JPH06265401A - Equalizing device for sound transmission characteristic - Google Patents

Abstract

PURPOSE:To prevent howling and to make the receiving of sound faithful to original sound possible by regulating an equalizer once in a system which has a sound transmission characteristic measuring section, a pole presuming section and an equalizing section, and can move a sound receiver and a sound source. CONSTITUTION:A sound source 13 and sound receivers 14 are arranged in an indoor space 11 at a plurality of different positions. In that state, a sound transmission measuring section 21 measures each sound transmission characteristic Hj (Z). For instance, the measuring section 21 measures impulse response to obtain each sound transmission characteristic Hi (Z). A pole presuming section 22 presumes a common pole A(Z) from each sound transmission characteristic Hj (Z) measured by the measuring section 21. The presuming section 22 supplys a common AR coefficient a1 corresponding to a presumed common pole A(Z) to an equalizing section 23. In the case where art signal, input into an input end 12 is x (K), the equalizing section 23 executes computation on an expression and outputs y (K) to a sound source 13. In this case, the frequency amplitude characteristic of the sound received by the sound receiver 14 becomes about equal to that of a signal input into the input end 12. Namely, when the equalizing section 23 is set up once, even if the sound receiver 14 moves, the occurrence of howling can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to audio equipment, P
The present invention relates to an acoustic transfer characteristic equalization device used in an equalizer for A or the like, a howling prevention device, or the like.

[0002]

2. Description of the Related Art An acoustic transfer characteristic equalizer has an analog filter or a digital filter arranged in front of a sound source.
It is a device that adjusts the frequency amplitude characteristic of the sound received by the sound receiver after passing through the transmission space having (z) to be equal to the frequency amplitude characteristic of the input signal from the sound source.
Therefore, an analog filter, a digital filter, or the like performs a correction process so that the frequency amplitude characteristic of the acoustic transfer characteristic becomes flat at all frequencies. In addition,
Hereinafter, the acoustic transfer characteristic equalizer is also simply referred to as an equalizer.

Further, although the following description will be given assuming that each signal is a discrete signal, the following description also applies when the signal is a continuous signal. In a discrete signal, the time representation of the signal is represented by, for example, x (k) with an integer parameter k representing time. Further, the frequency expression is expressed as X (z) by using z conversion. Hereinafter, the signal X (z) is also referred to as the input signal X (z).

FIG. 7 shows an acoustic transfer characteristic H (z) in a room.
It is an explanatory view for explaining. In FIG. 7, the indoor space 1
1 shows a case where a sound source 13 such as a speaker for inputting a signal from the input end 12 and a sound receiver 14 such as a microphone for outputting a signal at the output end 15 are installed.

When the signal X (z) is input to the input terminal 12 and the signal X (z) is output from the sound source 13,
The signal X (z) has an acoustic transfer characteristic H in the indoor space 11.
After being affected by (z), the sound receiver 14 is reached. The signal Y (z) received by the sound receiver 14 is output from the output end 15. Hereinafter, the signal Y (z) is also expressed as the output signal Y (z). The acoustic transfer characteristic H (z) is determined by the signal X (z) input to the input end 12 and the signal Y (z) at the output end 15.
It describes the input / output relationship between and, and is expressed as H (z) = Y (z) / X (z) (1). The acoustic transfer characteristics H (z) have different values even in the same indoor space if the spatial arrangements of the sound source 13 and the sound receiver 14 are different.

FIG. 8 is a block diagram showing a configuration for correcting the input signal X (z) so that the frequency-amplitude characteristic of the transfer characteristic becomes flat at all frequencies. The configuration shown in FIG. 8 differs from the configuration shown in FIG. 7 in that an equalizer 82 is provided at the input end 12. Input signal X
(Z) is input to the input terminal 81 of the equalizer 82.

The frequency amplitude characteristic of the equalizer 82 is F (z)
Then, if F (z) is equal to the inverse characteristic of the acoustic transfer characteristic H (z), the signal X ′ (output to the output end 15 when the input signal X (z) is input to the input end 81. The frequency amplitude characteristic of z) becomes equal to the frequency amplitude characteristic of the input signal X (z). That is, if the expression (2) is satisfied, the expression (3) is established.

| F (z) | = 1 / | H (z) | (2) | X ′ (z) | = | X (z) | (3) where || is the amplitude Represents a characteristic.

