JP2010050500A - Rear surface noise-suppressing microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rear surface noise-suppressing microphone for suppressing rear surface noise over a broad frequencies. <P>SOLUTION: The rear surface noise-suppressing microphone 1 includes: a super-directivity microphone 2 having super-directivity; a microphone array 3 having a plurality of single-directivity microphones 4 having a single directivity arranged with a predetermined interval toward a rear surface direction, absorbing rear surface noise and outputting a signal; a microphone array signal-subtracting means 11 for subtracting signals outputted from a pair of previously set single-directivity microphones 4; a microphone array signal-shaping means 12 for shaping the signals subtracted by the microphone array signal-subtracting means 11 so as to match the frequency component of the rear surface noise; and a super-directivity microphone signal-subtracting means 13 for subtracting the signal shaped by the microphone array signal-shaping means 12 from a signal outputted from the super-directivity microphone 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a back noise suppression microphone that collects a target sound from the front direction and suppresses back noise that is a non-target sound from the back direction.

  Conventionally, when collecting sound outdoors, it is difficult to handle all situations with one type of microphone, so various types with directional characteristics such as omnidirectional, unidirectional, and superdirectivity are available. Microphones have been developed for different applications. Here, when using a microphone outdoors, it is rare that there is no sound other than the target sound. For this reason, shotgun microphones are widely used for outdoor sound collection, which uses a long acoustic tube to suppress noise from the side and collect sound from the front (target sound). (For example, product name: MKH-416, MKH-816, manufactured by Sennheiser Japan Co., Ltd.).

In addition, in order to suppress non-target sound (back noise) from the back direction, a small narrow angle directional microphone is known that combines a super-directional microphone and a secondary sound pressure gradient microphone in the back direction ( For example, see Patent Document 1).
JP 2005-323157 A

  However, although the above-mentioned shotgun microphone can suppress the non-target sound from the side direction, it does not suppress the non-target sound from the back direction (back noise). It is not suitable for collecting sound from the vehicle. Furthermore, since the noise generated by the user of the shotgun microphone is generated in the rear direction of the shotgun microphone, the shotgun microphone has a problem that this noise is also collected.

  The above-mentioned small narrow-angle directional microphone is intended to suppress the non-target sound from the back direction, but is intended for the mid-low range, and for example, the back side with many high frequency components such as applause. There is a problem that noise cannot be sufficiently suppressed.

  Accordingly, an object of the present invention is to provide a back noise suppression microphone that suppresses back noise over a wide frequency range.

  In order to solve the above-described problem, the back noise suppression microphone according to claim 1 is a back noise suppression microphone that collects the target sound from the front direction and suppresses the back noise that is a non-target sound from the back direction. A super directional microphone having super directivity as a directional characteristic, collecting a sound from the front direction and outputting a signal, and a unidirectional microphone having a uni directivity as a directional characteristic. A plurality of microphone arrays arranged at predetermined intervals in the rear direction, collecting the back side noise and outputting a signal, a microphone array signal subtracting means, a microphone array signal shaping means, and a super-directional microphone signal subtracting means And a configuration comprising:

  In such a configuration, the back noise suppression microphone collects the sound from the front, that is, the target sound generated by the target object, by the super-directional microphone. At this time, the backside noise suppression microphone collects backside noise that shows frequency characteristics with continuous peaks and valleys due to the back side characteristics of the super-directional microphone. Also, the back noise suppression microphone picks up back noise, which is a non-target sound, by a microphone array. The non-target sound is various noises generated by other than the target object.

  The backside noise suppression microphone subtracts signals output from a pair of preset unidirectional microphones in the microphone array by the microphone array signal subtracting means. Here, the frequency region of the back noise that can be suppressed differs depending on the interval at which the unidirectional microphones are arranged. That is, a pair of unidirectional microphones for subtracting signals are set in advance so that the back noise suppression microphone can suppress back noise.

