JP7075188B2 - Video camera with directional microphone and variable directional microphone - Google Patents

Description

The present invention relates to a directional microphone capable of suppressing the directional sensitivity of the back surface or the side surface, or a combination thereof, and a video camera with a variable directional microphone.

As a prior art, there is a narrow directional microphone using a line microphone having a single acoustic tube alone. This narrow directional line microphone tends to have a wide directivity in a low frequency band and tends to have a tendency that the back sensitivity characteristic is not easily suppressed.

Therefore, in order to improve the tendency that the back sensitivity characteristic is hard to be suppressed, a line microphone having an acoustic tube and a directional microphone for suppressing the back sensitivity are combined to provide an excellent back surface over the entire audible frequency band. Backside sensitivity suppression type narrow directional microphones that realize sensitivity suppression are already known (see, for example, Patent Documents 1 and 2).

By the way, a video camera with a variable directivity microphone that can change the directivity of a microphone according to a zoom is known (see, for example, Patent Documents 3 and 4).

A video camera usually has an optical zoom function, and can take a close-up shot of a subject located in front of the video camera. At this time, according to the techniques of Patent Documents 3 and 4, it is possible to suppress ambient noise other than the sound emitted by the subject in accordance with the close-up of the subject of interest at the time of collecting the sound recorded at the same time as the video.

Japanese Patent No. 5268713 Japanese Patent No. 4383242 Japanese Patent No. 2500888 Japanese Patent No. 2900722

The conventional back-sensitivity suppression type narrow-directional microphone as disclosed in Patent Documents 1 and 2 has a low-pass filter for the output signal of the line microphone having an acoustic tube and the output signal of the back-sensitivity suppression directional microphone. By adding or subtracting the one whose band is limited by using it, the back sensitivity of the line microphone having an acoustic tube is suppressed.

In this case, when the sound is incident from the back side, the relationship between the output signal of the line microphone and the output signal of the microphone for suppressing back sensitivity that has passed through the low-pass filter has approximately the same amplitude, and the addition processing is performed as the subsequent processing. In some cases, it cannot be suppressed with high accuracy unless it is in the opposite phase relationship (in the case of the subtraction process, it is not in the same phase relationship).

However, since the relationship between the amplitude and the phase of each of these output signals changes for each frequency, when a simple low-pass filter is used, the band that can be suppressed with high accuracy may be limited.

Further, by adding or subtracting the output signal of the microphone for suppressing the back sensitivity, even if the sensitivity in the back direction is reduced, the sensitivity of the undesired side surface may be increased.

It is possible to configure a microphone that suppresses not only the back surface of the microphone but also the back surface or the side surface, or a combination of these in the directivity direction, and in that case as well, the band that can be suppressed with high accuracy is limited. there is a possibility.

In particular, in a video camera with a variable directivity microphone that allows the directivity of the microphone to be changed according to the zoom, it is preferable to suppress the sensitivity of both the rear surface and the side surface with high accuracy according to the zoom.

Therefore, a directional microphone and a video camera with a variable directional microphone are desired, which suppress the sensitivity of the desired back surface or side surface, or a combination thereof in the directional direction with high accuracy in a wide band.

In view of the above problems, an object of the present invention is to provide a directional microphone that suppresses sensitivity in a predetermined directional direction with high accuracy in a wide band, and a video camera with a variable directional microphone.

The directional microphone of the first aspect according to the present invention is a directional microphone having anterior narrow directionalness with suppressed back sensitivity, and is a main microphone having anterior narrow directional direction using an acoustic tube, and the acoustic tube. For at least one sub-microphone arranged along the longitudinal direction and having unidirectionality in the direction opposite to the front direction forming the main axis of the anterior narrow directional, and each output signal obtained from the at least one sub-microphone. , The filtered signal that cancels the response on the back surface of the main microphone and the signal that has been delayed processed so as to compensate for the delay amount generated by the filtering process are added to the output signal obtained from the main microphone. The signal processing unit includes a signal processing unit that generates a sound pickup signal with suppressed back sensitivity, and the signal processing unit includes an output signal vector M (ω) after delay processing of the main microphone and a transmission function of the filter processing. The front narrow directional main axis θ = 0 ° obtained by adding the digital output signal obtained by filtering the output signal vector G (ω) of the at least one sub-microphone by the vector W (ω). The final output vector Y (ω) at an arbitrary frequency ω from the front direction to the back direction, which makes θ = 180 °, and θ = 180 °, while maintaining the sensitivity in the front direction, which makes θ = 0 °. The difference between the final output vector Y (ω) and the target characteristic vector D (ω) is minimized based on a predetermined norm by using the target characteristic vector D (ω) for suppressing the sensitivity in the back direction. It is characterized in that it is subjected to a filtering process .

Further, the directional microphone of the third aspect according to the present invention is a directional microphone having a donut-shaped directivity, which is a pair of unidirectional microphones brought close to each other with opposite directivity directions and the pair. An omnidirectional microphone having omnidirectionality arranged between unidirectional microphones, a signal obtained by filtering the pair of unidirectional microphones, and a filtered signal to the omnidirectional microphone. It is characterized by comprising a signal processing unit that generates a sound pickup signal having a donut-shaped directivity by performing a predetermined addition / subtraction process using the signal.

Further, the directional microphone of the fourth aspect according to the present invention is a directional microphone having anterior narrow directional with suppressed side sensitivity, and a main microphone having an anterior narrow directional using an acoustic tube and the acoustic. A pair of unidirectional microphones arranged along the longitudinal direction of the tube and brought close to each other in opposite directions that are the same direction and opposite to each other with respect to the front direction forming the anterior narrow directional main axis. For each output signal obtained from the omnidirectional microphones arranged between the pair of unidirectional microphones, the pair of unidirectional microphones, and the omnidirectional microphones. A filtered signal that cancels the lateral response of the microphone and a delay-processed signal that compensates for the delay amount caused by the filter processing are added to the output signal obtained from the main microphone. It is characterized by including a signal processing unit that generates a sound collecting signal with suppressed side sensitivity.

Further, in the directional microphone of the fourth aspect according to the present invention, the signal processing unit has the output signal vector M _side (ω) after the delay processing of the main microphone and the transmission function vector W _side (ω) of the filtering processing. The front narrow directional spindle obtained by adding a digital output signal obtained by filtering the output signal vector G _side (ω) of the pair of unidirectional microphones and the omnidirectional microphone. The final output vector Y (ω) at an arbitrary frequency ω in the front direction where θ = 0 °, the side direction where 0 ° << | θ | <180 °, and the back direction where θ = 180 °, and θ = Target characteristic vector for suppressing the sensitivity in the side direction that makes 0 ° << | θ | <180 ° while maintaining the sensitivity in the front direction that makes 0 ° and the sensitivity in the back direction that makes θ = 180 °. It is characterized in that D _side (ω) is used to perform a filtering process that minimizes the difference between the final output vector Y (ω) and the target characteristic vector D _side (ω) based on a predetermined norm.