As a sound transmission characteristic equalizer which has been widely used in the past, there is one generally known by the name of a graphic equalizer or simply an equalizer. The equalizer is used in audio equipment or the like for reaching a sound receiving point without changing the tone color of a signal emitted from a sound source. FIG. 9 is a block diagram showing a configuration in which such an equalizer 91 is used as an equalizer 82.

As shown in FIG. 9, the equalizer 91 has a frequency band dividing unit 92 for dividing an input signal input to the input terminal 81 into frequency bands, and a gain adjusting unit 93 for each frequency band.
And a frequency band synthesis unit 94 that synthesizes the output of each gain adjustment unit 93.

The frequency band division unit 92 normally divides the input signal into signals of each frequency band by a band pass filter having a pass band of 1 octave or 1/3 octave width. Each gain adjusting unit 93 adjusts the gain of each frequency band so as to satisfy the expression (3). The adjusted signals in the respective frequency bands are combined by the frequency band combining unit 94 and supplied to the sound source 13.

An equalizer is used to prevent howling in a sound-expansion system involving a closed loop. Figure 10
FIG. 4 is an explanatory diagram for explaining a sound expansion system with a closed loop. In the sound expansion system, the voice of the speaker 101 is input to the sound receiver 14 and is amplified by the amplifier 103 so that the voice can be heard by the listener 102 with a sufficient volume. The output of the amplifier 103 is reproduced by the sound source 13.

Here, the sound emitted from the sound source 13 is heard by the listener 102 with a sufficient volume, and the sound transfer characteristic H
It is also input to the sound receiver 14 via (z). That is, a closed loop is formed. The signal input to the input terminal 12 between the amplifier 103 and the sound source 13 is X (z), and the sound receiver 14
The signal observed at the output end 15 between the sound source 13 and the sound source 13 is Y (z). From the input end 12, the sound source 13, the sound receiver 1
If G (z) is the transfer characteristic of the closed loop reaching the output end 15 via 4, the amplifier 103, the sound source 13, and the sound receiver 14, G
(Z) is expressed by equation (4).

G (z) = H (z) / (1−A · H (z)) (4) where A is the amplification factor of the amplifier 103. When the absolute value of G (z) exceeds 1 in the transfer characteristic of the closed loop, howling occurs at frequencies whose phases are 0, 360 °, 720 °, ..., 360 · n ° (n is an integer). However, howling can be prevented by suppressing the peak portion of the frequency amplitude characteristic of G (z) by the equalizer or the like in the closed loop transfer characteristic. FIG. 11 shows an equalizer 91 for the sound amplification system.
It is a block diagram which shows the structure which inserted. In addition, FIG.
14A to 14C are explanatory diagrams showing how the equalizer 91 that divides a signal into 12 frequency bands corrects the frequency-amplitude characteristic of the closed-loop transfer characteristic G (z).

The equalizer 91 is inserted, for example, between the input end 12 and the sound source 13. The frequency amplitude characteristic of each frequency band of the signal before suppression by the equalizer 91 is shown in FIG.
Suppose that it is as shown in 2. At that time, the equalizer 91 is set to have a band gain as shown in FIG. That is, the equalizer 91 corresponding to FIG.
The frequency-amplitude characteristic of is the inverse characteristic of the frequency-amplitude characteristic of the acoustic transfer characteristic corresponding to FIG. Therefore, the frequency amplitude characteristic of the transfer characteristic of the system including the equalizer 91 is as shown in FIG.
It is flattened as shown in FIG.

The gain of each band of the equalizer for flattening the frequency-amplitude characteristic of the transfer characteristic of the system including the equalizer is set by a human hand so that the input signal becomes white noise and the frequency characteristic of the received sound signal becomes flat. It is set by work or automatically.

[0017]

Generally, the acoustic transfer characteristic H (z) is different when the arrangement of the sound source 13 and the sound receiver 14 is different. Therefore, even if the equalizer 91 is adjusted to correct the frequency-amplitude characteristic of the transfer characteristic with respect to the positional relationship between a certain sound source 13 and the sound receiver 14, when the sound receiver 14 moves, the gain of each band of the equalizer 91 is restored. Need to be adjusted. Therefore, the equalizer 9 is used to prevent howling.
When 1 is used, each time the sound receiver 14 moves,
The equalizer adjusts the sound of the frequency that is likely to be howling by the ear, and adjusts the equalizer so that howling does not occur.
There is a problem that the gain in each frequency band of 1 must be readjusted.

