JP2021150695A - Stereophonic sound system, recording device, and reproduction device - Google Patents

Abstract

To provide a stereophonic sound system that implements recording and reproduction of stereophonic sound with high presence simply and with a low calculation load.SOLUTION: A stereophonic sound system comprises: a recording unit having 12 microphones arranged three-dimensionally in a sound recording space; and a reproduction unit having 12 speakers arranged three-dimensionally in a sound reproduction space. The reproduction unit reproduces the sound recording space on the basis of a sound signal recorded by the recording unit. A sound recording polyhedron formed by connecting arrangement points of the 12 microphones and a sound reproduction polyhedron formed by connecting arrangement points of the 12 speakers are approximately isomorphic to each other and have a cuboctahedron shape.SELECTED DRAWING: Figure 1

Description

The present invention relates to a stereophonic system, a recording device, and a reproduction device.

Conventionally, the Ambisonics method is known as a method for recording and reproducing three-dimensional stereophonic sound. In Non-Patent Document 1, Ambisonics is a method developed from monophonic to 2-channel stereo, horizontal surround, and three-dimensional sound based on the directional expression of sound incidence, and It is explained that the spherical harmonics were introduced for the expression and reproduction of the three-dimensional sound field. In other words, Ambisonics hierarchically expands the acoustic signals recorded by a plurality of microphones arranged in the acoustic recording space by the spherical harmonics with respect to the incident direction of the wave surface, and based on the obtained spherical harmonics, the acoustics. This is a method of reproducing stereoscopic sound with a plurality of speakers arranged in the reproduction space.

In Patent Document 1, as an example of the ambisonics method, a sound field reproduction system including a sound field reproduction device, a scale model, a sound source, and a speaker, and A format and B format as a sound collection method in an actual sound field, the A format is used. A method using four cardioid microphones arranged at the apex of a regular tetrahedron, or a method using a multi-channel microphone installed on the surface of a sphere. In B format, bidirectionality is provided near the center of the microphone unit. It is disclosed that one microphone is arranged for each of the x, y, and z axis directions and one omnidirectional microphone is arranged.

Further, as a method other than the Ambisonics method, Non-Patent Document 2 describes a 6-channel recording / playback system developed as a subjective evaluation experimental tool for sound. In Non-Patent Document 2, this system is for reproducing a three-dimensional sound field in a laboratory experiment, and six units are combined every 90 degrees to record sound in an actual sound field. A unidirectional microphone is used, as a playback system, 6 speakers are installed in an anechoic chamber to reproduce recorded signals in each direction, and this system can be extended to a general audio recording / playback system. Is described.

JP-A-2019-161455

Akio Ando: Highly Realistic Acoustic Technology and Its Theory, IEICE Fundamentals Review, Vol.3, No.4, pp.33-46 (2010) S. Yokoyama et al .: 6-channel recording / reproduction system for 3-dimensional auralization of sound fields, Acoustical Science and Technology 23, 2, pp.97-103 (2002)

In the Ambisonics method described in Non-Patent Document 1, for the convenience of reproducing stereophonic sound based on spherical harmonics, when reproducing the incident direction of the wave surface with high accuracy, the number of a plurality of microphones in the acoustic recording space is increased. Since it is necessary to increase and densely arrange the stereophonic sound system and to increase the number of a plurality of speakers in the acoustic reproduction space and arrange them densely, there is a problem that the stereophonic sound system becomes complicated and large. Therefore, an increase in the number of microphones and speakers leads to an increase in the calculation load of the spherical harmonics, so it is possible to achieve both recording and reproduction of highly realistic stereophonic sound and a simple and low-calculation stereophonic system. There was a challenge. Furthermore, in the high frequency region, there is also an auditory psychological research result that the perception of stereophonic sound can be explained by parameters such as the interaural time difference, the interaural level difference, and the interaural envelope time difference, and the conventional system is complicated and large. There is a possibility that high-precision wave surface reproduction, which requires conversion, is not necessarily the only means from the viewpoint of recording and reproducing stereophonic sound with a high sense of presence.

On the other hand, in the system described in Non-Patent Document 2, a total of three sets of microphones or speaker pairs of vertices facing each other through the center of a regular octahedron are used to provide orthogonal wave planes in the x, y, and z axis directions in a Cartesian coordinate system. Since the incident direction is constructed and the incident direction of an arbitrary wave surface is expressed by the vector sum, the recorded acoustic signal can be reproduced as it is, so that the calculation load can be easily reduced and the acoustic recording space can be reproduced three-dimensionally. can.

However, in the system described in Non-Patent Document 2, two or more correlations arranged at different positions for the convenience of expressing the incident method of the wave surface by a total of three pairs of microphones or speakers orthogonal to the space. When expressing the sound field radiated from a high-pitched sound source, there is a problem that a sound field different from the actual sound recording space may be reproduced.

The present invention focuses on the above problems, and an object of the present invention is to provide a stereophonic system that can easily record and reproduce stereophonic sound with a high sense of presence with a small calculation load.

The present invention includes a plurality of means for solving the above problems, and an example thereof is as follows.

The three-dimensional sound system of the present invention includes a recording unit in which 12 microphones are three-dimensionally arranged in the sound recording space and a reproduction unit in which twelve speakers are three-dimensionally arranged in the sound reproduction space. It reproduces the acoustic recording space based on the acoustic signal recorded by the unit, and is composed of an acoustic recording polyhedron composed by connecting the arrangement points of 12 microphones and the arrangement points of 12 speakers. The acoustically reproduced polyhedra to be produced are approximately the same type as each other, and their shape is a cubic octahedron.

According to the present invention, since the acoustic recording polyhedron and the acoustic reproduction polyhedron are approximately the same type as each other, the geometrical spatiotemporal information of the acoustic recording polyhedron included in the recorded acoustic signal is the acoustic signal as it is or is insignificant. It can be reproduced in the acoustic reproduction space by performing various corrections and reproducing.

Further, according to the present invention, the incident direction of the wave surface is formed by a total of 6 pairs of microphones or speakers of vertices facing each other through the center of the cube octahedron, and the incident direction of an arbitrary wave surface is expressed by the vector sum. Therefore, it is possible to express the wave surface coming from two sound sources that can be recognized by binaural listening. Therefore, it is possible to easily record and reproduce stereophonic sound with a low calculation load and a high sense of presence.

Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.

