JPH09292885A - Acoustic space impulse response estimating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an acoustic space impulse response estimating device with a small number of times of product-sum operation. SOLUTION: A digital filter 16 sets the transport time and level of direct and reflection waves against an impulse input from an input terminal 10. A digital filter 13 has as characteristics components eliminating the transport time from the impulse response of only direct waves, performs product-sum operation between the output of the digital filter 16 and its component, and obtains the direct and wave and plural reflection waves.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic space impulse for estimating an acoustic space impulse response used for a voice man-machine interface of a voice conference or a video conference (hereinafter referred to as a TV conference), a voice processing of virtual reality, and the like. The present invention relates to a response estimation device.

[0002]

2. Description of the Related Art In stereophonic reproduction of sound in a voice conference or a TV conference, the reflected sound and the reverberant sound are electrically operated in order to give a realistic sensation of listening to music in a concert hall. ing. In order to realize this operation, it is necessary to find the acoustic spatial impulse response in the hall or room. That is, it is necessary to find what waveform the impulse emitted from the speaker of the sound source reaches the microphone. Conventionally, DSP (Digital Si
The impulse response was estimated by an acoustic space impulse response estimation device using a gnal Processor (digital signal processor) or the like.

[0003]

However, the conventional acoustic space impulse response estimation device has the following problems. The length of the impulse response in a normal room reaches 0.2 to 0.6 seconds due to the influence of higher-order reflected waves. There is a problem in that the amount of calculation increases when processing such high-order reflections. Hereinafter, the reason will be described. FIG. 2 is a diagram for geometrically explaining the reflected wave and the direct wave of the sound, and shows the direct wave and the reflected wave in the room. Room 1
The sound waves emitted from the speaker 2 arranged inside reach the microphone 3 through various paths kd, k1, k2, k3, k4, k5 and k6. The route kd is a route of a direct wave directly input from the speaker 2 to the microphone 3. Each route k
The sound waves propagating through 1 and k2 are reflected twice by the wall of the room 1 and reach the microphones 3, respectively. The sound waves propagating through the paths k3 and k4 are reflected once and reach the microphone 3. The sound waves propagating through the paths k5 and k6 also reach the microphone 3 after being reflected twice by the wall. That is, the sound wave that propagates through each of the paths k1 to k6 and reaches the microphone 3 is a reflected wave. Route k3, k4
The sound wave that propagates through and reaches the microphone 3 is a primary reflected wave, and the sound wave that propagates through the paths k1, k2, k5, k6 and reaches the microphone 3 is a secondary reflected wave. Z1, z2 in FIG.
z3, z4, z5, and z6 are virtual images of the speaker 2 when sound waves are viewed from the microphone 3 side. That is, in the microphone 3, the speaker 2 is arranged at the positions of the virtual images z1 to z6.
Sound waves are being input.

FIG. 3 is a diagram showing a sound wave and an impulse waveform input to the microphone 3 in FIG. In FIG. 3, the direct wave Sd propagating on the route kd, the primary reflected waves S3 and S4 propagating on the routes k3 and k4, the secondary reflected waves S1 and S2 propagating on the routes k1 and k2, and the routes k5 and k6. The secondary reflected waves S5 and S6 propagated through are shown. Note that, for simplification, the route k1 and the route k2, the route k3 and the route k4, and the route k5 and the route k6 are symmetrical, and the sound wave propagation distances are equal. The direct wave Sd reaches the microphone 3 after the time t0. Each of the primary reflected waves S3 and S4 has time t
The microphones 3 arrive after 1 each. Each secondary reflected wave S
1, S2 reach the microphone 3 after time t2,
The secondary reflected waves S5 and S6 reach the microphone 3 after time t3. The reflected waves S1 and S2, the reflected waves S3 and S4, and the reflected waves S5 and S6 have different distances on the path from the speaker 2 to the microphone 3, and therefore have different arrival times at the microphone 3. Further, these reflected waves S1 to S6 are
Each time it is reflected by the wall, part of the sound energy is absorbed and attenuated. The direct wave Sd and the reflected waves S1 to S6 are combined to obtain an impulse waveform. This is the impulse response. Although only the secondary reflection is shown in FIGS. 2 and 3, since the higher-order reflection is actually present, the duration of the impulse waveform becomes longer,
It takes 0.2 to 0.6 seconds in a normal room.