The present invention has been made to solve such a problem. In a system in which a sound receiver or a sound source may be moved, if the equalizer is adjusted once, the equalizer is always kept as it is. It is an object of the present invention to provide an acoustic transfer characteristic equalizer that sets an environment in which howling is prevented and a sound faithful to a source sound can be received.

[0019]

An acoustic transfer characteristic equalizing apparatus according to the present invention includes a set of a sound source and a sound receiver arranged at a plurality of different positions in an acoustic system which is a target of frequency amplitude characteristic flattening. An acoustic transfer characteristic measuring unit that measures a plurality of acoustic transfer characteristics by using it, a pole estimating unit that estimates the poles of the acoustic system from each acoustic transfer characteristic measured by this acoustic transfer characteristic measuring unit, and this pole estimating unit estimates And an equalizer that equalizes a signal input to a sound source by using the poles of the acoustic system.

[0020]

Each acoustic transfer characteristic in a certain acoustic system includes a pole unique to that acoustic system. This peculiar pole gives the peak of the amplitude characteristic to the same frequency with respect to the frequency amplitude characteristic of each acoustic transfer characteristic. The pole estimation unit estimates a unique pole from each contribution amount of the unique pole given to each acoustic transfer characteristic. The equalizer equalizes the input signal so as to remove the influence of its unique pole.

[0021]

EXAMPLE As described above, each acoustic transfer characteristic in the same acoustic system commonly includes a pole peculiar to the acoustic system. Its unique pole is the resonance frequency and Q of the acoustic system.
Corresponds to the value. Hereinafter, this is called a common pole. The common pole gives the peak of the amplitude characteristic to the same frequency for a plurality of acoustic transfer characteristics in which the positional relationship between the sound source and the sound receiver is different. Therefore, according to the device having the characteristic of equalizing the common pole, it is possible to suppress the frequency amplitude characteristic peak common to a plurality of acoustic transfer characteristics.

The acoustic transfer characteristic equalizer according to the present invention is based on such an acoustical concept. Further, in the present invention, the contribution amount of the common pole is different in each acoustic transfer characteristic, and it is difficult to observe the common pole from a single acoustic transfer characteristic. presume.

FIG. 1 is an explanatory view for explaining the operation principle of the acoustic transfer characteristic equalizer according to the present invention. As shown in FIG. 1, consider a case where the equalizer 16 is provided between the input end 12 and the sound source 13 in the indoor space 11, and the sound receiver 14 is placed at each position in the indoor space 11. Sound source 13 and sound receiver 14
The arrangement relationship between and is represented as r _j (j = 1, 2, ..., M). FIG. 1 shows the case of M = 4.

Then, as disclosed in the specification of Japanese Patent Application No. 3-60538, each acoustic transfer characteristic H (r _j ,
z) is a common pole A (z) common to all acoustic transfer characteristics H (r _j , z), and B (r _j , z) having different characteristics when the sound source 13 and the sound receiver 14 are arranged differently. Is expressed by equation (5).

H (r _j , z) = B (r _j , z) / A (z) (5) (j = 1, 2, ..., M) This expression is common pole / zero. It is an expression of acoustic transfer characteristics called a model. If the characteristic of the common pole A (z) is supplied to the equalizer 16, the influence of the common pole is removed from the signal observed at each output terminal 15, that is, the peak of the common frequency-amplitude characteristic is suppressed. It becomes a signal. Hereinafter, H (r _j ,
z) is described as H _j (z).

FIG. 2 is a block diagram showing a configuration in which the acoustic transfer characteristic equalizer according to one embodiment of the present invention is arranged between the input end 12 and the indoor space 11. The equalization device 16 includes an acoustic transfer characteristic measuring unit 2 that measures each acoustic transfer characteristic H _j (z).
1, a pole estimator 22 that estimates the common pole A (z) from the measured acoustic transfer characteristics H _j (z), and an equalizer 23 that has the characteristics of the estimated common pole A (z). Have.

