JP3146804B2 - Array microphone and its sensitivity correction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array microphone used as one of directional microphones and a sensitivity correction device used for the array microphone.

[0002]

2. Description of the Related Art In recent years, array microphones have been used for high S / N sound pickup in remote sound pickup and howling prevention of loudspeakers because of their extremely sharp directivity.

Hereinafter, an example of the above-described array microphone will be described with reference to the drawings.

FIG. 6A shows a configuration of a conventional array microphone. In FIG. 6, 61 is a first microphone unit, 62 is a second microphone unit, and 63 is an Nth microphone unit. Reference numeral 64 denotes a microphone array, and the first microphone unit 6
The first to N-th microphone units 63 are configured by a one-dimensional array of N units having the same characteristics. 65 is a directivity forming means, and 66 is an output terminal.

The operation of the array microphone configured as described above will be described below. First, the first microphone unit 61 to the Nth microphone unit 63 receive incoming sound waves,
5 is output. The directivity forming unit 65 forms a desired directivity by using a change in the phase difference between the output signals of the microphone units according to the incident angle when the plane wave is incident on the microphone array 64. Hereinafter, an example of the directivity forming unit 65 will be described with reference to the drawings.

For example, in the directivity forming means shown in FIG. 6B, the first signal input terminal 67 to the Nth signal input terminal 6
9 to the output signal of each microphone unit input to
Weighting such as Chebyshev is performed by the signal amplifiers 610 to 612, and the directivity is formed by adding the respective signals by the adder 613. As a result, at the signal output terminal 614, a directional characteristic is obtained in which the maximum sensitivity (front direction) is at 90 ° with respect to the arrangement direction of the microphone array units.

In the array microphone described in Japanese Patent Application Laid-Open No. 2-205200, as shown in FIG. 6C, a digital filter provided at the subsequent stage of each unit and having the same number of taps as the number of microphone units is provided. 615-617, and a fan filter [e.g. El. Peacock: “On the Practical Design of Discrete Velocity
Filters for Seismic Data Processing, ”
ANS. A.C.A.U.S.T.S., S.P.E.E.C.E.H. and S.I.A.N.E.N.P.R.E.R.O.C.E.S.S.S. , AS SP-30, 1, PP. 52-60 (FE
Bee. 1982). ｛KLPeacock: On the practical desig
n of discrete velocity filters for seismic data pr
ocessing ", IEEE Trans.Acoust., Speech & Signal Proc
ess., ASSP-30, 1, pp. 52-60 (Feb. 1982).}] is used as the directivity forming means. As a result, the output of the signal output terminal 614 has a sharper cut-off characteristic at the boundary between the blind spot area and the sound pickup area than the directivity forming means shown in FIG. A uniform sound pressure frequency characteristic can be obtained for the angle.

[0008]

However, usually,
Since the directivity forming means of the array microphone is designed on the assumption that all the input signal levels are equal, the sensitivity of each microphone unit constituting the array microphone and the sensitivity of a circuit such as a microphone amplifier attached thereto ( In the following, when these are collectively referred to simply as the sensitivity of the microphone unit), the signal level of each unit varies at the input part of the directivity forming unit, and the directional characteristics are not uniform. Had a problem of deterioration. In addition, it is difficult to prepare a large number of microphone units and circuits having completely the same characteristics due to the manufacturing method, and an array microphone that can obtain desired directional characteristics even if the sensitivity slightly varies is desirable.

In view of the above problems, the present invention provides an array microphone having a function of automatically correcting the sensitivity of each microphone unit constituting an array microphone to have the same characteristics, and a sensitivity correction device for automatically correcting the sensitivity. It is intended to do so.