It is a schematic block diagram which shows the acoustic recording polyhedron and acoustic reproduction polyhedron of the stereophonic system which concerns on Example 1, and the relationship between them. It is a perspective view which shows an example of the recording apparatus which concerns on Example 1. FIG. It is a schematic block diagram which shows the acoustic reproduction polyhedron which concerns on Example 1 and is formed in the acoustic reproduction space of a rectangular parallelepiped shape. It is a schematic diagram which shows the stereophonic model which concerns on Example 1, and corresponds to the cuboctahedron. It is a schematic diagram which shows the rotational symmetry of the stereophonic system which concerns on Example 1. FIG. It is a schematic diagram which shows the covariance matrix about the rotational symmetry of the 24 × 24 matrix of the acoustic signal in the acoustic recording polyhedron and the acoustic reproduction polyhedron of the stereophonic system which concerns on Example 1. FIG. It is a schematic block diagram which shows the acoustic recording polyhedron and acoustic reproduction polyhedron of the stereophonic system which concerns on Example 2, and the relationship between them. It is a schematic diagram which shows the expression of the large-scale acoustic reproduction space by connecting the acoustic reproduction polyhedron in the stereophonic system which concerns on Example 2. FIG. It is a schematic block diagram which shows the acoustic recording polyhedron and acoustic reproduction polyhedron of the stereophonic system which concerns on Example 3, and the relationship between them. It is a schematic block diagram which shows the acoustic recording polyhedron and acoustic reproduction polyhedron of the stereophonic system which concerns on Example 4, and the relationship between them. FIG. 5 is a schematic configuration diagram showing an acoustic recording polyhedron and a dual acoustic recording polyhedron, an acoustic reproduction polyhedron, and a dual acoustic reproduction polyhedron of the stereophonic system according to the fifth embodiment. 6 is a schematic configuration diagram showing an acoustic recording polyhedron and a dual acoustic recording polyhedron, an acoustic reproduction polyhedron, and a dual acoustic reproduction polyhedron of the stereophonic system according to the sixth embodiment. It is a perspective view which shows the recording apparatus as a specific example of the recording part of FIG. It is a perspective view which shows the reproduction apparatus as a specific example of the reproduction part of FIG. It is a perspective view which shows the acoustic reproduction polyhedron formed in the acoustic reproduction space of the rectangular parallelepiped shape of the stereophonic system which concerns on Example 6. It is a schematic diagram which shows the physical model in the 2D cross section of the acoustic space filled with the rhombic dodecahedron of the stereophonic system which concerns on Example 6. It is an image of the eigenmode which shows the analysis result of the 2D acoustic space using the physical model of the acoustic space by the stereophonic system which concerns on Example 6. It is a schematic block diagram which shows the acoustic recording polyhedron and acoustic reproduction polyhedron of the stereophonic system which concerns on Example 7, and the relationship between them. It is a perspective view which shows the specific example of the speaker enclosure which is a part of the reproduction apparatus of the stereophonic system which concerns on Example 7. FIG. It is a block diagram which shows the conventional stereophonic system by the Ambisonics system. It is a schematic block diagram which shows the acoustic recording polyhedron and acoustic reproduction polyhedron of the conventional stereophonic system which adopts a regular octahedron as an acoustic recording polyhedron and acoustic reproduction polyhedron, and the relationship between them.

The present invention relates to a stereophonic system that records stereophonic sound and reproduces stereophonic sound based on the recorded acoustic signal, and a recording device and a reproducing device used thereto.

In this embodiment, an embodiment of the stereophonic system according to the present invention will be described with reference to the drawings. In each figure, the same reference numerals are given for the same elements, and duplicate description will be omitted.

First, with reference to FIG. 20, the first problem to be solved by the present invention will be described in detail.

FIG. 20 shows a conventional stereophonic system based on the Ambisonics method described in Patent Document 1.

As shown in this figure, in the conventional stereophonic system, first, the acoustic signal 3 recorded by using a plurality of microphones 2 installed in the acoustic recording space 1 is subjected to a spherical harmonic function with respect to the incident direction of the wave surface by the ambisonics encoder 4. The acoustic signal 5 of the Ambisonics system is obtained by developing it hierarchically with. Next, the ambisonics decoder 7 generates a reproduction acoustic signal 8 so that the acoustic signal 3 recorded in the acoustic recording space 1 is reproduced in the acoustic reproduction space 6, and a plurality of speakers 9 installed in the acoustic reproduction space 6 generate the reproduction acoustic signal 8. Reproduce.

In this way, since the ambisonics method expresses the incident direction of the wave surface using the spherical harmonics, the number of the plurality of microphones 2 in the acoustic recording space 1 is increased when reproducing the incident direction of the wave surface with high accuracy. It is necessary to arrange them densely to record the acoustic signal 3 and to increase the number of the plurality of speakers 9 in the acoustic reproduction space 6 to arrange them densely. Therefore, the stereophonic system for recording / reproduction becomes complicated and large, and the calculation load of the spherical harmonics in the ambisonics encoder 4 and the ambisonics decoder 7 increases. For this reason, there is a problem in achieving both the recording and reproduction of 3D sound with a high sense of presence and the simple and low calculation load 3D sound system.

Next, with reference to FIG. 21, the second problem to be solved by the present invention will be described in detail.

FIG. 21 shows a conventional stereophonic system according to the method described in Non-Patent Document 2.

The stereophonic system shown in this figure has a recording unit 10 in which six microphones 2 are three-dimensionally arranged in the sound recording space 1 for recording, and six speakers 9 based on the acoustic signal 3 recorded by the recording unit 10. It is composed of a reproduction unit 12 that is three-dimensionally arranged in the sound reproduction space 6 to reproduce the sound recording space 1. The acoustic recording polyhedron 11 is configured by connecting the arrangement points of the six microphones 2 which are the recording unit 10. The acoustic reproduction polyhedron 13 is configured by connecting the arrangement points of the six speakers 9 which are the reproduction units 12. The acoustic recording polyhedron 11 and the acoustic reproduction polyhedron 13 are approximately the same type 52 as the regular octahedron.

According to this method, the incident directions of the wave planes orthogonal to the X-axis, Y-axis, and Z-axis directions in the Cartesian coordinate system are configured by the pair of the microphones 2 or the speakers 9 which are in a relationship 53 facing each other through the center of the regular octahedron. The incident direction of an arbitrary wave surface is expressed by the vector sum. As a result, by reproducing the recorded acoustic signal as it is, the acoustic recording space 1 can be easily reproduced three-dimensionally with less calculation load. On the other hand, when expressing a sound field radiated from two or more highly correlated sound sources arranged at different positions, there is a possibility that a sound field different from the actual sound recording space 1 may be reproduced. There was a problem that there was.