Next, the operation will be described. First, the sound source 13 and the sound receiver 1 are arranged in a plurality of different positional relationships as shown in FIG.
4 and 4 are arranged in the indoor space 11. In that state, the acoustic transfer characteristic measuring unit 21 measures each acoustic transfer characteristic H _j (z). For example, the acoustic transfer characteristic measuring unit 21 measures the impulse response to obtain each acoustic transfer characteristic H _j (z).

The pole estimation unit 22 is an acoustic transfer characteristic measurement unit 21.
From the acoustic transfer characteristics H _j (z) measured by the common pole A
Estimate (z). Hereinafter, each method of estimating the common pole A (z) will be described. Each method is disclosed in the specification of the above patent application. Also, in each method, the common pole A (z) is estimated in the form of a common AR coefficient that is an equivalent expression.

First, the first pole estimation method will be described. In this method, since each acoustic transfer characteristic H _j (z) has a common pole (that is, a common AR coefficient), the common AR coefficient is directly estimated from the input / output relationship of each characteristic with a least square error. Is. To obtain the common AR coefficient with the least square error, M impulse responses h (r _j , k) (j =
1, 2, ..., M) and the corresponding impulse response h _P (r _j , k) of the common pole-zero model ε
_The sum of squares of _out (r _j , k) should be minimized.

Impulse response h of the common pole / zero model
_P (r _j , k) is a unit impulse response δ
When it is (k), it is expressed by equation (6).

[0031]

[Equation 1]

Where a _i is the common AR corresponding to the common pole
The coefficient, b _i (r _j ) indicates the MA coefficient depending on the arrangement relation r _j between each sound source and the sound receiving point, P is the order of the common AR coefficient, and Q is the order of the MA coefficient. At this time, ε _out
(R _j , k) is represented by the equation (7).

[0033]

[Equation 2]

However, in general, the solution that minimizes this error
It is difficult to find. Therefore, h on the right side of equation (7)_P
(R_j, K) to h (r_j, K) replaced by the formula error ε_eq
(R _j, K) is introduced. ε_eq(R_j, K) is the expression (8)
It is represented by.

[0035]

[Equation 3]

Equation error ε for all r _j and k
_{When eq} (r _j , k) is expressed by a matrix, it becomes as shown in Expression (9).

[0037]

[Equation 4]

However,

[0039]

[Equation 5]

[0040]

[Equation 6]

[0041]

[Equation 7]

It is Here, N is the true impulse response length. When the equation (9) is expressed as e = h-Ax, 2 of e
The solution that minimizes the power norm is given by x = (A ^T A) ⁻¹ A ^T h (A ^T is a transposed matrix of A) (10). That is, if the equation (10) is calculated, the common AR coefficient a _i (i = 1, 2, ..., P) is obtained as a least squares solution.

Next, the second pole estimation method and the third pole estimation method will be described. These methods utilize the fact that the common pole of each acoustic transfer characteristic H _j (z) is emphasized by performing an averaging operation on a plurality of transfer characteristics.

According to the second pole estimation method, first, each AR coefficient a _i (r _j ) for each acoustic transfer characteristic H _j (z).
Calculate (i = 1, 2, ..., P). Each H _j (z)
The matrix representation of the equation error ε _eq (r _j , k) for is (11)
It becomes like a formula.

[0045]

[Equation 8]

Therefore, when the equation (11) is expressed as e = h-Ax, the solution that minimizes the squared norm of e is still x = (A ^T A) ^-1 A ^T h (12) ) Is given. That is, when the equation (12) is calculated, each AR coefficient a _i (r _j ) is obtained as a least squares solution.

Next, for each AR coefficient a _i (r _j ),
The average AR coefficient a _av ^' _i is obtained by performing the averaging operation expressed by the equation (13). Then, the obtained a _av ^' _i is used as the estimated value of the common pole. In this method, the calculation for pole estimation is simple.

[0048]

[Equation 9]

The third pole estimation method is for each acoustic transfer characteristic H _j.
After expanding each AR coefficient calculated in the same manner as in the second pole estimation method for (z) into an MA coefficient, the MA coefficient is averaged and the result is returned to the AR coefficient as a pole estimation value. Is the way to do it. AR estimated by this method
The transfer characteristic a _av ^' (z) of the coefficient is the acoustic transfer characteristic H
_When the denominator of _j (z) is represented as _A'j (z), (14)
It is related as shown in the formula.