  The backside noise suppression microphone shapes the signal subtracted by the microphone array signal subtracting unit by the microphone array signal shaping unit according to the frequency component in the back direction of the super-directional microphone. Here, since the back noise suppression microphone becomes a wave in which the frequency characteristics of the back noise are continuous by the microphone array signal shaping means, the signal subtracted by the microphone array signal subtraction means is shaped according to the waveform of each wave. . Then, the back noise suppression microphone subtracts the signal shaped by the microphone array signal shaping means, that is, the back noise, from the signal output from the super directional microphone by the super directional microphone signal subtracting means.

  Further, the back noise suppression microphone according to claim 2 is the back noise suppression microphone according to claim 1, wherein the unidirectional microphone of the microphone array has the acoustic direction of the superdirective microphone as a boundary in the front direction. The microphone array signal subtracting means is arranged in the rear direction, and the microphone array signal subtracting means is equidistant from the acoustic center as the frequency component of the back noise is lower, and is a pair of the unidirectionally arranged The signal output from the pair of unidirectional microphones that are equidistant from the acoustic center and closer to each other as the frequency component of the backside noise increases by subtracting the signal output from the directional microphone. It is characterized by subtracting.

  In such a configuration, the backside noise suppression microphone can prevent the occurrence of a phase shift because the microphone array signal subtracting unit uses the acoustic center as a reference.

  Further, the back noise suppression microphone according to claim 3 is the back noise suppression microphone according to claim 1 or claim 2, wherein the microphone array signal subtracting means is equal in number to the combination of the unidirectional microphones. The subtracting unit subtracts the signal output from the unidirectional microphone, and the microphone array signal shaping means includes a low-pass filter that passes a frequency component equal to or lower than a preset frequency, and a frequency equal to or higher than a preset frequency. The signal subtracted by the microphone array signal subtracting means is shaped by a high-pass filter that passes the component.

  In such a configuration, the backside noise suppression microphone can simplify the microphone array signal subtracting means and the microphone array signal shaping means.

According to the present invention, the following excellent effects can be obtained.
According to the first aspect of the present invention, the signals output from the unidirectional microphone capable of collecting the back noise are subtracted, and each of the back characteristics of the super-directional microphone for the front direction that becomes a mountain valley where the frequency characteristics are continuous is obtained. Since this signal is shaped in accordance with the waveform of the wave, the sensitivity to sound from the back direction can be suppressed and noise can be reduced over a wide frequency range.

According to the invention of claim 2, since the occurrence of phase shift can be prevented, it is possible to prevent a situation in which the backside noise cannot be suppressed.
According to the invention which concerns on Claim 3, a back surface noise suppression microphone can be made into a simple structure.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. In each embodiment, means and members having the same function are denoted by the same reference numerals, and description thereof is omitted.

[Backside noise suppression microphone configuration]
Hereinafter, the configuration of the back noise suppression microphone according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is an external view of a back noise suppression microphone according to an embodiment of the present invention. FIG. 2 is a schematic view schematically showing the back noise suppression microphone according to the embodiment of the present invention. The backside noise suppression microphone 1 of FIG. 1 collects sound from the front side and suppresses backside noise that is noise from the back side. The supersonic microphone 2, the microphone array 3, And control means 10. In FIG. 2, the right side of FIG. 2 is the front (front direction), and the left side of FIG. 2 is the back (back direction).

  The super-directional microphone 2 has super-directivity as a directivity characteristic, and collects sound from the front direction and the back-side noise and outputs a signal. For example, the diaphragm 2b is provided at the left end inside the acoustic tube 2a. Are arranged. Here, as the super-directional microphone 2, for example, there is a dynamic microphone having super directivity or a condenser microphone having super directivity.