In view of these problems, the stereophonic system disclosed in the present specification has 12 microphones 2 constituting the recording unit 10 in the sound recording space 1, as shown in FIG. 1 which will be described in detail later as an example. The number of the sound recording polyhedron 11 is geometrically arranged, and the acoustic reproduction polyhedron 13 which is the geometrical arrangement of the speakers 9 constituting the reproduction unit 12 in the acoustic reproduction space 6 is approximately the same type 15. Was devised as a basic idea. Here, the acoustic recording polyhedron 11 and the acoustic reproduction polyhedron 13 are polyhedrons composed of 12 or more vertices, for example, 12 vertices so that the wave planes arriving from two sound sources recognizable by binaural listening can be expressed. It is the same type 15 as the cuboctahedron composed of.

Hereinafter, examples will be described with reference to the drawings.

In addition, in this specification, "isomorphic" means a graphical relation including "congruence" and "similarity" in a mathematical sense. And, "approximately the same type" means that they are generally "the same type". For example, the two corresponding vertices of the two figures have the two in polar coordinates (spherical coordinates) with the center of gravity of the figure as the origin. Even if the angle formed by the coordinate vectors of the vertices is not 0 (zero), it corresponds to "approximately the same type". Here, it is desirable that the angle formed by the coordinate vectors of the two vertices is within 15 degrees. Therefore, when the angle formed by the coordinate vectors of the two vertices is within 15 degrees, it is included in the concept that the two figures are "approximately isomorphic" in the present specification.

Further, the term "general congruence" used in the examples described later also means that it is generally "congruent" in the same manner as the above "general congruence type". In polar coordinates (spherical coordinates) with the center of gravity of the figure as the origin, even if the angle formed by the coordinate vectors of the two vertices is not 0 (zero), it corresponds to "approximate congruence". Here, it is desirable that the angle formed by the coordinate vectors of the two vertices is within 15 degrees. Therefore, when the angle formed by the coordinate vectors of the two vertices is within 15 degrees, it is included in the concept that the two figures are "generally congruent" in the present specification.

FIG. 1 shows the stereophonic system of the first embodiment.

As shown in this figure, the stereophonic system is based on a recording unit 10 in which 12 microphones 2 are three-dimensionally arranged in the sound recording space 1 for recording, and an acoustic signal 3 recorded by the recording unit 10. It is composed of a reproduction unit 12 that reproduces the sound recording space 1 by three-dimensionally arranging the speakers 9 in the sound reproduction space 6. The acoustic recording polyhedron 11 is configured by connecting the arrangement points of the 12 microphones 2 of the recording unit 10. Further, the acoustic reproduction polyhedron 13 is configured by connecting the arrangement points of the 12 speakers 9 of the reproduction unit 12. The acoustic recording polyhedron 11 and the acoustic reproduction polyhedron 13 are approximately the same type 15 as the cuboctahedron.

In this embodiment, the recorded acoustic signal 3 includes spatiotemporal geometric information of the acoustically recorded polyhedron 11 related to the sense of presence. Therefore, when the distortion between the acoustic recording polyhedron 11 and the acoustic reproduction polyhedron 13 is small, the recorded acoustic signal 3 can be reproduced as it is. If the distortion between the sound recording polyhedron 11 and the sound reproduction polyhedron 13 is large, or if the difference in directivity between the microphone 2 and the speaker 9 cannot be ignored, a slight correction related to them can be performed for reproduction. The stereophonic sound of the sound recording space 1 can be easily reproduced in the sound reproduction space 6 with less calculation load. Further, a total of 6 pairs of microphones 2 or speakers 9 having vertices facing each other through the center of the cube octahedron constitute an incident direction of the wave surface, and the vector sum thereof expresses the incident direction of an arbitrary wave surface. Therefore, it is possible to express the wave surface coming from two sound sources that can be recognized by binaural listening.

FIG. 2 shows a recording device as a specific example of the recording unit 10 of FIG.

In FIG. 2, twelve sharply oriented microphones 2 are installed in the microphone holder 17, and each microphone 2 is arranged at the apex of the cuboctahedron. The sound receiving portion of the microphone 2 is installed facing outward. The microphone holder 17 is supported by the microphone stand 16. As a result, the 12 microphones 2 are arranged radially so as to be substantially isomorphic to the cuboctahedron, and the incident of the wave surface reaching the center of the polyhedron can be recorded three-dimensionally.

FIG. 3 shows an acoustic reproduction polyhedron formed in a rectangular parallelepiped acoustic reproduction space.

As shown in this figure, since a normal room (acoustic reproduction space) such as a living room has a rectangular parallelepiped shape, the recorded acoustic signal may be reproduced by the acoustic reproduction polyhedron 13 corresponding to the rectangular parallelepiped shape. be. Even if the shape corresponds to the rectangular parallelepiped shape, it can be said that it is almost the same type as the cuboctahedron. Since the cuboctahedron shown in FIG. 1 is a three-dimensional object in which eight vertices of the cube are cut off to the midpoint of the side, the acoustic reproduction polyhedron 13 is characterized in that it is easy to form a rectangular parallelepiped-shaped chamber.

FIG. 4 shows a stereophonic model corresponding to a cuboctahedron.

In this figure, the close-packed structure is such that 12 spherical acoustic elements 19 are arranged so as to be in contact with the acoustic element core 18 which is the core spherical acoustic element.

When energy is injected into a certain point in the three-dimensional acoustic space, a phenomenon of propagation of acoustic energy due to expansion and compression of the medium occurs around that point. As the minimum component for expressing such an acoustic phenomenon, a spherical acoustic element core 18 is considered as an energy injection point, and a spherical acoustic element 19 is also considered as a propagation target of acoustic energy. The three-dimensional acoustic space is considered to be a homogeneous field in which the acoustic element core 18 and the acoustic element 19 are densely packed.

Then, the arrangement of the acoustic element core 18 and the acoustic element 19 is as shown in this figure. In this case, the geometric structure formed by connecting the centers of gravity of the surrounding acoustic elements 19 is a cuboctahedron.

In this embodiment, the stereophonic system is configured with reference to the cuboctahedron in this way. Therefore, the stereophonic system of this embodiment is associated with a stereophonic model based on geometric thinking.

FIG. 5 is a schematic view showing the rotational symmetry of the stereophonic system according to the present embodiment.