[0050]

[Equation 10]

Although the third pole estimation method increases the amount of calculation as compared with the second pole estimation method, it is expected that the estimation error is small. The pole estimation unit 22 estimates the common pole by any method or another method. Either method causes an estimation error (for example, an error in a pole estimation value or an error in estimating a plurality of poles having close values as one representative pole), and the estimated pole and the physical pole are equal to each other. There are cases where you have not done so. However, it is possible to select a pole estimation method that poses no practical problem even if they do not match. Further, in estimating the common pole, the order of the MA coefficient may be 0.

The pole estimation unit 22 supplies the common AR coefficient a _i corresponding to the estimated common pole to the equalization unit 23. Equalizer 2
Reference numeral 3 is, for example, an FIR filter having the supplied common AR coefficient a _i as a filter coefficient. In that case, when the signal input to the input terminal 12 is x (k), the calculation by the equation (15) is performed, and y (k) is calculated as the sound source 13
Output to. At this time, the frequency amplitude characteristic of the signal received by the sound receiver 14 becomes substantially equal to that of the signal input to the input end 12.

[0053]

[Equation 11]

Next, description will be made of what kind of effect will be produced when the acoustic transfer characteristic equalizing apparatus according to the present invention is used for suppressing howling while the sound receiver is moving.
As shown in FIG. 3, consider a case where the sound receiver 14 moves at 16 points on the circumference around the sound source 13.

The results of computer simulation are shown below. Here, the size is 80 m ³ , and the reflectance of the wall is 95%.
The impulse response created by the computer simulation mirror image method was used assuming the room. The frequency band is 60 Hz to 320 Hz, and the reverberation time in the band is about 1.7 seconds.

First, when the sound receiving device 14 was placed at 9 of the 16 sound receiving device positions, the acoustic transfer characteristics were measured by the acoustic transfer characteristic measuring unit 21 at each position. Next, the acoustic transfer characteristic measuring unit 21 is caused to send the measured acoustic transfer characteristic to the pole estimating unit 22. The pole estimation unit 22 estimates the common pole as the common AR coefficient by the first pole estimation method. The order of the common pole was 200. Then, the common AR coefficient estimated by the pole estimation unit 22 is used as the equalization unit 2
3 was supplied.

FIG. 4 shows frequency amplitude characteristics. In the figure, the solid line shows the case where the acoustic transfer characteristic equalizer according to the present invention is applied, and the broken line shows the case where the acoustic transfer characteristic equalizer according to the present invention is not applied. As shown in the figure, according to the present invention, in particular, two sharp peaks around 100 Hz are suppressed.

FIG. 5 shows, for each of the 16 sound receiver positions, howling will occur for the first time when the acoustic transfer characteristic equalizing apparatus according to the present invention is applied, and howling will occur for the first time if not applied. It shows the result of comparison with the amplifier gain. However, first, the amplifier gain at which howling does not occur under all conditions was set as the reference gain (0 dB). Comparing the amplifier gains corresponds to comparing how much sound can be expanded without causing howling. The horizontal axis represents the position of the sound receiver 14.

When the acoustic transfer characteristic equalizer according to the present invention is not applied, for example, if the sound receiver 14 is located at the fifth position or the thirteenth position, howling occurs with an amplifier gain of about 1 dB. On the other hand, when the acoustic transfer characteristic equalizer according to the present invention is applied, the amplifier gain can be increased up to about 5 dB regardless of the position of the sound receiver 14.
This shows that the acoustic transfer characteristic equalizer according to the present invention suppresses the peak due to the resonance system common to the sound field.

As described above, when the acoustic transfer characteristic equalizing device according to the present invention is used, the frequency amplitude characteristic common to the acoustic transfer characteristics regarding a plurality of positional relationships between the sound source 13 and the sound receiver 14 is obtained. Peaks can be suppressed. As a result, once the setting of the equalizer 23 is completed, the sound receiver 14
Even if the is moved, howling is prevented.

Although the case of the acoustic transfer characteristic in the room has been described here, the present acoustic transfer characteristic equalizer is applied for the purpose of correcting the frequency amplitude characteristic of the speaker as the sound source in all directions, for example. You can also
FIG. 6 is a block diagram showing a case where the acoustic transfer characteristic equalizing device according to the present invention is applied as a frequency amplitude characteristic correction filter for a speaker.