Further, the directional microphone of the fifth aspect according to the present invention is a directional microphone having anterior narrow directional with suppressed back and side sensitivity, and a main microphone having an anterior narrow directional using an acoustic tube. A pair of unidirectional objects arranged along the longitudinal direction of the acoustic tube and approaching each other in the same direction and opposite directions to the front direction forming the main axis of the anterior narrow directionality. An omnidirectional microphone arranged between the pair of unidirectional microphones, an omnidirectional microphone arranged along the longitudinal direction of the acoustic tube, and a frontal direction forming the main axis of the anterior narrow directionalness. For each output signal obtained from the unidirectional sub-microphone pointing in the direction opposite to the unidirectional microphone, the pair of unidirectional microphones, the omnidirectional microphone, and the sub-microphone. A filtered signal that cancels the side-to-side and back-side responses of the microphone, and a delay-processed signal that compensates for the amount of delay caused by the filtering of the output signal obtained from the main microphone. It is characterized by including a signal processing unit that generates a sound collecting signal in which the back and side sensitivities are suppressed by adding.

Further, the directional microphone of the sixth aspect according to the present invention is a directional microphone having anterior narrow directionalness in which the suppression amount of the back surface and side sensitivity can be adjusted, and the anterior narrow directionality is achieved by using an acoustic tube. A pair of main microphones to be held and arranged along the longitudinal direction of the acoustic tube and brought close to each other in the same direction and opposite directions to the front direction forming the front narrow directional main axis. Unidirectional microphones, omnidirectional omnidirectional microphones arranged between the pair of unidirectional microphones, and the anterior narrow directional microphones arranged along the longitudinal direction of the acoustic tube. For each output signal obtained from the unidirectional sub-microphone having a directing direction opposite to the front direction forming the main axis, the pair of unidirectional microphones, and the omnidirectional microphone. The filtered signal is added to generate a sideways cancel signal for suppressing the side sensitivity of the main microphone, in the front direction forming the front narrow directional main axis of the pair of unidirectional microphones. On the other hand, in order to suppress the back sensitivity of the main microphone by adding a filtered signal to each output signal obtained from the unidirectional microphone having the opposite direction and the sub microphone. A signal that generates a rearward canceling signal and adjusts the amplitude of the sideways canceling signal based on an external instruction, a signal that adjusts the amplitude of the rearward canceling signal based on an external instruction, and a signal from the main microphone. To the obtained output signal, a signal that has been delayed to compensate for the delay caused by the filter processing is added to generate a sound pickup signal in which the suppression amount of the back surface and side sensitivity can be adjusted individually. It is characterized by including a signal processing unit.

Further, the video camera with a variable directional microphone according to the present invention transmits a zoom control signal to the directional microphone according to the sixth aspect of the present invention, an optical lens with a zoom function, and the optical lens with a zoom function based on an external instruction. An image pickup control unit that outputs a zoom operation to determine the image angle and generates a signal of an image of the subject through the zoom operation, and a directivity when the image angle is narrow based on the zoom control signal. When the angle of view is wide, the suppression amount adjustment signal is output to the directional microphone to increase the suppression amount of the back and side sensitivity, and to decrease the suppression amount of the back and side sensitivity when the angle of view is wide. It is characterized by including a sound collection control unit that controls to generate a sound collection signal in which the suppression amount of the rear surface and side sensitivity is automatically adjusted according to the zoom control signal.

According to the present invention, it is possible to configure a directional microphone that suppresses sensitivity in a predetermined directional direction with high accuracy over a wide band, and a video camera with a variable directional microphone.

It is a figure which shows the schematic structure of the directional microphone (back sensitivity suppression type directional microphone) of 1st Embodiment by this invention. (A) to (k) are diagrams showing the simulation results of the sensitivity directional characteristics in the directional microphone of the first embodiment according to the present invention, respectively. It is a figure which shows the schematic structure of the directional microphone (back sensitivity suppression type directional microphone) of the 2nd Embodiment by this invention. (A) and (b) are diagrams showing the schematic configuration of the directional microphone (doughnut-shaped directional microphone) of the third embodiment according to the present invention and the directional characteristics of the directional microphone, respectively. It is a figure which shows the schematic structure of the directional microphone (side sensitivity suppression type directional microphone) of 4th Embodiment by this invention. It is a figure which shows the schematic structure of the directional microphone (backward and side sensitivity suppression type directional microphone) of the 5th Embodiment by this invention. It is a figure which shows the schematic structure of the directional microphone (the directional microphone of the back sensitivity and side sensitivity suppression amount adjustment type) of the 6th Embodiment by this invention. (A) to (k) are diagrams showing the simulation results of the sensitivity directional characteristics in the directional microphone according to the sixth embodiment of the present invention, respectively. It is a figure which shows the schematic structure of the video camera with the variable directional microphone of one Embodiment by this invention which makes it possible to change the directivity according to a zoom by using the directional microphone of 6th Embodiment by this invention. ..

Hereinafter, with reference to the drawings, the directional microphone according to the first to fifth embodiments according to the present invention and the variable directional microphone according to the present invention configured by using the directional microphone according to the fifth embodiment. The attached video camera will be described in order.

[First Embodiment] (Back-sensitivity suppression type directional microphone)
FIG. 1 is a diagram showing a schematic configuration of a directional microphone 10 according to a first embodiment of the present invention. The directional microphone 10 of the first embodiment is configured as a back-sensitivity suppression type directional microphone.

The directional microphone 10 shown in FIG. 1 includes a main microphone 12 having an anterior narrow directivity using an acoustic tube 11 and a first sub-microphone 13a having a rear unidirectionality arranged near the rear end of the acoustic tube 11. A second sub-microphone 13b having rear unidirectional directivity arranged near the tip of the acoustic tube 11 and a signal processing unit 14 are provided. The signal processing unit 14 includes a first filter 141, a second filter 142, a delay device 145, and an adder 146.

The main microphone 12 is generally called a microphone capsule, and by arranging it at the rear end of the acoustic tube 11, it can have forward narrow directivity (the front front is θ = 0 °), and the main microphone can be provided. The 12 and the acoustic tube 11 are also collectively referred to as a line microphone.

The acoustic tube 11 is formed in a cylindrical or square cylinder shape having a predetermined length for obtaining narrow angle directivity only at high frequencies, and has a plurality of openings 11a for phase interference on its side surface at regular intervals. ing. The main microphone 12 arranged at the rear end of the acoustic tube 11 has directivity in the rearward direction in the mid-low frequency band.

Therefore, in order to suppress the back sensitivity in a wide band over the entire audible frequency band without affecting the directional sensitivity characteristic of the main microphone 12, near the rear end of the acoustic tube 11 and near the tip of the acoustic tube 11. Is provided with a first sub-microphone 13a and a second sub-microphone 13b, which are generally referred to as microphone capsules.

The first sub-microphone 13a and the second sub-microphone 13b are rearward single facing 180 ° opposite to the directivity axis of the main microphone 12 (dashed arrow indicating the forward directivity direction) (dashed arrow indicating the backward directivity direction), respectively. Has unidirectionality.

The arrangement positions of the first sub-microphone 13a and the second sub-microphone 13b are not limited to the example of the present embodiment, and may be appropriately adjusted according to the processing of the signal processing unit 14 described later. Further, in the example of the present embodiment, an example in which two of the first and second sub-microphones 13a and 13b are used is shown, but the number may be one or three or more.