FIG. 4 is a block diagram showing the configuration of a conventional acoustic spatial impulse response estimation device. The input terminal 10 is
It is a terminal to input the impulse output from the speaker,
The input terminal 10 has a plurality of delay elements 11-1, 11
-2, ..., 11-n are connected. Each delay element 11
-1 to 11-n each have a function of setting a delay time corresponding to the propagation distance of the direct wave and the reflected wave, and the number n of these delay elements 11-1 to 11-n is the direct wave and the reflected wave. (Including higher-order reflected waves). The set delay time corresponds to the times t0, t1, t2, t3, ... Of FIG. The output side of each delay element 11-1, 11-2, ... 11-n sets a multiplier 1 for setting the level of the direct wave and each reflected wave.
2-1, 12-2, ..., 12-n are respectively connected. The output sides of the multipliers 12-1, 12-2, ..., 12-n are digital filters 13-1, 13-2,
..., 13-n, respectively. The output sides of the digital filters 13-1, 13-2, ..., 13-n are connected to the accumulator 14, and the output side of the accumulator 14 is connected to the output terminal 15. The output signal from the output terminal 15 is input to the microphone. The characteristics of the digital filters 13-1 to 13-n are the same, and the delay time is excluded from the characteristics of the direct wave reaching the microphone 3. Each of the digital filters 13-1 to 13-n has a function of performing a product-sum operation on the input signal with its characteristic.

Each reflected wave can be represented as a delayed and attenuated waveform similar to the direct wave. The delay time of the reflected wave is the reflection path divided by the speed of sound and can be estimated from the geometrical arrangement of the room. Each delay element 11-1 to 11-1
11-n delays the impulse input from the input terminal 10 by the estimated delay time. Each of the multipliers 12-1 to 12-n includes each delay element 1
Coefficients α _{0 to} α _n for the output signals of 1-1 to 11- _n
To set the levels of the direct wave and each reflected wave. Each of the digital filters 13-1 to 13-n obtains the product sum of the above characteristics and the output signals of the multipliers 12-1 to 12-n and forms the waveforms of the direct wave and the reflected waves. By the accumulation of the accumulator 14, the impulse waveform of the combined impulse response is obtained. The signal duration excluding the delay time of the direct wave is about 10 to 20 ms. For example, sound 16
When sampling at kHz, a product-sum operation of about 160 to 320 samples is required. Although this is not so much calculation amount itself, when the reflected wave is also included, the calculation amount of n times is required. For example, in the case of FIG. 2, about 640 to 128.
A product-sum operation of 0 samples is required.

[0007]

According to a first aspect of the present invention, in order to solve the above-mentioned problems, there are a direct wave path and a plurality of reflected wave paths in a sound wave path from a sound source to a sound receiving point. In the acoustic space impulse response estimation device that obtains the impulse response in the acoustic space, the following configuration is used. That is, the acoustic spatial impulse response estimation apparatus of the first invention determines the propagation times of the direct wave and the plurality of reflected waves that reach the sound receiving point from the sound source and their levels with respect to the input impulse. It has a first digital filter that is estimated and set, and a component obtained by removing the propagation time from the impulse response of only the direct wave as a characteristic, and a product-sum operation of the output signal of the first digital filter and the characteristic is performed. And a second digital filter that obtains impulse responses of the direct wave and the plurality of reflected waves by performing. According to a second invention, the first digital filter in the first invention estimates and sets the propagation times and the levels of the direct wave and the plurality of reflected waves that are effective as subjective sound reception, The number of product-sum operations in the second digital filter is limited. According to the first and second aspects of the invention, since the acoustic spatial impulse response estimating apparatus is configured as described above, the propagation time of the direct wave and the plurality of reflected waves and their levels are determined by the first digital filter. It is set as a single-system signal. The first
The product-sum operation of the second digital filter is performed only on the output signal of the second digital filter. Therefore, the above problem can be solved.

[0008]

1 is a block diagram showing the configuration of an acoustic spatial impulse response estimation apparatus according to an embodiment of the present invention. In this impulse response estimation device, an input terminal 10 for inputting an impulse output from a sound source such as a speaker,
The first digital filter 16 is connected. A second digital filter 13 having a function equivalent to that of the conventional digital filters 13-1 to 13-n is connected to the output side of the digital filter 16, and the output side of the digital filter 13 is connected to the output terminal 15. There is. Two
Each of the digital filters 13 and 16 is composed of, for example, a DSP, and the signal output from the output terminal 15 is input to the microphone corresponding to the sound receiving point. Before explaining the operation of the impulse response estimation device, the function of the digital filter 16 will be described with reference to FIG.