As shown in the figure, the acoustic transfer characteristic measuring unit 21
Introduces signals from the plurality of sound receivers 14 placed in the anechoic chamber 61 and measures each acoustic transfer characteristic H _j (z). The sound receivers 14 are arranged in different directions from the speaker 63 whose frequency amplitude characteristic is to be corrected.

Since the acoustic transfer characteristics H _j (z) corresponding to the arrangement of the sound receivers 64 are those in the anechoic chamber 61, the speaker 63 has the same except for the effect of delay due to spatial propagation of sound. It is equal to the acoustic transfer characteristics for each direction. Therefore, the common pole estimated by the pole estimation unit 22 is a pole commonly included in the acoustic transfer characteristics of the speaker 63 for each direction, that is, the speaker 6
That is, the speaker characteristic does not depend on the directional characteristic 3 of FIG.

The common pole estimated by the pole estimation unit 22 is represented by A (z) as shown in the equation (5). The pole estimation unit 22 supplies A (z) to the equalization unit 23. As a result, when the speaker 63 is installed in another indoor space 11 and the input signal is passed through the equalizer 23 and the output of the equalizer 23 is supplied to the speaker 63,
The signal radiated from the speaker 63 becomes a signal from which the influence of the common pole of the acoustic transfer characteristics of the speaker 63 is removed at all locations in the indoor space 11.

[0065]

As described above, according to the present invention,
An acoustic transfer characteristic equalizer inputs to a sound source using a pole estimation unit that estimates a common pole of the acoustic system from each acoustic transfer characteristic measured by the acoustic transfer characteristic measurement unit and a common pole estimated by the pole estimation unit. Since it has a configuration that includes an equalizer that equalizes signals, it is possible to perform equalization on multiple acoustic transfer characteristics in the acoustic system collectively, and once in a loudspeaker system that involves the movement of a sound receiver. It is possible to provide a device that can prevent howling from occurring even if the sound receiver moves by setting the activating unit. When used as an equalizer for the acoustic transfer characteristic of the speaker, the acoustic transfer characteristic can be corrected without depending on the directivity characteristic of the speaker.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining an operation principle of an acoustic transfer characteristic equalizing device according to the present invention.

FIG. 2 is a block diagram showing an application example of the acoustic transfer characteristic equalization device according to the present invention.

FIG. 3 is an explanatory diagram showing experimental conditions for confirming the effect of the present invention.

FIG. 4 is an explanatory diagram showing frequency amplitude characteristics.

FIG. 5 is an explanatory diagram showing an amplifier gain in which howling occurs only when a sound receiver moves.

FIG. 6 is a block diagram showing another application example of the acoustic transfer characteristic equalization device according to the present invention.

FIG. 7 is an explanatory diagram for explaining an acoustic transfer characteristic H (z) in a room.

FIG. 8 is a block diagram for explaining the operation of the acoustic transfer characteristic equalizer.

FIG. 9 is a block diagram for explaining an operation of a conventional equalizer.

FIG. 10 is an explanatory diagram for explaining a sound expansion system with a closed loop.

FIG. 11 is a block diagram showing a configuration in which an equalizer is inserted in a sound expansion system.

FIG. 12 is an explanatory diagram showing frequency amplitude characteristics for each frequency band.

FIG. 13 is an explanatory diagram showing a gain for each frequency band of the equalizer.

FIG. 14 is an explanatory diagram showing a frequency amplitude characteristic of a transfer characteristic of a system including an equalizer.

[Explanation of symbols]

 16 Equalizer 21 Acoustic transfer characteristic measurement unit 22 Pole estimation unit 23 Equalization unit

Claims (1)

[Claims] 1. An acoustic transfer characteristic equalizer for flattening a frequency amplitude characteristic of an acoustic transfer characteristic from a sound source to a sound receiver, comprising: a plurality of different positions in an acoustic system to be subjected to the frequency amplitude characteristic flattening. From the acoustic transfer characteristic measurement unit that measures a plurality of acoustic transfer characteristics using each set of the arranged sound source and sound receiver, and the acoustic transfer characteristic measured by this acoustic transfer characteristic measurement unit, Equalizing unit for equalizing a signal input to the sound source by using the pole of the acoustic system estimated by the pole estimating unit. apparatus.