orientations taken by sounds of different frequencies that make up the sound; - for low frequencies, by some limited wavelength; When the acoustic membrane is exposed to an indeterminate location, the information passes through the body as if it were not there, except in the case of the disappearance of the acoustic membrane, or in the case of the contribution of the skull cavity or internal echo chamber. It is given as it is.

- Higher frequency sounds are unlikely to pass through directly, but sometimes bounce off the ear canal restored in the device, so that their arrival at the microphone placed in the eardrum will not occur simultaneously for all frequencies. . Furthermore, two different spatial locations do not have the same delay. This clearly results in a fully spatially organized symbol being diverse, with the consequence that the loudspeakers must be placed in deliberate positions to avoid large modifications of the original phase displacement. Also, all relevant technical measures are available to respect all phase schemes during the acoustic transformation, i.e. to use a phase-corrected acoustic box or to use a single loudspeaker in extended range form. , should be fully utilized. The device according to the invention with a spatial system of sound clearly
In addition to recording, it is also used for direct transmission of sound.

As described above, according to the sound spatial systemization device of the present invention, two microphones are placed on a microphone support shaped like a human head in the correct position and direction like the eardrum of the ear. The oral cavity's communication with the outside world also allows for the direct recording or transmission of stereophonic sound, giving the listener a spatially true stereoacoustic dimension that is more effective than a two-dimensional sound. You can enjoy the effects.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view corresponding to the ear canal cavity of the recording mechanism according to the present invention, and FIG. 2 is a cross sectional view of the portion that acts like the auricle and the auditory canal. Explanation of symbols, 1...Microphon support, 3
...Auricle, 4,6,7...Cavity, 5...Microphone, 9...Wig, 12...Extension part.

Claims (1)

[Claims] 1. A sound spatial systemization device called a holophonic, similar to holography, capable of recording or directly converting three-dimensional sound in an effective spatial dimension, which comprises an auricle 3, an auditory canal 4, , two microphones 5 arranged in the ear canal 4 in the correct position and direction like the eardrum, and a microphone support 1 shaped like a human head. In the device, the microphon support 1 further includes internal cavities 6 and 7 that are faithfully restored to the shapes of the Eustachian tube and the oral cavity, respectively, and a wig 9 that is asymmetrical to distinguish between the front and the back. Further, each of the microphones 5 communicates with a cavity 6 restored to the shape of a Eustachian tube behind it, and the cavity restored to the shape of an oral cavity communicates with the outside. 2 The cavity 4, which acts like an auditory canal, has a cylindrical shape with an elliptical cross section, and its axis is twisted, and the wall corresponding to the orifice (outer hole) is a front wall that gradually slopes lower toward the front. and a rear wall which becomes higher towards the rear. 3 The cavity 4, which acts like an auditory canal, has an average length of 24 mm along its axis from the orifice to the microphone 5, and 8 mm on the orifice side is made of the same material as the external auricle, and the remaining The 16mm side of the microphone has a covering layer of hard material,
3. A device according to claim 1 or claim 2, each of which simulates fibrocartilage and bone. 4. Claims in which the cavity 4, which acts like an ear canal, has an abrupt expansion 12 to reduce acoustic pressure to eliminate the so-called "hop" effect that can be experienced in a real ear canal. 1st
3. The device according to any one of paragraphs 2 and 3. 5. Using sound boxes or extended range type loudspeakers as recording and/or playback devices adapted to allow phase modification so that the phase shift of the harmonics with respect to the fundamental sound is maintained during recording and playback. 5. A device according to any one of claims 1, 2, 3 and 4, wherein the phase displacement is modified. 6. Claims 1, 2, 3, 4, wherein the equalizer is used to provide a relatively uniform amplification to the frequency response curve to negate all possible changes in that curve. The device according to any one of Items 1 and 5.