The output signal of the main microphone 12 is amplified by an amplifier and subjected to A / D conversion processing by an analog / digital (A / D) converter (the amplifier and the A / D converter are not shown). It is input to the delay device 145 in the signal processing unit 14. Similarly, the output signals of the first and second sub-microphones 13a and 13b are also amplified by an amplifier and subjected to A / D conversion processing by an A / D converter (amplifier and A / D conversion). (Not shown in the device), are input to the first filter 141 and the second filter 142 in the signal processing unit 14, respectively.

The first filter 141 performs a filter process for canceling the response in the back direction of the main microphone to the digital output signal obtained from the first sub microphone 13a, and outputs the digital output signal to the adder 146.

The second filter 142 applies a filter process to cancel the response in the back direction of the main microphone to the digital output signal obtained from the second sub microphone 13b, and outputs the digital output signal to the adder 146.

The delay device 145 performs delay processing on the digital output signal obtained from the main microphone 12 and outputs it to the adder 146 so as to compensate for the delay amount generated by the filter processing by the first filter 141 and the second filter 142, respectively. ..

The adder 146 inputs and adds the digital output signals of the main microphone 12, the first and second sub microphones 13a, 13b obtained through the delay device 145, the first filter 141, and the second filter 142, respectively. As a result, a sound pickup signal with suppressed back sensitivity is generated and output to the outside.

Here, the filter processing relating to the first filter 141 and the second filter 142 will be described in more detail.

Let m (θ, ω) be the transmission function when a sound wave having a frequency ω is incident on the main microphone 12 from the direction of the directing angle θ via the acoustic tube 11.

Further, each output signal of n (n ≧ 1) sub-microphones is g ₁ (θ, ω), g ₂ (θ, ω), ..., G _n (θ, ω), respectively, and n pieces in total. The output signal vector G (θ, ω) of the sub-microphone, and the output signal vector of the sub-microphone in the direction of the directing angle θ = 0 ° and the direction of θ = 180 ° are generally G (ω) = [G (0). , Ω), G (180, ω)] ^T. In the example of this embodiment, the first and second sub-microphones 13a and 13b with n = 2 can be generalized as n sub-microphones.

Further, let W (ω) = [w ₁ (ω), w ₂ (ω), ..., w _n (ω)] ^T be the transfer function vector of the filter that processes the digital output signal of each sub-microphone. Note that T represents a transposed matrix. In the example of this embodiment, the first filter 141 and the second filter 142 have n = 2, but they can be generalized as n filters.

First, the final output vector Y (ω) = [y (0, ω), y (180, ω)] ^T at an arbitrary frequency in the direction of the directivity angle θ = 0 ° and the direction of θ = 180 ° in the signal processing unit 14. Is the equation (1) by adding the output signal vector M (ω) after the delay processing of the main microphone 12 and the digital output signal vector G (ω) W (ω) after the filter processing of each sub microphone. Can be represented.

By the way, in order to suppress the back sensitivity over the entire audible band without affecting the sensitivity directional characteristic in the front direction of the main microphone 12, the direction of the directional angle θ = 0 ° and the direction of θ = 180 ° in the signal processing unit 14 The target characteristic vector D (ω) = [d (0, ω), d (180, ω)] ^T of the final output in the direction is expressed by the equation (2). Here, d (0, ω) and d (180, ω) are the target sensitivity-oriented characteristics in the front direction and the sensitivity-oriented characteristics in the back direction, respectively.

Therefore, as the sound pick-up signal output from the signal processing unit 14, the final output vector Y (ω) at an arbitrary frequency of θ = 0 ° and 180 ° and the target characteristic vector D (ω) of θ = 0 ° and 180 °. To minimize the squared error of, as the transfer function vector W (ω) of the filter that processes the digital output signal of each sub-microphone.
W (ω) = (G (ω) ^HG (ω)) ^-1 G (ω) ^H (D (ω) -M (ω))
A digital filter processing having a transfer function is performed. Here, H represents the Hermitian transpose matrix.

Here, another example of filter design will be described.

Let m (θ, ω) be the transmission function when a sound wave having a frequency ω is incident on the main microphone 12 from the direction of the directing angle θ via the acoustic tube 11.

Further, each output signal of n (n ≧ 1) sub-microphones is g ₁ (θ, ω), g ₂ (θ, ω), ..., G _n (θ, ω), respectively, and n pieces in total. The output signal vector G (θ, ω) of the sub-microphone, and the output signal vector of the sub-microphone in the directions of the directing angles θ = 0 °, θ ₁ , θ ₂ , ..., 180 ° are generally G (ω) =. [G (0, ω), G (θ ₁ , ω), G (θ ₂ , ω), ..., G (180, ω)] ^T. In the example of this embodiment, the first and second sub-microphones 13a and 13b with n = 2 can be generalized as n sub-microphones.

Further, let W (ω) = [w ₁ (ω), w ₂ (ω), ..., w _n (ω)] ^T be the transfer function vector of the filter that processes the digital output signal of each sub-microphone. Note that T represents a transposed matrix. In the example of this embodiment, the first filter 141 and the second filter 142 have n = 2, but they can be generalized as n filters.

First, the final output vectors Y (ω) = [y (0, ω), y (θ ₁ ) at arbitrary frequencies in the directions of the directing angles θ = 0 °, θ ₁ , θ ₂ , ..., 180 ° in the signal processing unit 14. , Ω), y (θ ₂ , ω), ..., y (180, ω)] ^T is the output signal vector M (ω) after the delay processing of the main microphone 12 and the digital after the filtering processing of each sub microphone. It can be expressed by the equation (3) by adding the output signal vectors G (ω) W (ω).

By the way, in order to suppress the back sensitivity over the entire audible band without affecting the sensitivity directional characteristic of the main microphone 12 in a specific direction, the directional angles θ = 0 °, θ ₁ , θ ₂ in the signal processing unit 14. …, Target characteristic vector D (ω) = [d (0, ω), d (θ ₁ , ω), d (θ ₂ , ω),…, d (180, ω) of the final output in the direction of 180 ° ] ^{Let T} be the equation (4). Here, d (0, ω), d (θ ₁ , ω), d (θ ₂ , ω), ..., D (180, ω) are θ = 0 °, θ ₁ , θ ₂ , respectively. It is a sensitivity-directed characteristic targeted at a direction of 180 °, and h (θ, ω) represents the weight of the target suppression amount for each direction. h (θ, ω) takes a value in the range of 0 ≦ h (θ, ω) ≦ 1, and the closer the value of h (θ, ω) is to 0, the larger the target suppression amount.

For the purpose of suppressing the sensitivity in a direction other than the front while maintaining the sensitivity in the front direction, for example, as an example of h (θ, ω), the following can be given.
h (θ, ω) = 0.5 (1-cos (θ))

Therefore, as the sound pick-up signal output from the signal processing unit 14, the final output vector Y (ω) at an arbitrary frequency of θ = 0 °, θ ₁ , θ ₂ , ..., 180 ° and θ = 0 °, θ ₁ , Θ ₂ , ..., To minimize the squared error of the target characteristic vector D (ω) at 180 °, use the transfer function vector W (ω) of the filter that processes the digital output signal of each sub-microphone.
W (ω) = (G (ω) ^HG (ω)) ^-1 G (ω) ^H (D (ω) -M (ω))
A digital filter processing having a transfer function is performed. Here, H represents the Hermitian transpose matrix.