[0010]

In order to solve the above-mentioned problems, an array microphone according to the present invention comprises: a microphone array comprising at least two or more first to Nth microphone units; To (N
-1) first to (N-1) th sensitivity correction devices provided at the subsequent stage of each of the microphone units;
To the (N-1) th sensitivity correction device and the Nth
And a directivity forming unit that receives an output signal of the microphone unit of (a) as an input. The first to (N−1) th sensitivity correcting units refer to the output signal of the Nth microphone unit. The sensitivity of each microphone unit so that the level of each output signal from the first sensitivity correction device to the (N-1) th sensitivity correction device is equal to the signal level from the Nth microphone unit. The correction is performed.

[0011]

According to the present invention, the microphone array is used as a reference input to a sensitivity correction device provided at the subsequent stage of each microphone unit other than the reference microphone unit. By matching the sensitivity characteristics of each microphone unit to be formed, deterioration of the directional characteristics of the array microphone is suppressed.

[0012]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an array microphone according to an embodiment of the present invention. In FIG. 1, 11
Is a first microphone unit, 12 is a second microphone unit, 13 is an (N-1) th microphone unit, and 14 is an Nth microphone unit. Fifteen
Is a microphone array in which first to Nth microphone units 11 to 14 are linearly arranged. Reference numeral 16 denotes a first sensitivity correction device, which is provided after the first microphone unit 11. An embodiment of the sensitivity correction device will be described later. Similarly, reference numerals 17 and 18 denote second and (N-1) th sensitivity correction devices, respectively, which are the second microphone unit 1 respectively.
2. It is provided at the subsequent stage of the (N-1) -th microphone unit 13. Further, each of the sensitivity correction devices from the first sensitivity correction device 16 to the (N-1) th sensitivity correction device 18 uses the output signal of the Nth microphone unit 14 as a reference signal. 19 is a directivity forming means, and 110 is a signal output terminal.

The operation of the array microphone configured as described above will be described below.

The sound waves picked up by the microphone array 15 are output to the subsequent stage via the first to Nth microphone units 11 to 14. From the first sensitivity correction device 16 to the (N-1) th sensitivity correction device 18, the output signal of the Nth microphone unit 14 is input as a reference signal, and the level of each output signal is output from the Nth microphone unit 14. So that it is equal to the signal level
The sensitivity of each microphone unit is corrected. As a result, even when the sensitivity of the microphone unit varies, the level of the input signal to the directivity forming means 19 becomes equal, and the deterioration of the directivity characteristics in the directivity forming means 19 can be suppressed.

The array microphone 250 according to the present embodiment
FIG. 5 (a) shows the directional characteristics at Hz, 500Hz and 1kHz, and FIG.
This is shown in FIG. As is clear from both figures, the array microphone according to the present embodiment can obtain a larger attenuation of sensitivity particularly from the side to the back than the conventional array microphone, and the directional characteristics are improved.

As described above, according to the present embodiment, at least two of the first to Nth microphone units and the first to (N-1) th microphone units are provided at the subsequent stages. A first to (N-1) th sensitivity correction device; and a directivity forming unit that receives an output signal of the first to (N-1) th sensitivity correction device and an output signal of the Nth microphone unit as inputs. With this arrangement, it is possible to suppress the deterioration of the directivity characteristics due to the variation in the sensitivity of each microphone unit.

An embodiment of the sensitivity correction device according to the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram of one embodiment of the sensitivity correction device according to the present invention. In FIG. 2, 21 is a signal input terminal, 22 is a reference signal input terminal, 23 and 24 are first and second absolute value calculation means for calculating the absolute value of the signal, and 25 is a subtraction for subtracting two signals. Means, 26 is a code detecting means for detecting the sign of the signal, 27 is a multiplying means for multiplying the signal by a constant, 28 is a variable signal amplifying means for amplifying or attenuating the input signal according to the output signal of the multiplying means 27,
9 is a signal output terminal.