In this figure, the cuboctahedron 20 includes rotation axes 21, 22, and 23 at equilateral triangular faces, square faces, and vertices. The rotating shafts 21, 22, and 23 are typical examples of the shafts. Here, considering the positive and negative directions of the axes, four rotating shafts 21 are provided so as to pass through the center of gravity of the equilateral triangle surface, and three rotating shafts 22 are provided so as to pass through the center of gravity of the square surface. , Six rotation shafts 23 are provided so as to pass through the vertices.

These rotation axes 21, 22, and 23 represent rotation symmetry axes in the acoustic recording polyhedron and the acoustic reproduction polyhedron of the stereophonic system. In the stereophonic system of this embodiment, it is possible to perform calculations using the rotational symmetry of the cube octahedron.

The cubic octahedron has eight types of rotations every 120 degrees (T ₁ , T ₁ ² , T ₂ , T ₂ ² , T ₃ , T ₃ ² , T ₄ , T ₄ ² ) that pass through the center of gravity of the equilateral triangle surface. _{9 types of rotation every 90 degrees (S 1} , S ₁ ² , S ₂ , S ₂ ² , S ₃ , S ₃ ² , S ₄ , S ₄ ² ) that pass through the center of gravity of a square surface, every 180 degrees that pass through the apex It has 8 + 9 + 6 + 1 = 24 types of rotational symmetry transformations, which is the sum of the 6 types of rotations (V ₁ , V ₂ , V ₃ , V ₄ , V ₅ , V _{6) and the equilateral transformation I.}

As an example of the operation using this rotational symmetry transformation, first, three-dimensional panning is given. Here, this method using the rotation transformation group is called the GBAP method (Group Base Amplitude Panning).

The acoustic signal 3 recorded by the recording unit 10 of the cuboctahedron shown in FIG. 2 is represented by the following matrix (formula (1)).

Here, each row corresponds to the acoustic signal 3 recorded by the 12 microphones 2, and the column length n corresponds to the number of time samples, so that the matrix X is a 12 × n matrix. Become. _{Now, when one of the rotations T 1} every 120 degrees passing through the center of gravity of the surface of an equilateral triangle is applied to the matrix X, for example, in the matrix, the elements of the row rotate as expressed by the following equation (2). It becomes a form replaced according to.

Therefore, in the GBAP method, the virtual stereoscopic angle φ [rad] and the maximum stereoscopic angle φ ₀ = π / 3 [rad] are set based on the intermediate angle of 60 degrees (= π / 3 [rad]) of rotation of 120 degrees. When determined, the gain w _T1 of the gain matrix X w _I and T ₁ (X), for example in accordance with sign rule, comes to have a relationship expressed by the following equation (3).

Alternatively, similarly, according to Tangent's law, the relationship represented by the following equation (4) is obtained.

With any of these, as a natural extension of amplitude panning, it is possible to realize various three-dimensional panning by 24 kinds of rotational symmetry transformations.

Next, as another example of the calculation using the rotational symmetry transformation, a covariance matrix relating to the rotational symmetry of the recorded acoustic signal 3 will be given.

Usually, the covariance matrix calculates the covariance between the acoustic signals 3 recorded by each microphone 2, and uses the result for, for example, analysis of the acoustic recording space and correction of the acoustic reproduction space. However, its meaning is statistical and difficult to physically interpret.

On the other hand, in the stereophonic system of this embodiment, it is possible to introduce a geometric interpretation to the value of the covariance matrix by using rotational symmetry. That is, when the covariance matrix calculation is performed after converting each of the matrices X of the 24 types of acoustic signals 3 that have undergone 24 types of rotational symmetry transformations into one-dimensional vectors, the same about the rotational symmetry of the 24 × 24 matrix is performed. Get the covariance matrix.

FIG. 6 is a simplified representation of the covariance matrix with respect to the rotational symmetry of the 24 × 24 matrix.

As shown in this figure, each element of the matrix has a uniform transformation type 1 24, a rotation every 120 degrees 25 that passes through the center of gravity of an equilateral triangle surface, and a rotation every 90 degrees 9 that passes through the center of gravity of a square surface. It shows the dispersion relation of 24 kinds of rotational symmetry transformations of kind 26 and 6 kinds 27 rotating every 180 degrees passing through the apex. From this, a geometrical interpretation of 24 types x 24 types of rotational symmetry can be obtained.

As a result, as shown in FIG. 3, when the sound reproduction polyhedron 13 configured in the sound reproduction space 6 is distorted with respect to the cubic octahedron, or the difference in directivity between the microphone 2 and the speaker 9 Is not negligible, for example, the covariance matrix for rotational symmetry obtained in the acoustic reproduction space 6 is geometrically matched with the covariance matrix for rotational symmetry obtained in the acoustic recording space 1. By applying a scientific correction, it is possible to reproduce a sound field with a high sense of presence.

Although the rotational symmetry transformation has been described here as a symmetric operation, in the stereoscopic sound system of this embodiment, for example, as shown in FIG. 5, the rotation axis 21 passing through the center of gravity of a regular triangle and the center of gravity of a square surface pass through. A reflection symmetry transformation can also be utilized by the reflection surface 352, which is a plane including the rotation axis 22. This makes it possible to express sound reflections, and by calculating the covariance matrix for reflection symmetry, a geometric interpretation of spatial sound reflections can be obtained.

FIG. 7 shows the stereophonic system of the second embodiment.

As shown in this figure, the stereophonic system is based on a recording unit 10 in which 14 microphones 2 are three-dimensionally arranged in the sound recording space 1 for recording, and an acoustic signal 3 recorded by the recording unit 10. It is composed of a reproduction unit 12 that reproduces the sound recording space 1 by three-dimensionally arranging the speakers 9 in the sound reproduction space 6. The acoustic recording polyhedron 11 is configured by connecting the arrangement points of the 14 microphones 2 of the recording unit 10. Further, the acoustic reproduction polyhedron 13 is configured by connecting the arrangement points of the 14 speakers 9 of the reproduction unit 12. The acoustic recording polyhedron 11 and the acoustic reproduction polyhedron 13 are approximately the same type 28 as the rhombic dodecahedron.

In this embodiment, a total of seven pairs of microphones 2 or speakers 9 of vertices facing each other through the center of the rhombic dodecahedron constitute the incident direction of the wave surface, and the vector sum of the pair constitutes the incident direction of an arbitrary wave surface. Express. Therefore, it is possible to provide the expressive power of the wave surface by adding one set to the six sets having the minimum configuration for expressing the wave surface coming from the two sound sources that can be recognized by binaural listening.