When the filter is designed using this method, the sensitivity directional characteristic can be suppressed not only in the direction of θ = 180 ° but also in the direction having a certain width. However, as described above, when only the front direction θ = 0 ° and the back direction θ = 180 ° are specified, the suppression amount of the sensitivity in the θ = 180 ° direction is improved and in the low frequency band. Tends to have a high suppression effect even in a certain angle range.

When a 70 cm long acoustic tube is used in FIGS. 2 (a) and 2 (k) and three sub-microphones are used, the directivity direction (front front direction) of the main microphone 12 is set to θ = 0 ° and 0. The simulation result of the sensitivity directivity with respect to ° ≤ θ ≤ 360 ° (that is, 0 ° ≤ | θ | ≤ 180 °) is shown. In FIGS. 2 (a) and 2 (k), the characteristic of D1 shown is a sensitivity-oriented characteristic when the back surface suppression process is not applied, and the characteristic of D2 shown is the case where the back surface sensitivity suppression process is applied. This is the sensitivity-oriented characteristic of. Although the range differs depending on the frequency, it can be seen that the sensitivity is suppressed at θ = 60 ° to 300 °.

Therefore, in the example shown in FIG. 1, the signal processing unit 14 described above with respect to the digital output signals obtained from the first and second sub microphones 13a and 13b by the first filter 141 and the second filter 142 where n = 2. The digital output signal obtained from the main microphone 12 is subjected to the delay processing according to the equation (1) by the delay device 145, and added by the adder 146. Thereby, it is possible to generate a sound pickup signal in which the back sensitivity is suppressed with high accuracy over the entire audible frequency band without affecting the sensitivity directional characteristic in the front direction of the main microphone 12. The filter design method does not matter as long as the difference between Y (ω) and D (ω) is minimized according to a predetermined norm.

In this way, the directional microphone 10 of the first embodiment can be configured as a directional microphone having a narrow directivity in the front direction in which the sensitivity in the back direction is suppressed in a wide band and with high accuracy.

[Second Embodiment] (Another example of a back-sensitivity suppression type directional microphone)
FIG. 3 is a diagram showing a schematic configuration of the directional microphone 20 according to the second embodiment of the present invention. The directional microphone 20 of the second embodiment is similar to the first embodiment in that it is configured as a directional microphone of the back sensitivity suppression type, but the delay device 145 is used in the signal processing unit 14 shown in FIG. The difference is that the third filter 245, which performs digital filter processing, is used instead.

The directional microphone 20 shown in FIG. 3 includes a main microphone 22 having an anterior narrow directivity using an acoustic tube 21, and a first sub-microphone 23a having a rear unidirectionality arranged near the rear end of the acoustic tube 21. A second sub-microphone 23b having rear unidirectional directivity arranged near the tip of the acoustic tube 21 and a signal processing unit 24 are provided. The signal processing unit 24 includes a first filter 241, a second filter 242, a third filter 245, and an adder 246.

The line microphone composed of the main microphone 22 and the acoustic tube 21 in the second embodiment may be the same as the line microphone composed of the main microphone 12 and the acoustic tube 11 in the first embodiment. can. Therefore, the acoustic tube 21 is configured in the shape of a cylinder or a square cylinder having a predetermined length for obtaining narrow angle directivity only at high frequencies, and has a plurality of openings 21a for phase interference on its side surface at regular intervals. ing.

Further, also in the present embodiment, in order to suppress the back sensitivity over the entire audible frequency band without affecting the sensitivity directivity in the front direction of the main microphone 22, the vicinity of the rear end of the acoustic tube 21 and the acoustic tube 21 A first sub-microphone 23a and a second sub-microphone 23b, which are generally called a microphone capsule, are provided in the vicinity of the tip of the microphone.

The first sub-microphone 23a and the second sub-microphone 23b are rearward single facing 180 ° opposite to the directivity axis of the main microphone 22 (dashed arrow indicating the forward directivity direction) (dashed arrow indicating the backward directivity direction), respectively. Has unidirectionality.

Also in this embodiment, the arrangement positions of the first sub-microphone 23a and the second sub-microphone 23b are not limited to the illustrated examples, and may be appropriately adjusted according to the processing of the signal processing unit 24 described later. .. Further, in the example of the present embodiment, an example in which two of the first and second sub-microphones 23a and 23b are used is shown, but the number may be one or three or more.

The output signal of the main microphone 22 is amplified by an amplifier and subjected to A / D conversion processing by an analog / digital (A / D) converter (the amplifier and the A / D converter are not shown). It is input to the third filter 245 in the signal processing unit 24. Similarly, the output signals of the first and second sub-microphones 23a and 23b are also amplified by an amplifier and subjected to A / D conversion processing by an A / D converter (amplifier and A / D conversion). (Not shown in the device), are input to the first filter 241 and the second filter 242 in the signal processing unit 24, respectively.

The first filter 241 applies a filter process to cancel the response in the back direction of the main microphone to the digital output signal obtained from the first sub microphone 23a, and outputs the digital output signal to the adder 246.

The second filter 242 applies a filter process to cancel the response in the back direction of the main microphone to the digital output signal obtained from the second sub microphone 23b, and outputs the digital output signal to the adder 246.

The digital output signal obtained from the main microphone 22 is subjected to a filter process for compensating for the frequency characteristic in the front direction, and is output to the adder 246.

The adder 246 inputs and adds the digital output signals of the main microphone 22, the first and second sub microphones 23a, 23b obtained through the third filter 245, the first filter 241 and the second filter 242, respectively. As a result, a sound pickup signal with suppressed back sensitivity is generated and output to the outside.

Here, the filter processing relating to the first filter 241 and the second filter 242, and the third filter 245 will be described in more detail.

Let m (θ, ω) be the transmission function when a sound wave having a frequency ω is incident on the main microphone 22 from the direction of the directing angle θ via the acoustic tube 21.

Further, each output signal of n (n ≧ 1) sub-microphones is g ₁ (θ, ω), g ₂ (θ, ω), ..., G _n (θ, ω), respectively, and this embodiment. Then, the output signal of the transmission function m (θ, ω) of the main microphone and each output signal of the n sub-microphones are generally set as the output signal vector G (θ, ω), and the directing angle θ = 0 °. The output signal vectors in the direction of and the direction of θ = 180 ° are generally G (ω) = [G (0, ω), G (180, ω)] ^T. In the example of this embodiment, the first and second sub-microphones 23a and 23b with n = 2 can be generalized as n sub-microphones.

Further, the transfer function of the filter that processes the digital output signals of the main microphone 22 and each sub microphone is W (ω) = [w ₁ (ω), w ₂ (ω), ..., w _{n + 1} (ω)] ^T. And. Note that T represents a transposed matrix. In the example of the present embodiment, the third filter 245 for one main microphone 22 and the first filter 241 and the second filter 242 with n = 2 can be generalized as n + 1 filters.

First, the final output vector Y (ω) = [y (0, ω), y (180, ω)] ^T at an arbitrary frequency in the direction of the directivity angle θ = 0 ° and the direction of θ = 180 ° in the signal processing unit 24. Can be expressed by the equation (5) as a vector G (ω) W (ω) obtained by vector-adding the filtered digital output signals of the main microphone 22 and each sub microphone.