The operation of the sensitivity correction device configured as described above will be described below. The first to (N-1) th microphone units 1 input to the signal input terminal 21
The signals from 1 to 13 are output by the variable signal amplifying means 28.
The control signal from the multiplying means 27 is amplified or attenuated in accordance with the sign of the control signal, and the amount of amplification and attenuation is determined by the magnitude of the control signal. The signal amplified or attenuated by the variable signal amplifier 28 is output from a signal output terminal 29.
The output signal of the variable signal amplifying means 28 is also output to the absolute value calculating means 23, and the absolute value calculating means 23 calculates the absolute value.

On the other hand, the absolute value of the reference signal input from the reference signal input terminal 22 is calculated by the absolute value calculating means 24. The subtraction means 25 subtracts the output signal of the absolute value calculation means 23 from the output signal of the absolute value calculation means 24.
The sign of the output of the subtracting means 25 is output by the sign detecting means 26, that is, +1 when the output of the subtracting means 25 is positive and -1 when the output of the subtracting means 25 is negative. The output of the sign detecting means 26 is multiplied by a constant by the multiplying means 27, and the control signal to the variable amplifying means 28 is updated.

More specifically, if the absolute value of the reference signal is larger than the absolute value of the signal corrected by the variable amplifying means 28, the output of the subtracting means 25 becomes positive and the sign detecting means outputs +1. , The control signal increases. Conversely, if the absolute value of the reference signal is smaller than the absolute value of the signal corrected by the variable amplifying means 28, the sign detection means outputs -1 and the control signal decreases. The update width of the control signal is determined by the constant of the multiplication means 27.

As described above, according to the magnitude of the reference signal and the output signal of the variable signal amplifying means 28, the variable signal amplifying means 28
When this operation is repeated to update the control signal for determining the amplification factor, the amplification factor of the variable amplification unit converges so that the level difference between the output signal of the variable signal amplification unit 28 and the reference signal is minimized. By repeating this operation, a signal having the same level as the reference signal can be obtained from the signal output terminal.

As described above, according to this embodiment, the signal input terminal to which the signal to be corrected is input, the reference signal input terminal to which the reference signal is input, and the absolute value of the signal are calculated. First and second absolute value calculating means, subtracting means for subtracting two signals, sign detecting means for detecting the sign of the signal, multiplying means for multiplying the signal by a constant, and converting the signal according to the control signal Variable signal amplification means for amplifying or attenuating,
A signal output terminal for outputting a signal amplified or attenuated by the variable signal amplifying means, wherein the signal input terminal is connected to an input section of the variable signal amplifying means, and an output of the variable signal amplifying means is the signal output terminal. And the input of the first absolute value calculating means, and the reference signal input terminal is connected to the second absolute value calculating means.
Are connected to the inputs of the absolute value calculating means, and the outputs of the first absolute value calculating means and the second absolute value calculating means are connected to the inputs of the subtracting means. An output signal of the first absolute value calculation means is subtracted from the output signal, an output of the subtraction means is connected to an input of the multiplication means, and the multiplication means outputs a control signal to the variable signal amplification means, The levels of the input signal and the reference signal can be matched.

Hereinafter, another embodiment of the sensitivity correction apparatus according to the present invention will be described with reference to the drawings.

FIG. 3 shows a second example of the sensitivity correction device according to the present invention.
FIG. 4 is a block diagram of an embodiment of FIG. The configuration shown in FIG. 3 is basically the same as that shown in FIG. 2, and components having the same functions as those in FIG. 2 are denoted by the same reference numerals and description thereof is omitted. The difference between the configuration of FIG. 3 and the configuration of FIG.
Are provided before the absolute value calculating means 23 and 24, respectively.

In the case where an offset voltage is applied to the output signals of the microphone units 11 to 13, the sensitivity correction device of the first embodiment corrects the sensitivity including the offset voltage. In some cases, the sensitivity may not be corrected correctly. Therefore,
The sensitivity correction device of the present embodiment is provided with an offset removal device,
By removing the offset component included in the input signal and the reference signal, it is possible to suppress the adverse effect of the offset component on the sensitivity correction amount.