FIG. 5 is a diagram showing a modification of the configuration of the estimation apparatus of FIG. 4, and the same elements as those in FIGS. 4 and 1 are designated by the same reference numerals. If the elements of FIG. 4 are modified in order to obtain a function equivalent to that of the conventional impulse response estimation device, the configuration of FIG. 5 can be considered. According to this, a plurality of multipliers 12-1, 12-2, ..., 12-n are connected to the input terminal 10, and the output side of each of the multipliers 12-1, 12-2 ,. , Delay elements 11-1, 11-2, ..., 11-n
Are connected respectively. Delay elements 11-1, 11
The output side of −2, ..., 11-n is connected to the accumulator 14, and the digital filter 13 is connected to the accumulator 14. Multipliers 12-1 to 12-n and delay element 11-1
.About.11-n and the accumulator 14 can be constituted by one digital filter, which is the digital filter 16 in FIG. The digital filter 16 has a function of multiplying the input impulse by a plurality of coefficients, delaying each multiplication result, and accumulating them. However, these processes are limited to effective direct wave and reflected wave components that affect subjective sound reception. By setting the number n in this way, the amount of calculation in the digital filter 13 is limited.
On the other hand, the digital filter 13 has, as the characteristics of the conventional digital filters 13-1 to 13-n, a component obtained by removing the delay time from the impulse response of the direct wave in FIG. 3 as a characteristic.

FIG. 6 shows the digital filter 16 shown in FIG.
FIG. 7 is a diagram showing the output signal of FIG. 1, and the operation of the acoustic spatial impulse response estimation device of FIG. 1 will be described with reference to FIG. 6. The digital filter 16 sets the propagation time of the direct wave and each reflected wave and their levels with respect to the impulse input from the input terminal 10. That is, by its function, the digital filter 16 multiplies the coefficients α _{0 to} α _n in consideration of attenuation due to propagation, and multiplies the result by the direct wave and each reflection estimated from the geometrical arrangement of the room as the target acoustic space. The wave delay time t0, t1, ...
One-system output signal such as The digital filter 13 multiplies and sums the output signal of the digital filter 16 and the characteristic component possessed by the digital filter 13. As a result, the impulse response of the direct wave and the reflected wave is obtained, and the impulse response is output via the output terminal 15.

Here, the number of product-sum operations will be described. Conventionally, the product-sum operation of the number of times (n × Nt) obtained by multiplying the number n of direct waves and reflected waves to be taken into consideration by the number of samples of each digital filter 13-1 to 13-n, that is, the number of taps (Nt) is performed. Was needed. On the other hand, the number of product-sum operations of the device of FIG.
Sum of tap numbers (Nt) of the digital filter 13 (n +
Nt). As described above, in the present embodiment, the digital filter 16 and the digital filter 13 that performs the sum of products operation on the output signals of the digital filter 16 constitute an acoustic spatial impulse response estimation device and expand the function of FIG. Since this is done, the number of product-sum operations can be greatly reduced compared to the conventional case. In addition, the present invention
The digital filters 13 and 16 are connected to the DSP as described above.
It can be configured by various processors such as, but can also be realized by software processing in a computer.

[0012]

As described in detail above, according to the first and second aspects of the present invention, the propagation times of the direct wave and the plurality of reflected waves and their levels are set for the input impulse. , And the second digital filter for performing the product sum calculation with the output signal of the first digital filter, the number of product sum calculations in the acoustic space impulse response estimation device is significantly larger than that of the conventional one. Can be reduced to

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an acoustic spatial impulse response estimation device showing an embodiment of the present invention.

FIG. 2 is a diagram for geometrically explaining a reflected wave and a direct wave of sound.

FIG. 3 is a diagram showing a sound wave and an impulse waveform input to a microphone 3 in FIG.

FIG. 4 is a configuration block diagram showing a conventional acoustic space impulse response estimation device.

5 is a diagram showing a modification of the configuration of the estimation device in FIG.

FIG. 6 is a diagram showing an output signal of a digital filter 16 in FIG.

[Explanation of symbols]

 1 room 2 speaker 3 microphone 13 1st digital filter 16 2nd digital filter Sd direct wave S1-S6 reflected wave t0-tn delay time

Claims (2)

[Claims] 1. An acoustic space impulse response estimation device for obtaining an impulse response in an acoustic space in which a direct wave path and a plurality of reflected wave paths exist in a sound wave path from a sound source to a sound receiving point. A first digital filter that estimates and sets the propagation times of the direct wave and the plurality of reflected waves that reach the sound receiving point from the sound source and their levels with respect to the impulse; The impulse response of the direct wave and the plurality of reflected waves is obtained by performing a product-sum operation of the output signal of the first digital filter and the characteristic, which has a characteristic that is a component excluding the propagation time from the impulse response. An acoustic space impulse response estimation apparatus comprising: a second digital filter to be obtained. 2. The first digital filter estimates and sets the propagation times and levels of the direct wave and the plurality of reflected waves, which are effective as subjective sound reception, and sets the second digital filter. The acoustic spatial impulse response estimating apparatus according to claim 1, wherein the number of multiplication and addition operations in the digital filter is limited.