JP3335409B2 - Reverberation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for predicting a sound field, and more particularly to a reverberation adding apparatus capable of performing a natural sound field simulation of two channels.

[Summary of the Invention] The present invention predicts and estimates a natural two-channel time response (impulse response from a sound source to a sound receiving point) from the limited data in terms of the audibility of a reflected sound in a room at a design stage. A new algorithm that estimates and adds the time series data of the reverberation sound based on the time series data of the initial reflection sound of two channels obtained by computer simulation and the reverberation time frequency characteristic data obtained at the time of sound design. This is to predict and simulate after the natural early reflection sound (rear reverberation sound) in terms of hearing.

[0003]

2. Description of the Related Art In a conventional sound field simulation, a rear reverberation sound following an initial reflection sound has been added by trial and error (for example, Fumie Sakamoto et al., "Acoustic simulation of Gunma Symphony Hall", IEICE technical research). Report, Vol.91, No.250 (applied sound), P4
6, see September 27, 1991).

As methods already established, a ray tracing method and a virtual image method (image metho
d) is also known.

In this case, the sound ray tracing method uses 200 to 3 wall surfaces.
The sound field such as the concert hall of the standard size of 00,
The sound source emits a large number of sound rays at equal solid angle intervals and traces and calculates the reflected propagation path to find the initial reflected sound and the rear reverberation sound. Predict and simulate

In the virtual image method, a virtual sound source is geometrically obtained by reflection from each wall, and a path from the virtual sound source to an observation point is plotted. Approximately calculated initial reflected sound and rear reverberation sound are calculated, and a natural initial reflected sound and later (rear reverberation sound) are predicted and simulated.

However, any of these methods requires a huge amount of calculation, so that it is quite difficult even at present, when the processing speed of the computer has been dramatically improved.

[0008]

By the way, as a conventional reverberation adding method, when the initial sound part is monaural, there is a well-established method which can be realized even with the current computer (for example, "Sound field" Optimal Algorithm for Adding Reverberation in Prediction ").

However, it has been quite difficult at present to add a natural reverberation sound to the initial sound portions of the two left and right channels reaching the both ears from the sound source.

[0010] In view of the above circumstances, the present invention reaches from the sound source that can be simulated at a practical level to the left and right ears of the sound receiving point.
Based on the initial reflected sound of the channel (for example, a reflected sound within a delay time of 100 ms after the arrival of the direct sound) and the reverberation time frequency characteristics of the room that can be predicted from the room shape, the sound absorption coefficient of the interior material, etc. It is an object of the present invention to provide a reverberation adding device capable of predicting and simulating a reflected sound (rear reverberation sound) after an initial reflected sound.

[0011]

In order to achieve the above object, a reverberation adding apparatus according to the present invention comprises two channels from a sound source in a room to be simulated based on a sound field simulation to both right and left ears at a sound receiving point. Means for obtaining an initial reflection impulse response for each band, and a reverberation time frequency characteristic of a room to be simulated for each channel, and a random number for each band so as to satisfy the obtained reverberation time frequency characteristic. Second for finding pulse trains a (t) and b (t) having different sequences
And a rear reverberation impulse response Rl for each of the left and right bands.
A third means for obtaining (t) and Rr (t) by the following equations: Rl (t) = a (t) + α · b (t) Rr (t) = α · a (t) + b (t) The cross-correlation coefficient of the initial reflection sound based on the initial reflection impulse responses Pl (t) and Pr (t) matches the cross-correlation coefficient of the rear reverberation sound based on the rear reverberation impulse responses Rl (t) and Rr (t). And a fourth means for determining the rear reverberation impulse responses Rl (t) and Rr (t) for each of the left and right bands, and an initial reflection impulse response Pl (t) for each of the left and right bands. ), Pr (t) and the rear reverberation impulse responses Rl (t), Pr (t), and the left and right simulated impulse responses by combining the combined impulse responses for each band. And (6) means.