As described above, according to the present embodiment, the offset correction means is provided before each of the first absolute value calculation means and the second absolute value calculation means of the sensitivity correction device, so that the output from the microphone unit is obtained. The influence of the offset voltage on the sensitivity correction amount can be suppressed.

Hereinafter, another embodiment of the sensitivity correction apparatus according to the present invention will be described with reference to the drawings.

FIG. 4 shows a third example of the sensitivity correction device according to the present invention.
FIG. 4 is a block diagram of an embodiment of FIG. The configuration shown in FIG. 4 is basically the same as that shown in FIG. 2. Components having the same functions as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted. The difference between the configuration of FIG. 4 and the configuration of FIG.
Are provided with bandpass filters 43 and 44 in front of the absolute value calculating means 23 and 24, respectively.

When the wavelength of an incoming sound wave is sufficiently short with respect to the size of hardware such as a housing constituting a microphone array, the sound pressure collected by each microphone unit may vary due to the sound wave diffraction phenomenon. . When sensitivity correction is performed in such a case, the operation of correcting the original variation in sensitivity of the microphone unit is alienated. Therefore, in the sensitivity correction device of the present embodiment, a band-pass filter is provided, and a signal in a frequency band where a diffraction phenomenon occurs is removed from an input signal and a reference signal at the time of sensitivity correction, so that the effect of the diffraction phenomenon on the sensitivity correction amount is reduced. Can be suppressed.

As described above, according to this embodiment, the diffraction phenomenon of the arriving sound wave is corrected for sensitivity by providing the band-pass filters in front of each of the first absolute value calculating means and the second absolute value calculating means. The effect on the quantity can be eliminated.

Note that the array microphone of the present invention is not limited to the above-described embodiment. For example, the first and second embodiments of the sensitivity correcting apparatus described above are combined with each other to combine the first and second embodiments. It is also possible to provide an offset removing means and a band-pass filter before the absolute value calculating means 23 and 24.

[0034]

As described above, in the array microphone of the present invention, the first to (N-1) th sensitivity correction devices are provided after the first to (N-1) th microphone units. The output signal of the N microphone units is input from the first sensitivity correction device as a reference signal of the (N-1) th sensitivity correction device, and the output signal of the (N-1) th sensitivity correction device is input from the first sensitivity correction device. By correcting the sensitivity of each microphone unit so that the level of each output signal becomes equal to the signal level from the Nth microphone unit, it is possible to suppress deterioration of the directivity due to variations in the sensitivity of the microphone units. And a sensitivity correction device used for the array microphone.

[Brief description of the drawings]

FIG. 1 is a block diagram of an array microphone according to an embodiment of the present invention.

FIG. 2 is a block diagram of a first embodiment of a sensitivity correction device according to the present invention.

FIG. 3 is a block diagram of a second embodiment of the sensitivity correction device according to the present invention;

FIG. 4 is a block diagram of a third embodiment of the sensitivity correction device according to the present invention.

5A is a diagram showing directivity characteristics of an array microphone according to an embodiment of the present invention; FIG. 5B is a diagram showing directivity characteristics of an array microphone according to a conventional example;

6A is a block diagram of a conventional array microphone. FIG. 6B is a block diagram showing an example of a conventional directivity forming unit. FIG. 6C is a block diagram showing another example of a conventional directivity forming unit.