Since the rhombic dodecahedron is a dual polyhedron with the center of gravity of the equilateral triangle and square faces of the cuboctahedron as new vertices, 24 types of rotational symmetry conversions are performed in the same manner as the cubic polyhedron. Have.

Further, the rhombic dodecahedron has a feature that it can fill a three-dimensional space by itself.

FIG. 8 shows a state in which a three-dimensional space is filled with a rhombic dodecahedron.

As shown in this figure, assuming an acoustic reproduction polyhedron 13 that is approximately the same type as the rhombic dodecahedron in the acoustic reproduction space 6, 12 acoustic reproduction polyhedra 113 that have moved in parallel are connected to the surroundings to produce acoustics. The reproduction space 6 can be filled without any gaps. As a result, when the listener reproduces the sound field when physically or virtually moving from the acoustic reproduction polyhedron 13 to the acoustic reproduction polyhedron 113 connected to the surroundings, smooth connection between the polyhedra is possible. Therefore, a large-scale acoustic reproduction space 6 can be reproduced.

FIG. 9 shows the stereophonic system of Example 3.

As shown in this figure, the stereophonic system is based on a recording unit 10 in which 20 microphones 2 are three-dimensionally arranged in the sound recording space 1 for recording, and an acoustic signal 3 recorded by the recording unit 10. It is composed of a reproduction unit 12 that reproduces the sound recording space 1 by three-dimensionally arranging the speakers 9 in the sound reproduction space 6. The acoustic recording polyhedron 11 is configured by connecting the arrangement points of the 20 microphones 2 of the recording unit 10. Further, the acoustic reproduction polyhedron 13 is configured by connecting the arrangement points of the 20 speakers 9 of the reproduction unit 12. The acoustic recording polyhedron 11 and the acoustic reproduction polyhedron 13 are approximately the same type 29 as the regular dodecahedron.

In this embodiment, a total of 10 pairs of microphones 2 or speakers 9 of vertices facing each other through the center of the regular dodecahedron constitute the incident direction of the wave surface, and the vector sum of the pair constitutes the incident direction of an arbitrary wave surface. In order to express it, it is possible to provide the expressive power of the wave surface by adding 4 sets to the 6 sets having the minimum configuration for expressing the wave surface coming from two sound sources that can be recognized by binaural listening.

With respect to rotational symmetry, the stereophonic system of the present invention has 20 types of rotation every 120 degrees through the apex, 24 types of rotation every 72 degrees through the center of gravity of a regular pentagonal surface, and every 180 degrees through the midpoint of a side. It has 20 + 24 + 15 + 1 = 60 kinds of rotational symmetry transformations, which is the sum of 15 rotations and the uniform transformation I.

Therefore, compared to Example 1 having 24 kinds of rotational symmetry transformations, this example having 60 kinds of rotational symmetry transformations includes three-dimensional panning by the GBAP method, calculation of a covariance matrix related to rotational symmetry transformations, and the calculation thereof. The analysis enables the expression of more sophisticated and complex stereoscopic sound.

FIG. 10 shows the stereophonic system of Example 4.

As shown in this figure, the stereophonic system is based on a recording unit 10 in which 12 microphones 2 are three-dimensionally arranged in the sound recording space 1 for recording, and an acoustic signal 3 recorded by the recording unit 10. It is composed of a reproduction unit 12 that reproduces the sound recording space 1 by three-dimensionally arranging the speakers 9 in the sound reproduction space 6. The acoustic recording polyhedron 11 is configured by connecting the arrangement points of the 12 microphones 2 of the recording unit 10. Further, the acoustic reproduction polyhedron 13 is configured by connecting the arrangement points of the 12 speakers 9 of the reproduction unit 12. The acoustic recording polyhedron 11 and the acoustic reproduction polyhedron 13 are approximately the same type 30 as the regular icosahedron.

In this embodiment, a total of 6 pairs of microphones 2 or speakers 9 of vertices facing each other through the center of the regular icosahedron form an incident direction of the wave surface, and the vector sum of the pair constitutes the incident direction of an arbitrary wave surface. In order to express, it is possible to provide the expressive power to express the wave surface coming from two sound sources that can be recognized by binaural listening.

Since the regular icosahedron is a dual polyhedron with the center of gravity of the regular pentagonal face of the regular icosahedron as a new vertex, 60 types of rotational symmetry conversions are performed in the same manner as the regular icosahedron. Has. Therefore, as compared with Example 1 having 24 kinds of rotational symmetry transformations, three-dimensional panning by a more diverse GBAP method, calculation of a covariance matrix related to rotational symmetry transformations, and analysis thereof are realized.

FIG. 11 shows the stereophonic system of Example 5.

As shown in this figure, the three-dimensional sound system includes a recording unit 10 in which six microphones 2 and eight dual microphones 32 (14 microphones in total) are three-dimensionally arranged in the sound recording space 1 for recording. It is composed of a reproduction unit 12 that reproduces the sound recording space 1 by three-dimensionally arranging six speakers 9 and eight dual speakers 35 (14 speakers in total) in the sound reproduction space 6.

By connecting the arrangement points of the six microphones 2 of the recording unit 10, the acoustic recording polyhedron 11 which is a regular octahedron is configured. It is a cube by connecting those that touch each other with respect to the arrangement points of the dual microphones 32 arranged at the center of gravity 31 of the surface of the sound recording polyhedron 11 (including the points on the normal line passing through the center of gravity 31 on the surface). The dual sound recording polyhedron 33 is configured.

By connecting the arrangement points of the six speakers 9 of the reproduction unit 12, the acoustic reproduction polyhedron 13 which is a regular octahedron is configured. It is a cube by connecting those that touch each other with respect to the arrangement points of the dual speakers 35 arranged at the center of gravity 34 of the surface of the acoustic reproduction polyhedron 13 (including the points on the normal line passing through the center of gravity 34 on the surface). A dual acoustic reproduction polyhedron 36 is configured. The acoustic recording polyhedron 11 and the acoustic reproduction polyhedron 13 are approximately the same type 14. The dual sound recording polyhedron 33 and the dual sound reproduction polyhedron 36 are approximately the same type 14.