[0012]

According to the present invention, first, based on a sound field simulation, an initial reflection impulse response for each band of two channels from a sound source in a room to be simulated to a left and right ear at a sound receiving point is obtained. Further, the reverberation time-frequency characteristic of the room to be simulated is obtained for each channel, and pulse trains a (t) and b (t) having different random number sequences are obtained for each band so as to satisfy the obtained reverberation time-frequency characteristic. Ask. Further, a rear reverberation impulse response Rl (t), Rr for each of the left and right bands.
(T) is obtained by the following equation. Rl (t) = a (t) + α · b (t) Rr (t) = α · a (t) + b (t) Then, the initial reflection impulse response Pl (t), Pr
The value of the constant α is determined so that the cross-correlation coefficient of the initial reflection sound based on (t) and the cross-correlation coefficient of the rear reverberation sound based on the rear reverberation impulse responses Rl (t) and Rr (t) match. Rear reverberation impulse response Rl for each band
(T), Rr (t) are determined, and an initial reflection impulse response Pl (t), Pr (t) and a rear reverberation impulse response Rl (t), Pr (t) are synthesized for each of the left and right bands, The left and right simulated impulse responses are obtained by combining the combined impulse responses of the respective bands. As described above, the present invention is a new apparatus for predicting and estimating the natural two-channel time response (impulse response from the sound source to the sound receiving point) in the design stage from the limited data in terms of the audibility of the reflected sound in the room. Estimate and add the time series data of the reverberation sound based on the time series data of the two-channel initial reflection sound obtained by sound field simulation and the reverberation time frequency characteristic data obtained at the time of acoustic design, and add natural Predict and simulate after the initial reflected sound (rear reverberation).

[0013]

FIG. 1 is a block diagram showing an example of a simulation system to which an embodiment of a reverberation adding apparatus according to the present invention is applied.

The simulation system shown in FIG. 1 includes a room-shaped data input unit 1, a dry source unit 2, a calculation unit 3, a right channel D / A conversion unit 4, and a left channel D / A conversion unit.
Only the information of the two-channel initial reflection sound response from the sound source to the left and right ears of the sound receiving point and the reverberation time frequency characteristics of the room, which are provided with the A conversion unit 5 and the headphones 6 and can be predicted at the time of room acoustic design By making the correlation coefficient between the initial sound portions of the two left and right channels and the correlation coefficient of the rear reverberation sound portion of the two left and right channels coincide with each other, the natural reflected sound ( Predict and simulate rear reverberation.

The room data input unit 1 receives room shape data such as the area of the wall surface of the room, the sound absorption coefficient of the interior material, and the room capacity, etc., and supplies them to the calculation unit 3.

The dry source unit 2 generates a uniform random number having a different random number sequence in the time axis direction for each band (each frequency band) and supplies the same to the calculation unit 3.

The calculation section 3 is used as a CPU such as a microprocessor for performing various processes, a ROM in which a program for defining the operation of the CPU and various constant data are stored, and a work area of the CPU. It includes a RAM, etc., and fetches various data output from the room-shaped data input unit 1 and signals output from the dry source unit 2 by a program stored in the ROM to obtain an initial reflection sound of the right channel. , A process 11 of generating an initial reflection of the left channel, a process 12 of generating a rear reverberation of the right channel,
Processing 13 for generating the rear reverberation of the left channel, processing 14 for adding the initial reflection of the right channel and the rear reverberation 14, processing 1 for adding the initial reflection of the left channel and the rear reverberation
5, the convolution operation processing 16 on the right channel side and the convolution operation processing 17 on the left channel side are performed, and the digital right channel sound signal simulated by each of these processes is sent to the right channel D / A conversion unit 4. A digital left channel sound signal simulated by each process is supplied to the left channel D / A converter 5.

The right-channel D / A converter 4 takes in the right-channel sound signal output from the calculator 3 by the D / A converter 20 and D / A converts the right-channel sound signal into an analog right-channel sound. After the signal is generated, the right channel sound signal is amplified by the amplifier circuit 21 and output as sound from the right channel speaker 23 of the headphones 6.