By the way, in order to suppress the back sensitivity over the entire audible frequency band without affecting the sensitivity directional characteristic in the front direction of the main microphone 22, the direction of the directional angle θ = 0 ° and θ = 180 ° in the signal processing unit 24. The target characteristic vector D (ω) = [d (0, ω), d (180, ω)] ^T of the final output in the direction of is expressed by the equation (6). Here, d (0, ω) and d (180, ω) are the target sensitivity-oriented characteristics in the front direction and the sensitivity-oriented characteristics in the back direction, respectively.

Therefore, as the sound pick-up signal output from the signal processing unit 24, the final output vector Y (ω) at an arbitrary frequency of θ = 0 ° and 180 ° and the target characteristic vector D (ω) of θ = 0 ° and 180 °. To minimize the squared error of, the transfer function vector W (ω) of the filter that processes the digital output signals of the primary microphone 22 and each sub microphone is used.
W (ω) = (G (ω) ^HG (ω)) ^-1 G (ω) ^HD (ω)
A digital filter processing having a transfer function is performed. Here, H represents the Hermitian transpose matrix.

Here, another example of filter design will be described.

Let m (θ, ω) be the transmission function when a sound wave having a frequency ω is incident on the main microphone 22 from the direction of the directing angle θ via the acoustic tube 21.

Further, each output signal of n (n ≧ 1) sub-microphones is g ₁ (θ, ω), g ₂ (θ, ω), ..., G _n (θ, ω), respectively, and n pieces in total. The output signal vector G (θ, ω) of the sub-microphone, and the output signal vector of the sub-microphone in the directions of the directing angles θ = 0 °, θ ₁ , θ ₂ , ..., 180 ° are generally G (ω) =. [G (0, ω), G (θ ₁ , ω), G (θ ₂ , ω), ..., G (180, ω)] ^T. In the example of this embodiment, the first and second sub-microphones 23a and 23b with n = 2 can be generalized as n sub-microphones.

Further, the transfer function of the filter that processes the digital output signals of the main microphone 22 and each sub microphone is W (ω) = [w ₁ (ω), w ₂ (ω), ..., w _{n + 1} (ω)] ^T. And. Note that T represents a transposed matrix. In the example of the present embodiment, the third filter 245 for one main microphone 22 and the first filter 241 and the second filter 242 with n = 2 can be generalized as n + 1 filters.

First, the final output vector Y (ω) = [y (0, ω), y (θ ₁ ) at an arbitrary frequency in the direction of the directivity angles θ = 0 °, θ ₁ , θ ₂ , ..., 180 ° in the signal processing unit 14. , Ω), y (θ ₂ , ω), ..., y (180, ω)] ^T is the output signal vector M (ω) after filtering of the main microphone 22 and the digital after filtering of each sub-microphone. It can be expressed by the equation (7) by adding the output signal vectors G (ω) W (ω).

By the way, in order to suppress the back sensitivity over the entire audible band without affecting the sensitivity directional characteristic of the main microphone 22 in a specific direction, the directional angles θ = 0 °, θ ₁ , θ ₂ in the signal processing unit 24, …, Target characteristic vector D (ω) = [d (0, ω), d (θ ₁ , ω), d (θ ₂ , ω),…, d (180, ω) of the final output in the direction of 180 ° ] ^{Let T} be the equation (8). Here, d (0, ω), d (θ ₁ , ω), d (θ ₂ , ω), ..., D (180, ω) are θ = 0 °, θ ₁ , θ ₂ , respectively. It is a sensitivity-directed characteristic targeted at a direction of 180 °, and h (θ, ω) represents the weight of the target suppression amount for each direction. h (θ, ω) takes a value in the range of 0 ≦ h (θ, ω) ≦ 1, and the closer the value of h (θ, ω) is to 0, the larger the target suppression amount.

For the purpose of suppressing the sensitivity in a direction other than the front while maintaining the sensitivity in the front direction, for example, as an example of h (θ, ω), the following can be given.
h (θ, ω) = 0.5 (1-cos (θ))

Therefore, as the sound pick-up signal output from the signal processing unit 24, the final output vector Y (ω) at an arbitrary frequency of θ = 0 °, θ ₁ , θ ₂ , ..., 180 ° and θ = 0 °, θ ₁ , Θ ₂ , ..., To minimize the squared error of the target characteristic vector D (ω) in the direction of 180 °, the transfer function vector W of the filter that processes the digital output signals of the primary microphone 22 and each sub-microphone ( As ω),
W (ω) = (G (ω) ^HG (ω)) ^-1 G (ω) ^HD (ω)
A digital filter processing having a transfer function is performed. Here, H represents the Hermitian transpose matrix.

When the filter is designed using this method, the sensitivity directional characteristic can be suppressed not only in the direction of θ = 180 ° but also in the direction having a certain width. However, as described above, when only the front direction θ = 0 ° and the back direction θ = 180 ° are specified, the suppression amount of the sensitivity in the θ = 180 ° direction is improved and in the low frequency band. Tends to have a high suppression effect even in a certain angle range.

Therefore, in the example shown in FIG. 3, the signal processing unit 24 uses the third filter 245 and the first filter 241 and the second filter 242 in which n = 2, so that the main microphone 22 and the first and second sub microphones 23a, The digital output signals obtained from 23b are subjected to the above-mentioned digital filter processing having a transmission function of W (ω), and the addition is performed by the adder 246, which affects the sensitivity directional characteristics in the front direction of the main microphone 22. It is possible to generate a sound pickup signal in which the back sensitivity is suppressed with high accuracy over the audible frequency band without giving. The filter design method does not matter as long as the difference between Y (ω) and D (ω) is minimized according to a predetermined norm.

In this way, the directional microphone 20 of the second embodiment can be configured as a directional microphone having a narrow directivity in the front direction in which the sensitivity in the back direction is suppressed in a wide band and with high accuracy.

[Third Embodiment] (Donut-shaped directional microphone)
4 (a) and 4 (b) are diagrams showing the schematic configuration of the directional microphone 30 according to the third embodiment of the present invention and the directional characteristics of the directional microphone, respectively. The directional microphone 30 of the third embodiment is configured as a donut-shaped directional microphone.

The directional microphone 30 shown in FIG. 4A is a pair of unidirectional microphones (a first microphone 33a having a rear unidirectional characteristic and a front unidirectional characteristic) that are brought close to each other with their opposite directivity directions facing each other. The third microphone 33c), the second microphone 33b having omnidirectionality arranged between the first microphone 33a and the third microphone 33c, and the signal processing unit 34 are provided. The signal processing unit 34 includes a first filter 341, a second filter 342, a third filter 343, and an adder 346. The first to third microphones 33a to 33c are generally referred to as microphone capsules.

The signal processing unit 34 performs low-pass filter processing for band-limiting each output signal of the first to third microphones 33a to 33c by the first filter 341, the second filter 342, and the third filter 343, and by the adder 346. It is configured to perform addition processing.

First, the sensitivity directional characteristic D _cardioid (θ) of the pair of unidirectional microphones (the first microphone 33a having the rear unidirectional characteristic and the third microphone 33c having the anterior unidirectional characteristic) is the front front θ =. Assuming 0 °, the linear sum of omnidirectional and bidirectional
D _cardioid (θ) = a · (1 + cosθ)
Can be represented by. Here, the constant a indicates the sensitivity in the front direction.