[Explanation of symbols]

 Reference Signs List 11 first microphone unit 12 second microphone unit 13 (N-1) th microphone unit 14 Nth microphone unit 15 microphone array 16 first sensitivity correction device 17 second sensitivity correction device 18th (N− 1) Sensitivity correction device 19 Directivity forming means 21 Signal input terminal 22 Reference signal input terminal 23 First absolute value calculation means 24 Second absolute value calculation means 25 Subtraction means 26 Sign detection means 27 Multiplication means 28 Variable signal amplification Means 29 Output signal terminal 33 First offset removing means 34 Second offset removing means 43 First bandpass filter 44 Second bandpass filter 110 Signal output terminal

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Satoru Ibaraki 1006 Kazuma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-5-227589 (JP, A) JP-A-59- 70097 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04R 3/00 320 H04R 1/40 320

Claims (7)

(57) [Claims] 1. A microphone array comprising at least two or more first to Nth microphone units, and a first to a (N-1) th microphone unit provided at a subsequent stage of each of the first to (N-1) th microphone units. To (N-
1) a sensitivity correction device, and directivity forming means for inputting output signals of the first to (N-1) th sensitivity correction devices and an output signal of the Nth microphone unit,
The (N-1) th sensitivity correction device to the (N-1) th sensitivity correction device input the output signal of the Nth microphone unit as a reference signal, and receive the (N-
An array microphone wherein the sensitivity of each microphone unit is corrected so that the level of each output signal of the sensitivity correction device of 1) is equal to the signal level from the Nth microphone unit. 2. A sensitivity correction device comprising: a signal input terminal to which a signal output from a microphone unit is input; a reference signal input terminal to which a reference signal is input; and first and second signals for calculating an absolute value of the signal. Second absolute value calculating means, subtracting means for subtracting two signals, sign detecting means for detecting the sign of the signal, multiplying means for multiplying the signal by a constant, and amplifying or attenuating the signal according to the control signal Variable signal amplifying means, and a signal output terminal for outputting a signal amplified or attenuated by the variable signal amplifying means to the directivity forming means, wherein the signal input terminal is connected to an input of the variable signal amplifying means. Connected, the output of the variable signal amplifying means is connected to the signal output terminal and the input of the first absolute value calculating means, and the reference signal input terminal is connected to the input of the second absolute value calculating means. Outputs of the first absolute value calculating means and the second absolute value calculating means are connected to an input of the subtracting means, and the subtracting means calculates the first absolute value from an output signal of the second absolute value calculating means. The output signal of the value calculation means is subtracted, an output of the subtraction means is connected to an input of the multiplication means, and the multiplication means outputs a control signal to the variable signal amplification means. Array microphone. 3. The array microphone according to claim 2, wherein offset removing means is provided at a stage preceding each of said first absolute value calculating means and said second absolute value calculating means. 4. The array microphone according to claim 2, wherein a band-pass filter is provided before each of said first absolute value calculating means and said second absolute value calculating means. 5. A signal input terminal for inputting a signal to be corrected, a reference signal input terminal for inputting a reference signal, and first and second absolute value calculation for calculating an absolute value of the signal. Means, subtraction means for subtracting the two signals, sign detection means for detecting the sign of the signal, multiplication means for multiplying the signal by a constant, and variable signal amplification means for amplifying or attenuating the signal according to the control signal. A signal output terminal for outputting a signal amplified or attenuated by the variable signal amplifying means, wherein the signal input terminal is connected to an input of the variable signal amplifying means, and an output of the variable signal amplifying means is the signal An output terminal is connected to an input of the first absolute value calculating means, and the reference signal input terminal is connected to an input of the second absolute value calculating means, and the first absolute value calculating means and the second absolute value calculating means are connected to each other. Absolute value calculation means The force is connected to the input of the subtraction means, and the output signal of the first absolute value calculation means is subtracted from the output signal of the second absolute value calculation means by the subtraction means, and the output of the subtraction means is multiplied by the multiplication. The sensitivity correction device is connected to an input of a means, and the multiplying means outputs a control signal to the variable signal amplifying means. 6. The sensitivity correction device according to claim 2, wherein offset removing means is provided at a stage preceding each of said first absolute value calculating means and said second absolute value calculating means. 7. The sensitivity correction device according to claim 2, wherein a band-pass filter is provided before each of said first absolute value calculating means and said second absolute value calculating means.