The acoustic tube 2a is a hollow cylindrical body having a length of about 30 cm, for example, having a slit or a continuous hole (not shown) for suppressing side incoming sound formed on the side surface.
The vibration film 2b is disposed at the left end inside the acoustic tube 2a and captures vibrations of air. For example, the vibration film 2b is a metal film such as aluminum or geralumin, or a synthetic resin film such as polyethylene terephthalate. Further, the vibration of the vibrating membrane 2 b is converted into an electric signal by a sensor (not shown) and output to the control means 10.
The acoustic center 2c is the center position in the longitudinal direction (front direction to back direction) of the acoustic tube 2a.

  The cover 2d accommodates and protects the acoustic tube 2a, the vibrating membrane 2b, the microphone array 3 described later, and the control means 10 described later. As shown in FIG. 1, the cover 2d has a cylindrical shape in which the diameter on the front surface side is the same thickness as the diameter on the rear surface side, and a sound wave incident port is formed on the front surface in the front direction, and a slit is formed on the side surface. Yes. In FIG. 1, the acoustic tube 2a, the vibrating membrane 2b, the unidirectional microphone 4 and the control means 10 are not shown because they are accommodated in the cover 2d.

  Here, the super-directivity is a unidirectional characteristic that is easy to capture the sound in the front direction and further narrows the angle. FIG. 3 is a diagram illustrating an example of a polar pattern of the super-directional microphone of FIG. In FIG. 3, 0 ° corresponds to the front surface of FIG. 2, and 180 ° corresponds to the back surface of FIG.

  As shown in FIG. 3, the super-directional microphone 2 has a strong directivity in a range of about 60 ° with the front direction (0 °) as the center. For this reason, the super-directional microphone 2 rarely collects noise from the side direction (90 °, 270 °). However, the super-directional microphone 2 has sensitivity also in the back direction (180 °) as shown in FIG. That is, the super-directional microphone 2 collects back noise due to the sensitivity in the back direction.

The microphone array 3 in FIG. 2 has the polarities reversed so that n unidirectional microphones 4 ₁ , 4 _l , 4 _m , 4 _n (where 2 ≦ l ≦ m ≦ n) are differential. n unidirectional microphones 4 ₁ to 4 _n (secondary sound pressure tendency microphones) are arranged at a predetermined interval (for example, 4.25 cm). Note that when the unidirectional microphones 4 ₁ to 4 _n are described without being distinguished from each other, they are simply referred to as a unidirectional microphone 4.

  In the microphone array 3, n unidirectional microphones 4 are arranged in the front direction and the back direction, respectively, with the acoustic center 2 c of the superdirectional microphone 2 as a boundary. The microphone array 3 converts the sound picked up by the unidirectional microphone 4 into an electric signal and outputs it to the control means 10.

  As shown in FIG. 4, the unidirectional microphone 4 has unidirectionality as a directional characteristic, and is, for example, a microphone having a small diaphragm. FIG. 4 is a diagram illustrating an example of a polar pattern of the unidirectional microphone of FIG. In FIG. 4, 0 ° corresponds to the front surface of FIG. 2, and 180 ° corresponds to the back surface of FIG.

  Actually, the unidirectional microphone 4 is arranged with the sound receiving surface of a vibration film (not shown) of the unidirectional microphone 4 facing the back direction of the superdirectional microphone 2. For this reason, the unidirectional microphone 4 collects sound from the back direction (180 °), that is, back noise.

  Here, the back noise suppression microphone 1 is used in a differential manner by combining two unidirectional microphones 4, that is, as a secondary sound pressure gradient microphone. FIG. 5 is a diagram illustrating an example of a polar pattern of a secondary sound pressure gradient microphone obtained by combining the pair of unidirectional microphones 4 in FIG. In FIG. 5, 0 ° corresponds to the front surface of FIG. 2, and 180 ° corresponds to the back surface of FIG.

  As shown in FIG. 5, the secondary sound pressure gradient microphone (a pair of unidirectional microphones 4) has directivity in the front direction (0 °) and has little sensitivity in the back direction. For this reason, the secondary sound pressure gradient microphone can effectively collect only the back noise. The relationship between the interval between the unidirectional microphones 4 and the frequency characteristics will be described later.