Further, since the second microphone 33b having omnidirectionality has a constant sensitivity directivity characteristic _Domni (θ) regardless of the direction,
_Domni (θ) = a
Can be represented by a constant a.

Therefore, in the signal processing unit 34 shown in FIG. 4A, a low-pass filter process for band-limiting each output signal of the first to third microphones 33a to 33c by each of the first to third filters 341 to 343 is performed. And output to the adder 346.

The adder 346 includes each output signal of the pair of unidirectional microphones (first and third microphones 33a, 33c) after the low-pass filter processing, and the omnidirectional microphone (second microphone 33b) of the low-pass filter processing. The difference from the later output signal is once calculated to obtain a signal with anti-phase bidirectionality, and the output signal of the pair of unidirectional microphones after the low-pass filter processing is added to this signal. Then, the sensitivity directivity characteristic D _cos2 (θ) = a · cos ² (θ) having bidirectionality on the side is obtained, and further, this sensitivity directivity characteristic D _cos2 (θ) is used as an omnidirectional microphone (No. 1). 2 Sensitivity directivity characteristic D _sin2 (θ) = which has a donut-shaped directivity perpendicular to the directivity axis of a pair of unidirectional microphones, which is different from the output signal of the microphone 33b) after the low-pass filter processing. An output signal of a · cos ² (θ) = a · sin ² (θ) is generated, and this is output to the outside as a sound pickup signal.

As a result, as shown in FIG. 4B, when the X-axis is the front front θ = 0 °, a donut-shaped directional microphone with suppressed sensitivity in the Z-axis direction can be configured. In this example, the adder 346 with the low-pass filter processing has been described, but as will be clarified in the fourth embodiment described later, the filter processing for compensating the frequency characteristics in the front direction, the side direction, and the back direction is included. It can also be configured as an adder.

In this way, the directional microphone 30 of the third embodiment can be configured as a donut-shaped directional microphone, for example, on a table surrounded by a plurality of people, at the height of the mouths of the plurality of people. When the directional microphone 30 of the embodiment is placed, while collecting the sounds of the plurality of persons, other extra sounds (for example, the rubbing sound of the document generated when the plurality of persons handle the document, the chair, etc.) are placed. (Rubbing noise or mechanical noise such as air conditioning) is suppressed, and a clear sound pickup signal can be obtained for the voices of the plurality of people.

[Fourth Embodiment] (Side-sensitivity suppression type directional microphone)
FIG. 5 is a diagram showing a schematic configuration of the directional microphone 40 according to the fourth embodiment of the present invention. The directional microphone 40 of the fourth embodiment is configured as a side sensitivity suppressing type directional microphone.

The directional microphone 40 shown in FIG. 5 is a pair of a main microphone 42 having a forward narrow directivity using an acoustic tube 41 and a pair arranged in the vicinity of the rear end of the acoustic tube 41 and brought close to each other in opposite directivity directions. Between the unidirectional sub-microphone (the first sub-microphone 43a having the rear unidirectional characteristic and the third sub-microphone 43c having the anterior unidirectional characteristic) and the first sub-microphone 43a and the third sub-microphone 43c. It includes a second sub-microphone 43b having omnidirectional arrangement and a signal processing unit 44. The signal processing unit 44 includes a first filter 441, a second filter 442, a third filter 443, a delay device 445, and an adder 446.

Here, the first to third sub-microphones 43a to 43c in the directional microphone 40 of the fourth embodiment are configured in the same manner as the first to third microphones 33a to 33c in the directional microphone 30 of the third embodiment, respectively. To.

Further, the line microphone in which the main microphone 42 and the acoustic tube 41 in the directional microphone 40 of the fourth embodiment are combined is a line in which the main microphone 12 and the acoustic tube 11 in the first embodiment are combined. It can be similar to a microphone. Therefore, the acoustic tube 41 is configured in the shape of a cylinder or a square cylinder having a predetermined length for obtaining narrow angle directivity only at high frequencies, and has a plurality of openings 41a for phase interference at regular intervals on its side surface. ing.

The directional microphone 40 of the fourth embodiment is a line microphone composed of a main microphone 42 and an acoustic tube 41, and a donut-shaped directivity described in the third embodiment in order to suppress lateral sensitivity. By combining with a microphone, it is configured as a narrow directivity microphone having a narrow directivity in the front direction of a side sensitivity suppression type.

The output signal of the main microphone 42 is amplified by an amplifier and subjected to A / D conversion processing by an analog / digital (A / D) converter (the amplifier and the A / D converter are not shown). It is input to the delay device 445 in the signal processing unit 44. Similarly, each output signal of the first to third sub microphones 43a to 43c is also amplified by an amplifier and subjected to A / D conversion processing by an A / D converter (amplifier and A / D conversion). (Not shown in the device) are input to the first to third filters 441 to 443 in the signal processing unit 44, respectively.

The first filter 441 applies a filter process to cancel the response in the lateral direction of the main microphone to the digital output signal obtained from the first sub microphone 43a, and outputs the digital output signal to the adder 446.

The second filter 442 applies a filter process to cancel the response in the lateral direction of the main microphone to the digital output signal obtained from the second sub microphone 43b, and outputs the digital output signal to the adder 446.

The third filter 443 performs a filter process for canceling the response in the lateral direction of the main microphone to the digital output signal obtained from the third sub microphone 43c, and outputs the digital output signal to the adder 446.

The delay device 445 performs delay processing on the digital output signal obtained from the main microphone 42 so as to compensate for the delay amount generated by the filter processing by the first to third filters 441 to 443, and outputs the delay process to the adder 446. ..

The adder 446 inputs and adds the digital output signals of the main microphone 42 and the first to third sub microphones 43a to 43c obtained through the delay device 445 and the first to third filters 441 to 443, respectively. , Generates a sound pickup signal with suppressed side sensitivity and outputs it to the outside.

Here, the filter processing relating to the first to third filters 441 to 443 will be described in more detail.

Let m (θ, ω) be the transmission function when a sound wave having a frequency ω is incident on the main microphone 42 from the direction of the directing angle θ via the acoustic tube 41.

Further, the transmission functions when a sound wave having a frequency ω is incident on the first to third sub-microphones 43a to 43c from the direction of the directing angle θ are g _side1 (θ, ω), g _side2 (θ, ω), respectively. g _side3 (θ, ω), the output signal vector G _side (ω) of the sub-microphone, and the output signal in the direction of the directing angle θ = 0 °, the direction of θ = 90 °, and the direction of θ = 180 °. Let the vector as a whole be G _side (ω) = [G _side (0, ω), G _side (90, ω), G _side (180, ω)] ^T.

Further, the transfer function of the filter that processes the digital output signal of each sub-microphone is W _side (ω) = [w _side1 (ω), w _side2 (ω), w _side3 (ω)] ^T. Note that T represents a transposed matrix.

