JPH05115098A - Stereophonic sound field synthesis method - Google Patents

Abstract

PURPOSE:To improve the accuracy of acoustic simulation by obtaining an impulse response to a solid angle in the incoming direction of sound as to a sound receiving point in a sound field with respect to the stereophonic sound field synthesis method in which a sound image is reproduced by two systems employing left and right channels. CONSTITUTION:It is required to cancel (CL, CR) crosstalk of left and right channels to reproduce impulse response shared to the left and the right channels by two systems employing the left and right channels. That is, the sound entering a left ear from a right speaker 1 is canceled by the sound from a left speaker 2 and the converse action is also true. Moreover, front correction (EL, ER) and correction (TL, TR) of the reproduction system including speakers are implemented as to each channel. Since the impulse response subjected to correction with an acoustic characteristic corresponding to the left right ears is shared to the left and right channels and then synthesized, an accurate stereophonic sound field is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to reproducing a sound image in two systems of a left channel and a right channel, and particularly, the impulse response for each direction at the listener's position and the acoustic characteristics of the listener make the listener's sound characteristic. The present invention relates to a stereophonic sound synthesis method for determining a response to be input to both ears.

[0002]

2. Description of the Related Art As is well known, in music halls and the like, it is important to analyze the sound field at the design stage. Therefore, as a technique for analyzing the sound field, the virtual image method, which is a geometrical method, is known. .. The virtual image method is based on Fermat's theorem that a phenomenon in the natural world travels through the shortest distance, and obtains a sound response by geometrically tracing the sound reaching the sound receiving point. As a technology to reproduce the sound field from the calculated response, multiple speakers are appropriately placed in a space such as an anechoic room where unnecessary reflections do not occur, and a listening test is performed in the center of the room.
Is being done.

[0003]

However, the geometrical simulation represented by the virtual image method has a problem that the diffraction of the sound cannot be expressed because the sound is treated geometrically. That is, in the geometric simulation,
Sound simulation can be properly performed only under the limited condition that sound diffraction can be ignored, but it is special and sound diffraction is often not negligible, so the simulation accuracy is not good and high accuracy. Was difficult to do. In addition, not only direct sound from the sound source but also reflected sound comes from a certain direction at the actual sound receiving point, but the speaker to simulate this is infinite in an anechoic room. However, the simulation accuracy is limited due to the limitation of the number of speakers. Moreover, placing a large number of speakers in an anechoic room is not desirable in terms of facility cost because the installation location of the device is limited.

As a technique for reproducing a three-dimensional sound field with two systems of a left channel and a right channel, a HATS (Head And Torso Simul) as shown in FIG. 2 is used.
What is called a maker), that is, a doll that imitates the human head and torso with microphones placed on the left and right ears respectively, is recorded, and when this is played, the left and right channel crosses are recorded. It is known to cancel the talk, correct speaker characteristics, and perform frontal correction to fit characteristics such as the shape of HATS to those of the listener, which is a recording / playback technique in an existing sound field. It is not established as the simulation technique mentioned in.

The present invention has been made in view of the above circumstances, and an object thereof is to obtain a three-dimensional sound field by two systems of a left channel and a right channel, and to perform acoustic simulation with high accuracy and reproduction. An object of the present invention is to provide a method for stereophonic sound generation, which has a high degree of freedom in formality and is advantageous in terms of equipment cost.

[0006]

In order to achieve the above object, the present invention provides a stereophonic sound synthesizing method for reproducing a sound image in two systems of a left channel and a right channel, and a sound arrival direction at a sound receiving point in a sound field. It is characterized in that the impulse response corresponding to the solid angle of is obtained and the acoustic characteristics of the left and right ears are given to each impulse response, so that those impulse responses are distributed to the left channel and the right channel.

[0007]

The operation of the present invention will be described. First, the impulse response corresponding to the solid angle in the direction of arrival of sound as the acoustic characteristic of the air conditioning, that is, the sound field with respect to the sound receiving point is obtained.
Then, the acoustic characteristics of the left and right ears are given to each impulse response, so that the correction corresponding to the left and right ears of the listener is performed.After that, those impulse responses are compared to the left channel and the right channel. The sound image can be reproduced in two systems, the left channel and the right channel, and a stereoscopic sound field can be obtained.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows an embodiment of the present invention. In the present invention, basically, in a stereophonic sound synthesizing method for reproducing a sound image with two systems of a left channel and a right channel, a sound receiving point in a sound field is The impulse response corresponding to the solid angle in the direction of sound arrival is determined, and the acoustic characteristics of the left and right ears are given to each impulse response to distribute those impulse responses to the left channel and the right channel. Acoustic simulation is performed with two systems, the right channel and the right channel.