  The control means 10 in FIG. 2 controls the back noise suppression microphone 1. Hereinafter, the configuration of the control means 10 will be described with reference to FIG. FIG. 5 is a block diagram showing the configuration of the control means of FIG.

<Configuration of control means of back noise suppression microphone>
As shown in FIG. 6, the control unit 10 includes a microphone array signal subtraction unit 11, a microphone array signal shaping unit 12, and a super-directional microphone signal subtraction unit 13.

The microphone array signal subtracting means 11 subtracts signals output from a pair of preset unidirectional microphones 4 (where 2 ≦ j ≦ k ≦ l ≦ m ≦ n) in the microphone array 3. is there. For example, in FIG. 6, and one first subtraction portion 11a subtracts the signal output by the unidirectional microphone 4 _n from the signal unidirectional microphone 4 ₁ outputs, unidirectional microphone 4 _j output and two second subtraction portion 11a unidirectional microphone 4 from a signal _m subtracts a signal output, a signal unidirectional microphone 4 _k unidirectional microphone from the signal output by the 4 _l outputs Although the third subtracting unit 11a to subtract is illustrated, the number of subtracting units 11a is not limited to this. For example, when the number of unidirectional microphones 4 is n, the maximum number of subtraction units 11a is a combination of n (not shown).

Here, the microphone array signal subtracting means 11 subtracts the signals output from the pair of unidirectional microphones 4 arranged at intervals such that the back noise can be suppressed by the subtracting unit 11a. For example, the microphone array signal subtracting means 11 is located at a distance from the acoustic center 2c and separated from the acoustic center 2c as the frequency component of the back noise becomes lower (for example, the sound of a cheering drum in a sports broadcast). The signals output from the unidirectional microphones 4 ₁ and 4 _n are subtracted.

Also, for example, the microphone array signal subtracting means 11 is equidistant from the acoustic center 2c and closer to each other as the frequency component of the background noise becomes higher by the subtracting unit 11a (for example, the sound of applause in sports broadcasting). A signal output from the pair of arranged unidirectional microphones 4 _l and 4 _m is subtracted.

Then, the microphone array signal subtracting unit 11 outputs the subtracted signal to the microphone array signal shaping unit 12. For example, when a pair of unidirectional microphones 4 ₁ , 4 _n is set in advance, the microphone array signal subtracting means 11 is connected to the unidirectional microphones 4 ₁ , 4 _n by a subtracting unit 11a. from the signals directional microphone 4 ₁ outputs, it subtracts the signal output by the unidirectional microphone 4 _n.

  The microphone array signal shaping means 12 shapes the signal subtracted by the microphone array signal subtracting means 11 according to the frequency component of the back noise. Further, the microphone array signal shaping means 12 measures the sensitivity of each unidirectional microphone 4 in advance, and based on this sensitivity, the sensitivity of the signal processed by the LPF 12a and the HPF 12b is substantially the same as that of the backside noise. The level may be adjusted so that Further, the microphone array signal shaping unit 12 outputs the shaped signal to the super-directional microphone signal subtracting unit 13.

  Further, the microphone array signal shaping means 12 can be configured by combining an LPF (low-pass filter) 12a and an HPF (high-pass filter) 12b so as to correspond to each of the subtracting units 11a. For example, FIG. 6 illustrates three sets of LPF 12a and HPF 12b, but the present invention is not limited to this. For example, the microphone array signal shaping means 12 can be configured by combining the same number of LPFs 12a and HPFs 12b as the subtracting unit 11a. Details of signal shaping by the microphone array signal shaping means 12 will be described later.

  Superdirective microphone signal subtracting means 13 subtracts the signal shaped by microphone array signal shaping means 12 from the signal output from superdirective microphone 2. Here, since the signal shaped in accordance with the back noise is subtracted from the signal output from the super directional microphone 2, the super directional microphone signal subtracting means 13 includes the back noise included in the signal output from the super directional microphone 2. Can be suppressed.