Further, the left channel D / A conversion unit 5 outputs a D / A
The A-channel conversion circuit 24 captures the left-channel sound signal output from the calculation unit 3 and D / A converts the left-channel sound signal to generate an analog left-channel sound signal. Is amplified and output from the left channel speaker 26 of the headphones 6 as sound.

Next, the operation of this embodiment will be described with reference to the flowchart shown in FIG.

First, the calculation unit 3 calculates the room shape data such as the area of the room wall surface, the sound absorption coefficient of the interior material and the room volume, etc. input from the room shape data input unit 1, the sound source position, and the positions of the left and right ears at the sound receiving point. By using a ray tracing method or a virtual image method generally used as a sound field simulation, an impulse response of two channels from the sound source to the left and right ears at the sound receiving point is obtained. At this time, the range for obtaining the reflected sound is, from a practical point of view, a time delay after the arrival of the direct sound (hereinafter referred to as DT).
This is called an initial portion (initial reflected sound) of about 100 ms (step ST1).

Thus, when the relationship between the sound source and the left and right sound receiving points is set as shown in FIG.
As shown in (b), the initial reflected sound of the left channel and the initial reflected sound of the right channel are obtained.

Thereafter, the calculation unit 3 applies a band-pass filter (BFP) 30 to the initial reflected sound portions of both the left and right channels to obtain the start level L (DT) of the rear reverberation sound at the time DT in each band ( Step ST
2).

In this case, as shown in FIG.
(DT) is 10 for each channel based on the time DT.
The maximum value of the amplitude of the initial reflected sound from before ms to time DT is obtained, and the smaller one of these maximum values is commonly used.

As a result, the initial reflected sound portion is shown in FIG.
In the state shown in FIG. 4B, the start levels L (DT) of the left and right channels are determined as shown in FIG.

On the other hand, for the rear reverberation, the calculation unit 3 firstly calculates the area of the room wall surface input from the room type data input unit 1,
As shown in FIG. 4D, the reverberation time frequency characteristic of the room to be simulated is obtained by using the Eyring's formula for obtaining the reverberation time of the room from the sound absorption coefficient of the interior material and the room capacity (step ST3).

After that, the calculation unit 3 generates uniform random numbers in the time axis direction in each band by the dry source unit 2 and calculates a pulse train obtained by these uniform random numbers and the reverberation time frequency characteristic. FIG. 4 based on
After calculating a pulse train having a predetermined reverberation envelope having a different random number sequence as shown in (e), a band-pass filter is applied and two types of pulse trains a (t) and b are provided for each band.
(T) is made (step ST4).

Next, the calculation unit 3 defines the reverberation parts of the left and right channels as shown in the following equations, and creates reverberation sounds for each band as shown in FIG.

Rl (t) = a (t) + α · b (t)
Reverberation part of the left channel Rr (t) = α · a (t) + b (t) ... Reverberation part of the right channel Thereafter, the calculation unit 3 calculates the cross-correlation coefficient of the initial sound part and the reverberation as shown in the following equation. While calculating the cross-correlation coefficient of the sound part, the cross-correlation coefficient of the left and right channels of the initial sound part and the cross-correlation coefficient of the left and right channels of the reverberation part are calculated as shown in FIGS. The value of the constant α is repeatedly adjusted so as to match (step ST5).

[0030]

(Equation 1) Then, if a constant α that matches the cross-correlation coefficient of the initial sound part and the cross-correlation coefficient of the reverberation sound part is obtained,
Is an initial sound part shown in FIG. 4C as shown in FIG.
After adding the reverberation part obtained by the above-described operation for each band, the sound of each band is synthesized for each channel as shown in FIG. Are supplied to the right channel D / A converter 4 and the left channel D / A converter 5, respectively, and the right channel speaker 2 of the headphones 6 is supplied.
3. Output from the left channel speaker 26.

As described above, in this embodiment, only information on the two-channel initial reflected sound response from the sound source to the left and right ears of the sound receiving point and the reverberation time frequency characteristics of the room, which can be predicted when designing the room acoustics, are used. Since the correlation between the initial sound signals of the two left and right channels and the correlation of the left and right signals of the rear reverberation sound are made to match each other, the reflection sound after the natural initial reflection sound (the rear part) at a practical level is audibly natural. Reverberation) can be predicted and simulated.