The impulse response is based on the Kirchhoff integral equation, which is an integral expression of the wave equation,
The elements to be discretized are assumed to be in-phase elements of the wavefront, and the number of elements can be relatively suppressed to calculate in real time. The solid angle of the sound receiving point in the sound field extends in all directions centering on the sound receiving point, and therefore indicates the arrival direction of the sound with respect to the sound receiving point. Specifically, for the sound receiving point, the impulse response is obtained by appropriately dividing the solid angle into variables. Therefore, the impulse response is obtained for each direction, which can be said to be the acoustic characteristic of the space related to the sound receiving point, that is, the sound field.

By the way, humans perceive sound coming from a certain direction with the left and right ears, and determine the direction of arrival with the acoustic characteristics of the left and right ears, that is, the difference in sound level between the left and right ears, the time difference, the difference in frequency characteristics, and the position. Since it is empirically specified by the phase difference etc.,
To each impulse response that can be said to be directionally, the acoustic characteristics of the left and right ears are corrected according to the direction, and the responses of the left and right ears of the listener are synthesized. The impulse response distributed to the left and right is reproduced by two systems, the left channel and the right channel. In the reproduction of these two systems, as shown in FIG. 1, it is necessary to cancel crosstalk (C _L C _R ) of the left and right channels,
That is, the sound coming from the right speaker 1 to the left ear is canceled by the sound output from the left speaker 2, and vice versa. Further, front correction (E _L , E _R ) correction of reproduction system including speakers ( _TL , T) for each channel
_R ) also do. The right speaker 1 and the left speaker 2
Is suitable such as a fixed type grounded on the floor surface or the like, or a headphone type set on the head by the listener.

As described above, since the impulse response with the corrected acoustic characteristics corresponding to the left and right ears of the listener is distributed to the left channel and the right channel and synthesized, the two channels of the left channel and the right channel are auditioned. A sound image can be reproduced by accurately inputting signals to both ears of a person. This impulse response is obtained for each direction, so to speak, with respect to the solid angle. Therefore, although the reproduction is performed by two systems, the reproduced localization is exactly three-dimensional, and a three-dimensional sound field can be obtained. Therefore, the acoustic simulation can be performed with high accuracy by increasing the variance number of the solid angle, that is, the number of calculations of the impulse response.
Theoretically there is no limit to the simulation accuracy. Also,
Since it uses two systems, a left channel and a right channel, it is advantageous in terms of equipment cost.

[0012]

As described in detail above, according to the stereophonic sound synthesizing method of the present invention, the impulse response can be obtained for each direction at the sound receiving point in the sound field, which is the left and right ears of the listener. Is corrected and then the impulse responses thereof are distributed to the left channel and the right channel and synthesized, so that the sound image can be reproduced by the two systems of the left channel and the right channel. And since the impulse response is obtained for each direction with respect to the solid angle, although the reproduction is two systems, the reproduced localization is exactly three-dimensional.
A three-dimensional sound field can be obtained. Therefore, the acoustic simulation can be performed with high accuracy in accordance with the increase in the number of divisions of the solid angle of the impulse response, and since it is simply based on two systems, there is a large degree of freedom in the reproduction function, and there is an advantage in terms of equipment cost. is there.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a reproducing system according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional HATS technique related to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsutoshi Watanabe 4-640 Shimoseido, Kiyose-shi, Tokyo Obayashi Corporation Technical Research Institute

Claims (1)

[Claims] 1. In a stereophonic sound synthesizing method for reproducing a sound image in two systems of a left channel and a right channel, an impulse response corresponding to a solid angle in a sound arrival direction is obtained for a sound receiving point in a sound field, and left and right ears are obtained. A stereophonic sound synthesizing method, characterized in that the impulse response is given to each impulse response, and the impulse responses are distributed to the left channel and the right channel and synthesized.