JPH06250678A - Sound field reproducing method - Google Patents

Abstract

PURPOSE:To provide a sound phenomenon equivalent to sound source field to an audience with a few speakers without inserting small-sized microphones into ears. CONSTITUTION:The microphones 41-48 are arranged on respective vertexes of a tetrahedron in the periphery of both ears of a dummy head 3 in the sound source field 1, and the outputs of respective microphones 41-48 are supplied to one input nine outputs FIR filters 51-58. The microphones 91-98 are arranged on the periphery of both ears of the audience 8 in a reproduction sound field 6 in the same relation as the relative positions of the microphones 41-48 and the dummy head 3, and respective nine outputs of the filters 51-58 are supplied to the speakers 71-78 in the reproduction sound field 6 respectively, and filter coefficients are set so that the outputs of the microphones 91-98 coincide with the outputs of the corresponding microphones 41-48.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound field reproducing method for accurately reproducing a sound event such as voice and music which a listener feels in the original sound field with a speaker in a place apart from the original sound field.

[0002]

2. Description of the Related Art Such sound field reproduction methods are roughly classified into (1) transaural reproduction method and (2) multiple sound source reproduction method. The trans-aural reproduction method is a reproduction method in which the ear input signal of the listener is matched with the ear input signal in the original sound field to make the listener feel the same acoustic event as in the original sound field. The feature of this method is that the above effect can be achieved even with a small number of speakers, such as a few speakers. However, in principle, the sound pressure on the eardrum surface of the listener or the listener's external auditory meatus entrance sound pressure equivalent to this is required, so that there are the following restrictions.

(A) In order to continuously present the original sound field acoustic events to the listener, the ear input signal must be controlled according to the change in the sound pressure on the eardrum surface due to the rotation of the listener's head. However, for this purpose, wear small microphones on both ears of the listener.
It is necessary to insert it and observe the above sound pressure change. (B) When the small microphone is not used, it is necessary to force the listener to hold an unreasonable posture such as fixing the head during reproduction.

The multi-source reproduction method (2) is further divided into two. One is (2-1) by installing a large number of speakers around the listener and radiating sound signals with different amplitudes and arrival times to the listener from these speakers,
This is a method of reproducing the reflected sound structure of the original sound field, and the other is (2-2) adjusting the amplitude / phase difference (time difference) of the sound signals radiated from a large number of loudspeakers to produce sound around the listener. This is a method of presenting to the listener an acoustic event as if sound waves were emitted from the virtual image by generating a virtual image.

In these multi-source reproduction methods, the above restrictions (a) and (b) found in the transaural reproduction method are eliminated. However, (c) hundreds of speakers are required to present a highly accurate original sound field event to the listener. (D) It is necessary to limit the reproduction space to a room such as an anechoic room that has been subjected to a high degree of sound absorption processing. There was an unavoidable problem in principle.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to reproduce sound signals using a relatively small number (several dozen or less) of speakers so that the listener's ears can be heard even in a room where no sound absorbing treatment is applied. Without installing or inserting a small microphone,
An object of the present invention is to provide a sound field reproducing method for presenting a listener with the same acoustic event as the original sound field.

[0007]

According to the present invention, at least three first microphones are arranged on both sides around the listener's head in a reproduced sound field, and the relative positions are the same as the relative positions of these first microphones. , The same number of second microphones are arranged in the original sound field, and the respective outputs of the second microphones are supplied to the same number of 1-input n-output (n is an integer equal to or larger than the number of the first microphones) filters, respectively. The n outputs of the first microphone are synthetically supplied to the n speakers arranged in the reproduction sound field, and the respective outputs of the first microphone are equalized with the outputs of the second microphone at the position corresponding to the first microphone. Set the filter coefficient of.

[0008]

FIG. 1 shows an embodiment of the present invention. The sound signal radiated from the sound source 2 in the original sound field 1 is a microphone 4 ₁ , 4 arranged at each vertex of a tetrahedron surrounding each ear of the dummy head 3 having acoustic characteristics very similar to the listener's head. ₂ ,
… Sounds are received by 4 ₈ . Each microphone 4 ₁ , 4
_2, ..., 4 filter 5 ₁ output signals of the respective one inputs 9 output _8, 5 _2, ..., is supplied to the 5 _8. Each filter 5
_i (i = 1, 2, ..., 8) has a common input 9
Each of the nine outputs of each filter 5 _i is supplied to the speakers 7 ₁ , 7 ₂ , ..., 7 ₈ arranged in the reproduced sound field 6, and these speakers are arranged in the reproduced sound field 6. Is emitted to. The dummy head 3 and the microphones 4 ₁ , 4 ₂ , ..., 4 ₈ are arranged in the reproduction sound field 6 so as to have the same positional relationship with each other, and the microphones 9 ₁ , 9 ₂ ,. Speakers 7 ₁ , 7 at ₈
The acoustic signals from ₂ , ..., 7 ₉ are received. The filter setting device 10 allows the microphones 9 _{1 at} positions corresponding to the output signals of the microphones 4 ₁ , 4 ₂ , ..., 4 ₈ , respectively.
The filter coefficients of each of the filters 5 ₁ , 5 ₂ , ..., 5 ₈ are calculated so that the output signals of 9 ₂ , ..., 9 ₈ are equal, and these coefficients are assigned to the filters 5 ₁ , 5 ₂ ,. Set to ₈ . This filter coefficient is calculated, for example, in Japanese Patent Application No.
It may be performed by using the sequential operation method described in No. 53886.