  The control means 10 may further include an amplifier, and the amplifier may amplify the signal output from the super-directional microphone signal subtraction means 13 (not shown). In this case, the control means 10 may perform the level adjustment described above after the signal is amplified by the amplifier.

<Details of signal shaping>
Details of the signal shaping by the microphone array signal shaping means 12 in FIG. 6 will be described below with reference to FIGS. 7 and 8 (see FIGS. 2 and 6 as appropriate). FIG. 7 is a diagram for explaining the details of the signal shaping by the microphone array signal shaping means of FIG. 6, and (a) is a diagram showing an example of the frequency characteristics of the back noise collected by the super-directional microphone. (b) is the figure which extracted the wave to the 1st dip, (c) is the figure which extracted the wave from the 1st dip to the 2nd dip. 7 and 8, the horizontal axis represents frequency (Hz) and the vertical axis represents sensitivity (dB).

As shown in FIG. 7A, the super-directional microphone 2 collects back noise, which is similar to a comb filter and has frequency characteristics with continuous peaks and valleys. Here, when the length of the acoustic tube 2a is L, dip (indentation) occurs at a frequency interval that satisfies the formula (1). This dip indicates that the sensitivity rapidly decreases at a certain frequency, and is shown like a valley in FIGS. In Equation (1), λ represents the wavelength of the back noise.
Formula (1): L = λ / 2, λ...

  Since this dip occurs at the above-described frequency interval, the super-directional microphone 2 collects sound as backside noise indicating frequency characteristics in which peaks and valleys are continuous. Thus, in the back noise, since the frequency characteristic in which the valleys are continuous is shown, the conventional technology can suppress the back noise only to the first dip as shown in FIG. 7B, and the effect is insufficient. It is thought that there was. Therefore, as shown in FIG. 7A, the present invention effectively suppresses the backside noise by treating the backside noise showing the frequency characteristics with continuous peaks and valleys as individual peaks and valleys by dividing them by dip. Made it possible.

  For example, the back noise in FIG. 7A is omitted from the peaks from the first dip to the second dip in FIG. 7C and the peaks from the first dip to the second dip in FIG. 7B. The peaks from the second dip to the third dip and the peaks from the (x−1) -th dip to the x-th dip (x is the number of dip) are omitted. Hereinafter, an example of suppressing the peaks from the first dip to the second dip in FIG. 7C among the back noise in FIG. 7A as back noise will be described.

  FIG. 8 is a diagram for explaining the details of signal shaping by the microphone array signal shaping means 12 of FIG. 6, and (a) is a diagram showing an example of frequency characteristics of a signal obtained by subtracting the outputs of a pair of unidirectional microphones. (B) is a diagram showing an example of the frequency characteristics of the signal shaped by the microphone array signal shaping means. Here, as shown in FIG. 8A, even in the signal obtained by subtracting the output of the pair of unidirectional microphones 4, dip occurs at different frequency intervals according to the interval between the pair of unidirectional microphones 4. appear. Therefore, a pair of unidirectional microphones 4 in which dips occur at substantially the same frequency intervals as in FIG. 7C are preset, and the microphone array signal subtracting means 11 outputs these unidirectional microphones 4. Subtract signal. Hereinafter, an example in which the microphone array signal subtracting unit 11 outputs a signal having the frequency characteristics shown in FIG. 8A to the microphone array signal shaping unit 12 will be described.

  The microphone array signal shaping unit 12 shapes the signal output from the microphone array signal subtracting unit 11, here, the signal shown in FIG. 8A to substantially the same frequency characteristics as the back noise shown in FIG. Specifically, the microphone array signal shaping unit 12 cuts a frequency region equal to or higher than the frequency at which the second dip is generated by the LPF 12a. Then, the microphone array signal shaping means 12 cuts a frequency region below the frequency at which the first dip is generated by the HPF 12b. Further, the microphone array signal shaping means 12 increases or decreases the signal obtained by cutting the frequency region to the same sensitivity as the back noise in FIG. 7C (level adjustment). Then, the microphone array signal shaping unit 12 outputs the shaped signal to the super-directional microphone signal subtracting unit 13.