In other words:

The acoustic recording polyhedron 11 formed by connecting the arrangement points of the six microphones 2 and the acoustic reproduction polyhedron 13 formed by connecting the arrangement points of the six speakers 9 are substantially isomorphic to each other, and their shapes are substantially the same. It is a regular octahedron. The dual sound recording polyhedron 33 formed by connecting the arrangement points of the eight dual microphones 32 and the dual sound reproduction polyhedron 36 formed by connecting the arrangement points of the eight dual speakers 35 are substantially isomorphic to each other. And its shape is a cube. The cube is dual with the octahedron, which has an approximately isomorphic relationship with the octahedron.

Here, a dual polyhedron, which is a polyhedron having a dual relationship with a certain polyhedron (for example, the sound recording polyhedron 11) (dual sound recording polyhedron 33), is in contact with a polyhedron with the center of gravity of the surface as a new apex. A polyhedron formed by connecting the centers of gravity of faces with sides and using a polygon that connects the centers of gravity of the faces that touch at the apex as faces.

The sound recording polyhedron 11 and the dual sound recording polyhedron 33 are in contact with each other at the sides. Further, the acoustic reproduction polyhedron 13 and the dual acoustic reproduction polyhedron 36 are in contact with each other at the sides.

The stereophonic system shown in this figure constitutes an acoustic recording space 1 and an acoustic reproduction space 6 by a regular octahedron and a cube which is a dual polyhedron thereof. Therefore, a total of 7 pairs of microphones or speakers, 3 pairs of vertices facing each other through the center of the octahedron and 4 pairs of vertices facing each other through the center of the cube, constitute the incident direction of the wave plane, and the vector thereof. The incident direction of an arbitrary wave surface is expressed by the sum. Therefore, it is possible to provide the expressive power of the wave surface by adding one set to the six sets having the minimum configuration for expressing the wave surface coming from the two sound sources that can be recognized by binaural listening.

Also, by using the dual polyhedron as a reference, the dual relationship behind the acoustic phenomenon, that is, the elasticity associated with the compression and expansion of the medium in the acoustic phenomenon, and the duality of the inertia associated with the motion of the medium are physically related. It enables recording and reproduction in an interpretable form.

FIG. 12 shows the stereophonic system of Example 6.

As shown in this figure, in the stereophonic system, 26 microphones 2 are three-dimensionally arranged in the sound recording space 1 for recording, and 26 speakers 9 are three-dimensionally arranged in the sound reproduction space 6. It is composed of a reproduction unit 12 for reproducing the sound recording space 1.

By connecting the arrangement points of the 12 microphones 2 of the recording unit 10, the acoustic recording polyhedron 11 which is a cuboctahedron is configured. A cubic octahedron by connecting those that touch each other with respect to the arrangement points of the dual microphones 32 arranged at the center of gravity 31 of the surface of the acoustic recording polyhedron 11 (including the points on the normal line passing through the center of gravity 31 on the surface). The dual sound recording polyhedron 33, which is a dual polyhedron of the above, is configured.

The acoustic reproduction polyhedron 13 is configured by connecting the arrangement points of the 14 speakers 9 of the reproduction unit 12. Acoustic reproduction With respect to the arrangement points of the dual speakers 35 arranged at the center of gravity 34 of the surface of the polyhedron 13 (including the points on the normal line passing through the center of gravity 34 on the surface), the dual acoustic reproduction is performed by connecting the objects in contact with each other at the sides. The polyhedron 36 is configured. The acoustic recording polyhedron 11 and the acoustic reproduction polyhedron 13 are approximately the same type 37. The dual sound recording polyhedron 33 and the dual sound reproduction polyhedron 36 are approximately the same type 37.

The rhombic dodecahedron shown in this figure is a spherical rhombic dodecahedron whose vertices are arranged on a spherical surface 38 having the same radius from the acoustic center.

FIG. 13 shows a recording device as a specific example of the recording unit 10 of FIG.

In FIG. 13, twelve sharply oriented microphones 2 are installed in the microphone holder 17, and each microphone 2 is arranged at the apex of the cuboctahedron. The sound receiving portion of the microphone 2 is installed facing outward. The microphone holder 17 is supported by the microphone stand 16.

Further, 14 sharply directional dual microphones 32 are installed in the microphone holder 17, and each dual microphone 32 is arranged at the apex of the rhombic dodecahedron. The sound receiving portion of the dual microphone 32 is installed facing outward. The microphone holder 17 is supported by the microphone stand 16.

This allows the incident of the wave plane arriving at the center of the polyhedron to be recorded in a physically interpretable form with respect to the duality behind the acoustic phenomenon.

An omnidirectional microphone 39 may be provided at the center of the sound for the purpose of evaluating the absolute sound pressure of the sound field to be recorded. As a result, the absolute sound pressure is captured by the omnidirectional microphone 39, and the acoustic signal 3 recorded by the surrounding acoustic recording polyhedron 11 and the dual acoustic recording polyhedron 33 shown in FIG. Since it is possible to evaluate the relationship, it can be used for noise countermeasures, design, etc., which require absolute sound pressure evaluation of the sound field.

FIG. 14 shows a reproduction device as a specific example of the reproduction unit 12 of FIG.

In FIG. 14, 12 speakers 9 are arranged on the speaker stand 40 so as to be substantially the same type as the cuboctahedron, and 14 dual speakers 35 are arranged so as to be approximately the same type as the rhombic dodecahedron. ing.

As a result, the acoustic signal 3 recorded by the recording unit 10 of FIG. 13 can be reproduced as it is, or can be reproduced by performing an operation by the GBAP method or the like, so that the calculation load is easily reduced and the stereophonic sound of the acoustic recording space 1 is reproduced. Can be reproduced in the acoustic reproduction space 6.

FIG. 15 shows an acoustic reproduction polyhedron formed in a rectangular parallelepiped acoustic reproduction space.

As shown in this figure, since a normal room (acoustic reproduction space) such as a living room has a rectangular parallelepiped shape, the recorded acoustic signals are the acoustic reproduction polyhedron 13 and the dual acoustic reproduction polyhedron 36 corresponding to the rectangular parallelepiped shape. May be reproduced by. Even if the shape corresponds to the rectangular parallelepiped shape, it can be said that it is almost the same type as the cuboctahedron and the rhombic dodecahedron. A cube octahedron is a solid in which eight vertices of the cube are cut off to the midpoint of the side, and a rhombic dodecahedral is approximately the same type as a solid that connects the eight vertices of a rectangular parallelepiped and the centers of gravity of the six faces. The sound reproduction polyhedron 13 is characterized in that it is easy to form a rectangular parallelepiped chamber.