As a result, by using this reverberation addition method, it is possible to predict and simulate the rear reverberation sound at the design stage, so that it is possible to easily simulate the two-channel impulse response which has been difficult in the past. , Can be used as future multi-channel sound field simulation.

Furthermore, a natural two-channel sound can be imitated in terms of audibility only by the information of the initial reflected sound response of two channels from the sound source to the left and right ears of the sound receiving point and the information of the reverberation time frequency characteristics of the room. Even if the actual two-channel sound is compressed with high efficiency using only the information of the two-channel initial reflected sound response from the sound source to the left and right ears of the sound receiving point and the reverberation time frequency characteristics of the room, the compressed sound The sound in the actual sound field can be simulated based on the data and the information of the initial reflected sound response of two channels from the sound source to the left and right ears of the sound receiving point and information on the reverberation time frequency characteristics of the room.

[0034]

As described above, according to the present invention, two channels of early reflections reaching the left and right ears of a sound receiving point from a sound source that can be simulated at a practical level (for example, delayed after the arrival of direct sound) Based on the reverberation time frequency characteristics of the room, which can be predicted from the room shape, the sound absorption rate of the interior material, etc., the reflected sound after the natural initial reflected sound (rear reverberation sound) is predicted based on the room shape, the sound absorption coefficient of the interior material, etc. Can be simulated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a simulation system to which an embodiment of a reverberation adding apparatus according to the present invention is applied.

FIG. 2 is a flowchart showing an operation example of the simulation system shown in FIG.

FIG. 3 shows a start level L of a rear reverberation sound of the calculation unit shown in FIG. 1;
It is a schematic diagram which shows the (DT) determination operation example.

FIG. 4 is a schematic diagram showing an example of a simulation operation of the calculation unit shown in FIG. 1;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Room-shaped data input part 2 Dry source part 3 Calculation part 4 Right channel D / A conversion part 5 Left channel D / A conversion part 6 Headphones 10 Processing which generates the initial reflection sound of the right channel 11 The initial reflection sound of the left channel Processing for Generating 12 Processing for Generating Right Reverberation 13 Processing for Generating Left Reverberation 14 Processing for Adding Right-Channel Initial Reflection and Rear Reverberation 15 Left-Channel Initial Reflection and Rear Processing for adding reverberation sound 16 Convolution operation processing for right channel 17 Convolution operation for left channel 20 D / A conversion circuit 21 Amplification circuit 23 Speaker on right channel 24 D / A conversion circuit 25 Amplification circuit 26 Left channel side Speaker

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G10K 15/12 G10K 15/00 H04S 1/00 G01H 7/00

Claims (1)

(57) [Claims] A first means for obtaining an initial reflection impulse response for each band of two channels from a sound source in a room to be simulated to a left and right ear at a sound receiving point based on a sound field simulation; and The reverberation time frequency characteristics of the room are obtained for each channel, and pulse trains a (t) and b having different random number sequences for each band so as to satisfy the obtained reverberation time frequency characteristics.
Second means for determining (t); and a rear reverberation impulse response Rl (t), R for each of the left and right bands.
R3 (t) = a (t) + α · b (t) Rr (t) = α · a (t) + b (t) Initial reflection impulse response A constant such that the cross-correlation coefficient of the initial reflection sound based on Pl (t) and Pr (t) and the cross-correlation coefficient of the rear reverberation sound based on the rear reverberation impulse response Rl (t) and Rr (t) match. Fourth means for obtaining the value of α and determining the rear reverberation impulse responses Rl (t), Rr (t) for each of the left and right bands, and for each of the left and right bands, the initial reflection impulse response Pl (t),
Pr (t) and rear reverberation impulse response Rl (t), Pr
(T) and sixth means for synthesizing the combined impulse responses of the respective bands to obtain simulated left and right impulse responses.