  In addition, although the example which suppresses the peak from the 1st dip to the 2nd dip of FIG.7 (c) as a backside noise was demonstrated, the peak from the 2nd dip to the 3rd dip, and x-1th The peaks from the dip to the x-th dip are also suppressed as background noise. In this case, the backside noise suppression microphone 1 has a pair of unidirectional patterns so as to correspond to the peaks from the second dip to the third dip and the peaks from the (x−1) th dip to the xth dip. Each microphone 4 is set.

<Relationship between spacing of unidirectional microphone 4 and frequency characteristics>
Hereinafter, the relationship between the interval and the frequency characteristic of the unidirectional microphone 4 of FIG. 2 will be described with reference to FIG. 9 (see FIGS. 2 and 6 as appropriate). FIG. 9 is a diagram illustrating an example of frequency characteristics of a signal obtained by subtracting the outputs of a pair of unidirectional microphones. In FIG. 9, the horizontal axis represents frequency (Hz), and the vertical axis represents sensitivity (dB).

  As described above, the back noise suppression microphone 1 subtracts the signals output from the pair of unidirectional microphones 4. Here, when the interval between the unidirectional microphones 4 is D, the peak frequency fp at which the sensitivity is highest in the signal having the frequency characteristics as shown in FIG. 9 can be expressed as 340 / 2D, and the dip is lost. The frequency fd can be expressed as 340 / D. For example, when the interval D between the unidirectional microphones 4 is 10 cm, the peak frequency fp is 1.7 kHz and the dip frequency fd is 3.4 kHz.

  Further, for example, consider the case where the peak frequency fp is 2 kHz and the dip frequency fd is 4 kHz in the frequency characteristics of the super-directional microphone 2. In this case, in order to suppress the background noise, the unidirectional microphones 4 having the distances D between the unidirectional microphones 4 of 8.5 cm and 4.25 cm are set in advance, and the microphone array signal shaping means 12 The signal output from the unidirectional microphone 4 is subtracted.

[Operation of control means for back noise suppression microphone]
Hereinafter, the operation of the control means 10 of FIG. 6 will be described with reference to FIG. 10 (see FIG. 4 as appropriate). FIG. 10 is a flowchart showing the operation of the control means of FIG.

  First, the back noise suppression microphone 1 subtracts a signal output from a preset pair of unidirectional microphones 4 in the microphone array 3 by the microphone array signal subtraction unit 11. Here, the back noise suppression microphone 1 has a pair of unidirectivity that is equidistant from the acoustic center 2c and further away from each other as the frequency component of the back noise is lowered by the microphone array signal subtracting means 11. The signal output from the microphone 4 is subtracted, and the signal output from the pair of unidirectional microphones 4 that are equidistant from the acoustic center 2c and close to each other is subtracted as the frequency component of the back noise increases. (Step S11).

  Subsequent to the processing of step S11, the backside noise suppression microphone 1 uses the microphone array signal shaping unit 12 to shape the signal subtracted by the microphone array signal subtracting unit 11 according to the frequency component of the backside noise. Here, the back noise suppression microphone 1 performs a convolution operation between the LPF 12a and the HPF 12b by the microphone array signal shaping means 12, and shapes the signal subtracted by the microphone array signal subtraction means 11 (step S12).

  Subsequent to the processing in step S12, the rear noise suppression microphone 1 is subjected to level adjustment by the microphone array signal shaping means 12 shaped from the signal output from the superdirectional microphone 2 by the superdirectional microphone signal subtracting means 13. The signal is subtracted (step S13). As described above, the back noise suppression microphone 1 can suppress back noise over a wide frequency.