Regarding the distortion of the acoustic reproduction space 6 due to the formation of the rectangular chamber, for example, the covariance matrix related to the rotational symmetry as shown in FIG. 6 is calculated in the acoustic recording space 1 and the acoustic reproduction space 6, respectively. , There are methods such as correcting the acoustic signal so that the two match.

Further, the stereophonic system of this embodiment is also characterized in that it corresponds to a physical model of stereophonic sound based on the dual relationship between elasticity and inertia.

FIG. 16 shows a physical model representation of an acoustic space filled with a rhombic dodecahedron in a two-dimensional cross section.

In this figure, the acoustic compliance 42 represented as a spring extends from the elastic center 41 in 6 of 12 directions (including those not shown because it is a two-dimensional cross section) in total. ing. An acoustic inertia 43 represented as a center of inertia is arranged between the springs. That is, the polyhedron connecting the elastic centers is the cuboctahedron 20, and the polyhedron with the inertial center as the face is the rhombic dodecahedron 152. Therefore, the cuboctahedron 20 and its dual polyhedron rhombic dodecahedron 152 are associated with a physical model of stereophonic sound.

Since this model is a physical model, acoustic calculations are possible. For the sake of simplicity, only two-dimensional waves will be mentioned here.

As shown in this figure, the coordinate system for acoustic calculation takes three axes of _{x 1} , x ₂ , and x _{3 rotated by 120 degrees.}

First, consider the mass conservation law for the region V surrounded by the closed curved surface S of the cell that fills the space (hexagon in the case of two dimensions, rhombic dodecahedron in the case of three dimensions). At a certain time, the mass contained in V is expressed by the following equation (5).

Here, δ is the diameter of the acoustic element, and ρ is the density of air.

Therefore, the mass change per unit volume is expressed by the following equation (6).

This mass change occurs as sound waves flow through surface S into region V. Now consider the mass flowing out through the area element dS of the surface S. It is ρ v _n dS per unit volume. However, v _n is the directional component of the outward normal of the particle velocity v with respect to the surface S, and in the two-dimensional model of FIG. 16, a total of three axis components are considered. The total outflow amount is expressed by the following equation (7).

Here, the following relational expression (8) was used for the surface element of a regular hexagon.

Therefore, from the above equations (6) and (7), the continuity equation (9) expressed as follows is obtained.

Next, consider the equation of motion. As shown in FIG. 16, the motion of the acoustic inertia 43, which is the center of inertia on _{each axis x 1} , x ₂ , x _{3, is considered as one dimension.} Therefore, the equation of motion is given by the following equation (10) as in the case of one dimension.

Further, the continuity equation (9) and the equation of motion (10) are discretized for numerical analysis. The variable names as shown in FIG. 16 are given with the elastic center 41 as the sound pressure reference point and the acoustic inertia 43 as the inertial center as the particle velocity reference point. The gradient of the particle velocity in the above continuity equation (9) is discretized by the Euler method as in the following equation (11).

By substituting the above equation (11) into the above continuity equation (9) and rearranging it, the following discretized continuity equation (12) is obtained.

Further, the gradient of the sound pressure in the above equation of motion (10) is discretized as in the following equation (13).

When the above equation (13) organized by substituting the above equation of motion (10), we obtain the following equation (14) with respect to example x ₁ axial direction.

Finally, the following state-space equation (15) is obtained from the above equation (12) and the above equation (14).

The matrix of the first term of the above equation represents the energy storage characteristics in elasticity and inertia, and the matrix of the first term on the right side represents the connection of elastic and inertial elements.

As an example of numerical analysis, consider a two-dimensional rectangular acoustic space represented by the following equation (16).

Assuming that the boundary is rigid (particle velocity is zero), the above-mentioned equation (15) formulated is combined to obtain the target state-space equation. The vertical and horizontal directions were divided into 25 parts, and a total of 625 elements were used for the calculation.

FIG. 17 shows the eigenvalue analysis of the state space equation obtained from the above equation (15), and the eigenmode and the natural frequency of the obtained acoustic space, respectively.

In this figure, white indicates the sound pressure node, and black indicates the sound pressure antinode. For example, (1,0) in the figure is unique in that there is one node in the horizontal direction and zero node in the vertical direction. It shows vibration. In the figure, Sim shows the exact solution of the natural frequency obtained by this model, and Exact shows the exact solution of the natural frequency in the rectangular chamber of _{l x} × l _y. This exact solution is expressed by the following equation (17).

However, n _x , n _y are all 0,1,2,3 ...

From this result, it can be seen that the analysis result by the model and the exact solution agree with each other with an error of up to 2.3%.

From the above, it was demonstrated that acoustic analysis can be performed based on the geometrical configuration of the stereophonic system according to this example.

FIG. 18 shows the stereophonic system of Example 7.

In the stereophonic system shown in this figure, the sound recording space 1 and the sound reproduction space 6 are the same space, and the sound recording polyhedron 11 and the sound reproduction polyhedron 13 are approximately 44 in total. Therefore, the recording unit 10 and the reproducing unit 12 are fused to form a stereophonic system, and the acoustic signal 3 recorded by the recording unit 10 is subjected to operations 45 such as rotation operation, reverberation addition, and filtering such as sound pressure reduction. By reproducing the generated acoustic signal in the reproduction unit 12, it is possible to construct an interactive stereophonic system and provide a creative sound field.

FIG. 19 shows a part of a reproduction device as a specific example of the recording unit 10 and the reproduction unit 12 of FIG.

FIG. 19 shows a state in which the speaker enclosure 46, which is a part of the reproduction device, is installed at the apex 252 of the rectangular parallelepiped chamber. The speaker enclosure 46 is provided with a microphone 2 in the vicinity of the speaker unit 50 so that the sound recording polyhedron 11 and the sound reproduction polyhedron 13 are approximately congruent.

The speaker enclosure 46 has a triangular pyramid shape and is in contact with the wall A (47), the wall B (48), and the wall C (49).

This makes it possible to provide a stereophonic system having a device configuration in which the recording unit and the reproduction unit are compactly housed.

Regarding the low frequency characteristics as a speaker, an opening 51 is provided near three sides composed of wall A (47), wall B (48) and wall C (49), and a horn type that utilizes space is adopted. May be good. Further, a passive radiator type low frequency compensation circuit may be provided.

Further, by providing a light source in the space and using the opening 51 as a light passage, the space may also have a function as indirect lighting. This makes it possible to construct an interactive stereophonic system using sound waves and light.