First, the final output vector Y (ω) = [y (0, ω), y at an arbitrary frequency in the direction of the directivity angle θ = 0 °, the direction of θ = 90 °, and the direction of θ = 180 ° in the signal processing unit 44. (90, ω), y (180, ω)] ^T is the output signal vector M _side (ω) after the delay processing of the main microphone 42 and the digital output signal vector G _side (ω) after the filtering processing of each sub microphone. ) W _side (ω) can be added by a vector and expressed by the equation (9).

By the way, in order to suppress the lateral sensitivity over the entire audible frequency band without affecting the sensitivity directional characteristic in the front direction of the main microphone 42, the direction of the directional angle θ = 0 ° and θ = 90 ° in the signal processing unit 44. The target characteristic vector D _side (ω) = [d (0, ω), d (90, ω), d (180, ω)] ^T of the final output in the direction of and the direction of θ = 180 °. ). Here, d (0, ω), d (90, ω), and d (180, ω) are the target front-direction sensitivity directional characteristics, side-side sensitivity directional characteristics, and back-side sensitivity directional characteristics, respectively. be.

Therefore, as the sound pick-up signal output from the signal processing unit 44, the final output vector Y (ω) at an arbitrary frequency of θ = 0 °, 90 °, 180 ° and the target of θ = 0 °, 90 °, 180 °. To minimize the squared error of the characteristic vector D _side (ω), use the transfer function vector W (ω) of the filter that processes the digital output signal of each sub-microphone.
W _side (ω) = (G _side (ω) ^HG _side (ω)) ^-1 G _side (ω) ^H (D _side (ω) -M _side (ω))
A digital filter processing having a transfer function is performed. Here, H represents the Hermitian transpose matrix.

Here, another example of filter design will be described.

Let m (θ, ω) be the transmission function when a sound wave having a frequency ω is incident on the main microphone 42 from the direction of the directing angle θ via the acoustic tube 41.

Further, the transmission functions when a sound wave having a frequency ω is incident on the first to third sub-microphones 43a to 43c from the direction of the directing angle θ are g _side1 (θ, ω), g _side2 (θ, ω), respectively. g _side3 (θ, ω), the output signal vector of the sub-microphone G _side (ω), and the output signal of the sub-microphone in the direction of the directing angles θ = 0 °, θ ₁ , θ ₂ , ..., 180 °. The vectors are generally G _side (ω) = [G _side (0, ω), G _side (θ ₁ , ω), G _side (θ ₂ , ω), ..., G _side (180, ω)] ^T.

Further, the transfer function vector of the filter that processes the digital output signal of each sub-microphone is W _side (ω) = [w _side1 (ω), w _side2 (ω), w _side3 (ω)] ^T. Note that T represents a transposed matrix.

First, the final output vector Y (ω) = [y (0, ω), y (θ ₁ ) at an arbitrary frequency in the direction of the directing angles θ = 0 °, θ ₁ , θ ₂ , ..., 180 ° in the signal processing unit 44. , Ω), y (θ ₂ , ω), ..., y (180, ω)] ^T is the output signal vector M (ω) after the delay processing of the main microphone 42 and the digital after the filtering processing of each sub microphone. It can be expressed by the equation (11) by adding the output signal vectors G (ω) W (ω).

By the way, in order to suppress the lateral sensitivity over the entire audible frequency band without affecting the sensitivity directional characteristic in the front direction of the main microphone 42, the directional angles θ = 0 °, θ ₁ , θ ₂ in the signal processing unit 44, …, Target characteristic vector D (ω) = [d (0, ω), d (θ ₁ , ω), d (θ ₂ , ω),…, d (180, ω) of the final output in the direction of 180 ° ] ^{Let T} be the equation (12). Here, d (0, ω), d (θ ₁ , ω), d (θ ₂ , ω), ..., D (180, ω) are θ = 0 °, θ ₁ , θ ₂ , respectively. It is a sensitivity-directed characteristic targeted at a direction of 180 °, and h (θ, ω) represents the weight of the target suppression amount for each direction. h (θ, ω) takes a value in the range of 0 ≦ h (θ, ω) ≦ 1, and the closer the value of h (θ, ω) is to 0, the larger the target suppression amount.

For the purpose of suppressing the sensitivity in the lateral direction while maintaining the sensitivity in the front direction, the following can be given as an example of h (θ, ω), for example.
h (θ, ω) = sin ² (θ) | m (90, ω) | / | m (θ, ω) |

Therefore, as the sound pick-up signal output from the signal processing unit 44, the final output vector Y (ω) at an arbitrary frequency of θ = 0 °, θ ₁ , θ ₂ , ..., 180 ° and θ = 0 °, θ ₁ , Θ ₂ , ..., To minimize the squared error of the 180 ° target characteristic vector D _side (ω), use the transfer function vector W (ω) of the filter that processes the digital output signal of each sub-microphone.
W _side (ω) = (G _side (ω) ^HG _side (ω)) ^-1 G _side (ω) ^H (D _side (ω) -M _side (ω))
A digital filter processing having a transfer function is performed. Here, H represents the Hermitian transpose matrix.

When the filter is designed using this method, the sensitivity directional characteristic can be suppressed not only in the direction of θ = 90 ° but also in the direction having a certain width. However, as described above, when only the front direction θ = 0 °, the side direction θ = 90 °, and the back direction θ = 180 ° are specified, the suppression amount of the sensitivity in the θ = 90 ° direction tends to be improved. It is in.

Therefore, in the example shown in FIG. 5, the signal processing unit 44 receives the above-mentioned W _side (for the digital output signals obtained from the first to third sub-microphones 43a to 43c by the first to third filters 441 to 443, respectively. A digital filter process having a transmission function of ω) is applied, a delay process according to equation (5) is applied to the digital output signal obtained from the main microphone 42 by the delay device 445, and the signal is added by the adder 446. It is possible to generate a sound pickup signal in which the lateral sensitivity is suppressed with high accuracy over the entire audible frequency band without affecting the sensitivity directional characteristics in the front direction and the back direction of the microphone 42. The filter design method does not matter as long as the difference between Y (ω) and D (ω) is minimized according to a predetermined norm.

In this way, the directional microphone 40 of the fourth embodiment can be configured as a directional microphone having a narrow directivity in the front direction in which the sensitivity in the lateral direction is suppressed in a wide band and with high accuracy.

[Fifth Embodiment] (Back and side sensitivity suppression type directional microphone)
FIG. 6 is a diagram showing a schematic configuration of the directional microphone 50 according to the fifth embodiment of the present invention. The directional microphone 50 of the fifth embodiment is configured as a back and side sensitivity suppression type directional microphone.

The directional microphone 50 shown in FIG. 6 is a pair of a main microphone 52 having a forward narrow directivity using an acoustic tube 51 and a pair arranged in the vicinity of the rear end of the acoustic tube 51 and brought close to each other in opposite directivity directions. Between the unidirectional sub-microphone (the first sub-microphone 53a having the rear unidirectional characteristic and the third sub-microphone 53c having the anterior unidirectional characteristic) and the first sub-microphone 53a and the third sub-microphone 53c. It includes an omnidirectional second sub-microphone 53b arranged, a fourth sub-microphone 53d having a rear unidirectional characteristic arranged near the tip of the acoustic tube 51, and a signal processing unit 54. The signal processing unit 54 includes a first filter 541, a second filter 542, a third filter 543, a fourth filter 544, a delay device 545, and an adder 546. However, since the first sub-microphone 53a in the present embodiment has the rear unidirectional characteristic, it acts not only for suppressing the back sensitivity but also for suppressing the side sensitivity.