  Since the back noise suppression microphone according to the embodiment of the present invention suppresses back noise over a wide frequency range, it is possible to easily collect sound outdoors that has been difficult in the past. Furthermore, the back noise suppression microphone according to the embodiment of the present invention can collect sound by efficiently separating the sounds of each instrument in an environment where sound sources are dense, for example, in an orchestra.

It is an external view of the back surface noise suppression microphone which concerns on embodiment of this invention. It is the schematic diagram which showed typically the back surface noise suppression microphone which concerns on embodiment of this invention. It is a figure which shows the example of the polar pattern of the super-directional microphone of FIG. It is a figure which shows the example of the polar pattern of the unidirectional microphone of FIG. It is a figure which shows the example of the polar pattern of the secondary sound pressure gradient microphone which combined a pair of unidirectional microphone 4 of FIG. It is a block diagram which shows the structure of the control means of FIG. FIG. 7 is a diagram for explaining details of signal shaping by the microphone array signal shaping means of FIG. 6, (a) is a diagram showing an example of frequency characteristics of back noise collected by a super-directional microphone, and (b) is 1 It is the figure which extracted the peak to the 1st dip, (c) is the figure which extracted the peak from the 1st dip to the 2nd dip. It is a figure explaining the detail of the signal shaping by the microphone array signal shaping means 12 of FIG. 6, (a) is a figure which shows the example of the frequency characteristic of the signal which subtracted the output of a pair of unidirectional microphone, b) is a diagram showing an example of frequency characteristics of a signal shaped by the microphone array signal shaping means. It is a figure which shows the example of the frequency characteristic of the signal which subtracted the output of a pair of unidirectional microphone. It is a flowchart which shows operation | movement of the control means of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Back noise suppression microphone 2 Super directional microphone 2a Acoustic tube 2b Vibration membrane 2c Acoustic center 2d Cover 3 Microphone array 4 Unidirectional microphone 4 ₁ Unidirectional microphone 4 _l Unidirectional microphone 4 _m Unidirectional microphone 4 _n unidirectional microphone 10 control unit 11 microphone array signal subtraction unit 12 microphone array signal shaping means 13 super-directional microphone signal subtraction means

Claims (3)

A back noise suppression microphone that picks up the target sound from the front direction and suppresses back noise that is a non-target sound from the back direction,
A super-directional microphone that has super-directivity as a directional characteristic, collects sound from the front direction and outputs a signal;
A plurality of unidirectional microphones having a unidirectional directivity as a directional characteristic are arranged at predetermined intervals in the back direction, a microphone array that collects the back noise and outputs a signal;
A microphone array signal subtracting means for subtracting signals output from a preset pair of unidirectional microphones of the microphone array;
Microphone array signal shaping means for shaping the signal subtracted by the microphone array signal subtracting means in accordance with the frequency component of the back noise;
Superdirective microphone signal subtracting means for subtracting the signal shaped by the microphone array signal shaping means from the signal output by the superdirective microphone;
A back noise suppression microphone, comprising: The unidirectional microphones of the microphone array are respectively arranged in the front direction and the back direction with the acoustic center of the superdirectional microphone as a boundary,
The microphone array signal subtracting unit subtracts signals output from the pair of unidirectional microphones that are equidistant from the acoustic center and spaced apart from each other as the frequency component of the back noise decreases. The signal output from the pair of unidirectional microphones that are equidistant from the acoustic center and close to each other as the frequency component of the back noise increases is subtracted. 2. A back noise suppression microphone according to 1. The microphone array signal subtracting means subtracts the signal output from the unidirectional microphone by a subtracting unit equal in number to the number of combined unidirectional microphones,
The microphone array signal shaping means is subtracted by the microphone array signal subtracting means by a low-pass filter that passes a frequency component equal to or lower than a preset frequency and a high-pass filter that passes a frequency component equal to or higher than a preset frequency. The back noise suppression microphone according to claim 1 or 2, wherein the signal is shaped.

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