1: Sound recording space, 2: Microphone, 3: Sound signal, 4: Ambisonics encoder, 5: Ambisonics type sound signal, 6: Sound reproduction space, 7: Ambisonics decoder, 8: Reproduced sound signal, 9: Speaker, 10: Recording part, 11: Sound recording polyhedron, 12: Reproduction part, 13: Sound reproduction polyhedron, 14, 15, 28, 29, 30, 37, 52: Approximate type, 16: Microphone stand, 17: Microphone holder , 18: Acoustic element core, 19: Acoustic element, 20: Cubic octahedron, 21, 22, 23: Rotation axis, 24: Constant conversion 1 type, 25: Rotation 8 types, 26: Rotation 9 types, 27: Rotation 6 types, 31, 34: Center of gravity, 32: Dual microphone, 33: Dual acoustic recording polyhedron, 35: Dual speaker, 36: Dual acoustic reproduction polyhedron, 38: Spherical surface with the same radius from the acoustic center, 39: Omnidirectional microphone, 40: Speaker stand, 41: Elastic center, 42: Acoustic compliance, 43: Acoustic inertia, 44: Approximate congruence, 45: Operation, 46: Speaker enclosure, 47: Wall A, 48: Wall B, 49: Wall C, 50 : Speaker unit, 51: Opening, 53: Opposing relationship through the center, 152: Rhombus zodiac, 252: Top of the room, 352: Mirror surface.

Claims (12)

A recording unit in which 12 microphones are arranged three-dimensionally in the acoustic recording space,
It is equipped with a reproduction unit in which 12 speakers are arranged three-dimensionally in the acoustic reproduction space.
The reproduction unit reproduces the acoustic recording space based on the acoustic signal recorded by the recording unit.
The acoustic recording polyhedron formed by connecting the arrangement points of the 12 microphones and the acoustic reproduction polyhedron formed by connecting the arrangement points of the 12 speakers are approximately the same type as each other, and their shapes are cubic octahedrons. A stereophonic system that is a polyhedron. A recording unit in which 14 microphones are arranged three-dimensionally in the acoustic recording space,
It is equipped with a reproduction unit in which 14 speakers are arranged three-dimensionally in the acoustic reproduction space.
The reproduction unit reproduces the acoustic recording space based on the acoustic signal recorded by the recording unit.
The acoustic recording polyhedron formed by connecting the arrangement points of the 14 microphones and the acoustic reproduction polyhedron formed by connecting the arrangement points of the 14 speakers are approximately the same type as each other, and the shape thereof is rhombic dodecahedron. A three-dimensional sound system that is a dihedron. A recording unit in which 20 microphones are arranged three-dimensionally in the acoustic recording space,
It is equipped with a reproduction unit in which 20 speakers are arranged three-dimensionally in the acoustic reproduction space.
The reproduction unit reproduces the acoustic recording space based on the acoustic signal recorded by the recording unit.
The acoustic recording polyhedron formed by connecting the arrangement points of the 20 microphones and the acoustic reproduction polyhedron formed by connecting the arrangement points of the 20 speakers are approximately the same type as each other, and their shapes are regular dodecahedron. A three-dimensional sound system that is a polyhedron. A recording unit in which 12 microphones are arranged three-dimensionally in the acoustic recording space,
It is equipped with a reproduction unit in which 12 speakers are arranged three-dimensionally in the acoustic reproduction space.
The reproduction unit reproduces the acoustic recording space based on the acoustic signal recorded by the recording unit.
The acoustic recording polyhedron formed by connecting the arrangement points of the 12 microphones and the acoustic reproduction polyhedron formed by connecting the arrangement points of the 12 speakers are approximately the same type as each other, and their shapes are regular icosahedron. A stereophonic system that is an icosahedron. A recording unit in which 6 microphones and 8 dual microphones are arranged three-dimensionally in the acoustic recording space, and
It is equipped with a reproduction unit in which 6 speakers and 8 dual speakers are three-dimensionally arranged in an acoustic reproduction space.
The reproduction unit reproduces the acoustic recording space based on the acoustic signal recorded by the recording unit.
The acoustic recording polyhedron formed by connecting the arrangement points of the six microphones and the acoustic reproduction polyhedron formed by connecting the arrangement points of the six speakers are substantially isomorphic to each other, and their shapes are regular octahedrons. And
The dual sound recording polyhedron formed by connecting the arrangement points of the eight dual microphones and the dual sound reproduction polyhedron formed by connecting the arrangement points of the eight dual speakers are substantially isomorphic to each other. The shape is a cube,
The cube is a stereophonic system that is dual to the octahedron, which has a substantially isomorphic relationship with the octahedron. A recording unit in which 12 microphones and 14 dual microphones are three-dimensionally arranged in the acoustic recording space, and
It is equipped with a reproduction unit in which 12 speakers and 14 dual speakers are three-dimensionally arranged in an acoustic reproduction space.
The reproduction unit reproduces the acoustic recording space based on the acoustic signal recorded by the recording unit.
The acoustic recording polyhedron formed by connecting the arrangement points of the 12 microphones and the acoustic reproduction polyhedron formed by connecting the arrangement points of the 12 speakers are approximately the same type as each other, and their shapes are cubic octahedrons. It is a polyhedron
The dual sound recording polyhedron formed by connecting the arrangement points of the 14 dual microphones and the dual sound reproduction polyhedron formed by connecting the arrangement points of the 14 dual speakers are substantially isomorphic to each other. The shape is a rhombic dodecahedron,
The rhombic dodecahedron is a stereophonic system that is dual to the cuboctahedron, which has a roughly similar type to the cuboctahedron. The stereophonic sound according to any one of claims 1 to 6, wherein the sound recording space and the sound reproduction space are the same space, and the sound recording polyhedron and the sound reproduction polyhedron are approximately congruent. system. A recording device used in the stereophonic system according to any one of claims 1 to 4.
A recording device in which all of the microphones are three-dimensionally arranged in the acoustic recording space. A recording device used in the stereophonic system according to claim 5 or 6.
A recording device in which at least one of the microphone and the dual microphone is three-dimensionally arranged in the acoustic recording space. A reproduction device used in the stereophonic system according to any one of claims 1 to 4.
A reproduction device in which all of the speakers are three-dimensionally arranged in the acoustic reproduction space. A reproduction device used in the stereophonic system according to claim 5 or 6.
A reproduction device in which at least one of the speaker and the dual speaker is three-dimensionally arranged in the acoustic reproduction space. The reproduction device according to claim 10 or 11, further comprising a speaker enclosure in which the microphone is provided so that the sound recording polyhedron and the sound reproduction polyhedron are substantially congruent.

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