In this way, the sound wave surface formed according to the sound pressure distribution and the sound pressure gradient around the ears of the listener 8 in the reproduced sound field 6 is the same as that of the dummy head 3 existing in the original sound field 1. It closely approximates the sound wave surface formed around both ears. As a result, the listener 8 in the reproduced sound field 6 can be presented with an acoustic event as if he were in the original sound field 1. Now, it is assumed that each microphone 9 _i (at each position of i = 1, 2, ... 4) is generating an acoustic signal x _i having a wave number and a center frequency of k _c . The signal observed at the point P _A in the area surrounded by these microphones 9 _i is expressed as follows.

X _A = Σ _i a _i x _i + r _A (1) r _A is noise and the time average of x _i r _A is zero, and a _i is a linear value that minimizes the time average of | r _A | ^2. It is a prediction coefficient. Assuming the diffuseness of the sound field around the microphone 9 _i , the acoustic power of the signal x _A is calculated as follows.

| X_A｜² _m= Σ_iΣ_ja_ia_jx_ix_j
+ | R_A｜² _m | R_A｜² _m= (1-Σ_ia_iρ_i) Σ_i| X_i｜² _m
/ N | x_i｜² _mThe subscript m is | x_i｜²Shows the time average of
And ρ_iIs a microphone 9 _iAnd point P_AThe distance between
_iWhen, ρ_i= Sin (k_cd_i) / (K_cd_i), The correlation coefficient between two points, N is the number of microphones,
In this example N = 4. Microphone 9_iSurrounded by
2 points P in the shaded area_A, P_BSound power ratio | x_A
｜² _m/ | X_B｜² _m(Sound pressure gradient) is a microphone
9_i, 9_jSignal x generated at_i, X_jLevel of
Can be controlled by adjusting the difference and phase difference (time difference)
It Also | x_A｜² _mFrom the formula 9_iSurrounded by
Microphone 9_iGenerated at
Signal x_iCan be controlled by adjusting. this
So Σ_i| X_i｜² _mSignal under the condition that is constant
x_i, X_jBy adjusting P_A, P_BIn
The sound power ratio (sound) between two points without changing the noise level.
The pressure gradient) and the sound pressure distribution can be controlled.

That is, the microphone 9_iOf the area surrounded by
The speaker 7 displays the sound pressure distribution and the sound pressure gradient at any place.₁~ 7
₉Can be controlled by controlling the acoustic signal of
Microphone 9_Five~ 9₈Any in the area surrounded by
The sound pressure distribution and the sound pressure gradient at the points of₁~ 7₉
Can be controlled by controlling the acoustic signal of
Wear. From this, both ears of the listener 8 in the reproduction sound field
Microphone 9₁~ 9 _FourAnd 9_Five~ 9₈And surround
The sound field in both ears will be
It is understood that the sound field of the corresponding part can be controlled in the same way.
It

The reproduced sound field 6 is sufficiently sound-absorbed.
If the filter and the speakers in the playback sound field 6 are
Even if the same number of microphones are placed around both ears of listener 8
The same effect as described above can be obtained. In addition, live around the listener 8.
A sound wave surface to be formed is formed around the dummy head 3.
In order to get closer to the sound wave surface, the dummy head 3 and listening
The number of microphones around person 8 should be increased. Also above
Here, filter 5₁~ 5₈Is a DSP (digital signal
Processor) chip, in which case
Microphone 4 chips₁~ 4₈Is not necessarily the number of
I don't. Also, depending on the case, one digital file
The output of one microphone of the
In some cases, the number of outputs may be extracted, so the point is that
Black phone 4₁~ 4₈Input one of each output of
9 speakers for each input ₁~ 7₉9 outings to
If it is possible to output power by controlling each force
Good. Also, it is only necessary to be able to reproduce the stereo sound field in the left and right directions.
If it is around each ear in a horizontal plane, including the listener's ears
A minimum of three microphones may be provided for each. in this case
At the entrance of each ear or inside the three microphones
It is better to be located in the enclosed horizontal plane.

[0014]

As described above, by using the sound field reproducing method of the present invention, it is possible to insert the microphone into the ear without inserting the microphone.
By reproducing the sound signal using a relatively small number of speakers, a sound wave surface that closely approximates the sound wave surface of the original sound field is generated around the listener's head (or both ears) in the reproduction space with arbitrary reverberation characteristics. As a result, the listener can be presented with an acoustic event as if he were in the original sound field.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // E04B 1/99 Z 7521-2E

Claims (1)

[Claims] 1. At least three first microphones are arranged on both sides around a listener's head in a reproduced sound field, and the same number of second microphones are arranged at the same relative position as the relative position of these first microphones. And each output of these second microphones is supplied to the same number of 1-input n-output (n is an integer equal to or greater than the number of the first microphone) filters, and n outputs of each of these filters are reproduced in the reproduction sound field. Are combined and supplied to the n speakers arranged in, and the filter coefficient of each filter is set so that each output of the first microphone becomes equal to the output of the second microphone at a position corresponding to the same. Sound field reproduction method to reproduce the original sound field.