Here, the first to third sub-microphones 53a to 53c in the directional microphone 50 of the fifth embodiment are configured in the same manner as the first to third microphones 33a to 33c of the directional microphone 30 of the third embodiment, respectively. To.

Further, the fourth sub-microphone 53d in the directional microphone 50 of the fifth embodiment is configured in the same manner as the second sub-microphone 13b in the directional microphone 10 of the first embodiment.

Further, the line microphone in which the main microphone 52 and the acoustic tube 51 in the directional microphone 50 of the fifth embodiment are combined is a line in which the main microphone 12 and the acoustic tube 11 in the first embodiment are combined. It can be similar to a microphone. Therefore, the acoustic tube 51 is formed in the shape of a cylinder or a square cylinder having a predetermined length for obtaining narrow angle directivity only at high frequencies, and has a plurality of openings 51a for phase interference on its side surface at regular intervals. ing.

That is, the directional microphone 50 of the fifth embodiment combines the back sensitivity suppression processing of the first embodiment and the side sensitivity suppression processing of the fourth embodiment as the processing of the signal processing unit 54, so that the back and side sensitivities are sensitivity. It is configured as a repressive type narrow directional microphone with narrow directivity in the front direction.

The output signal of the main microphone 52 is amplified by an amplifier and subjected to A / D conversion processing by an analog / digital (A / D) converter (the amplifier and the A / D converter are not shown). It is input to the delay device 545 in the signal processing unit 54. Similarly, each output signal of the first to fourth sub microphones 53a to 53d is also amplified by an amplifier and subjected to A / D conversion processing by an A / D converter (amplifier and A / D conversion). (Not shown in the device) are input to the first to fourth filters 541 to 544 in the signal processing unit 54, respectively.

The first filter 541 performs a filter process on the digital output signal obtained from the first sub-microphone 53a by a transfer function having a directivity angle and a frequency as elements to cancel the response in the back and side directions of the main microphone. , Output to the adder 546.

The second filter 542 performs a filter process for canceling the lateral response of the main microphone to the digital output signal obtained from the second sub microphone 53b, and outputs the digital output signal to the adder 546.

The third filter 543 performs a filter process for canceling the response in the back and side directions of the main microphone to the digital output signal obtained from the third sub microphone 53c, and outputs the digital output signal to the adder 546.

The fourth filter 544 performs a filter process for canceling the response in the back direction of the main microphone to the digital output signal obtained from the fourth sub microphone 53d, and outputs the digital output signal to the adder 546.

The delay device 545 performs delay processing on the digital output signal obtained from the main microphone 52 so as to compensate for the delay amount generated by the filter processing by the first to fourth filters 541 to 544, and outputs the delay process to the adder 546. ..

The adder 546 inputs and adds the digital output signals of the main microphone 52 and the first to fourth sub microphones 53a to 53d obtained through the delay device 545 and the first to fourth filters 541 to 544, respectively. , Back and side side Sensitivity is suppressed and a sound pickup signal is generated and output to the outside.

Here, as the filter processing relating to the first to fourth filters 541 to 544, the design methods of the back sensitivity suppression filter processing in the first embodiment and the side sensitivity suppression filter processing in the fourth embodiment are used as they are. be able to.

However, since the first sub-microphone 53a in the present embodiment has a rear unidirectional characteristic, it acts not only for suppressing the back sensitivity but also for suppressing the side sensitivity. Therefore, the first filter 541 is the first filter. The filter is a linear sum of the filter process for suppressing back sensitivity in the embodiment and the filter process for suppressing side sensitivity in the fourth embodiment.

Therefore, in the example shown in FIG. 6, the signal processing unit 54 performs digital filter processing on the digital output signals obtained from the first to fourth sub-microphones 53a to 53d by the first to fourth filters 541 to 544, respectively. The signal for suppressing the rear and side sensitivity is generated, the digital output signal obtained from the main microphone 52 is delayed by the delay device 545, and the signal is added by the adder 546 to the front direction of the main microphone 52. It is possible to generate a sound pickup signal in which the rear and side sensitivity is suppressed with high accuracy in a wide frequency band (that is, an audible frequency band) extending from a low frequency band to a high frequency band without affecting the sensitivity directional characteristic.

In this way, the directional microphone 50 of the fifth embodiment can be configured as a directional microphone having narrow directivity in the front direction in which the sensitivity in the back surface and side directions is suppressed with high accuracy in a wide band.

[Sixth Embodiment] (Directivity microphone with rear sensitivity and side sensitivity suppression amount adjustment type)
FIG. 7 is a diagram showing a schematic configuration of the directional microphone 60 according to the sixth embodiment of the present invention. The directional microphone 60 of the sixth embodiment is configured as a directional microphone in which the back sensitivity and the side sensitivity are suppressed.

In the fifth embodiment described above, a filter having a linear sum of the one designed as the filter process for suppressing the back sensitivity in the first embodiment and the one designed as the filter process for suppressing the side sensitivity in the fourth embodiment is used. Although an example has been described, in the sixth embodiment, the output of the filter processing for suppressing the back sensitivity and the output of the filter processing for suppressing the side sensitivity are each variable in the amount of attenuation, instead of the linear sum. The directional microphone 60 of the sixth embodiment is made variable by providing the devices 648a and 648b so that the back sensitivity suppression amount and the side sensitivity suppression amount can be adjusted by the user.

The directional microphone 60 shown in FIG. 7 is a pair of a main microphone 62 having a forward narrow directivity using an acoustic tube 61 and a pair arranged in the vicinity of the rear end of the acoustic tube 61 and brought close to each other in opposite directivity directions. Between the unidirectional sub-microphone (the first sub-microphone 63a having the rear unidirectional characteristic and the third sub-microphone 63c having the anterior unidirectional characteristic) and the first sub-microphone 63a and the third sub-microphone 63c. It includes a second sub-microphone 63b having omnidirectional arrangement, a fourth sub-microphone 63d having rear unidirectional characteristics arranged near the tip of the acoustic tube 61, and a signal processing unit 64. The signal processing unit 64 includes a first filter 641, a second filter 642, a third filter 643, a fourth filter 644, a fifth filter 645, a delayer 646, an adder 647a, 647b, 649, and a variable attenuator 648a, 648b. To prepare for.

Here, the first to fourth sub-microphones 63a to 63d in the directional microphone 60 of the sixth embodiment are configured in the same manner as the first to fourth microphones 53a to 53d of the directional microphone 50 of the fifth embodiment, respectively. To.

Further, regarding the line microphone in which the main microphone 62 and the acoustic tube 61 in the directional microphone 60 of the sixth embodiment are combined, the main microphone 52 and the acoustic tube 51 in the fifth embodiment are also configured. It can be similar to a line microphone. Therefore, the acoustic tube 61 is formed in the shape of a cylinder or a square cylinder having a predetermined length for obtaining narrow angle directivity only at high frequencies, and has a plurality of openings 61a for phase interference on its side surface at regular intervals. ing.

That is, the directional microphone 60 of the sixth embodiment is configured as a narrow directional microphone having narrow directivity in the front direction of the back surface and side sensitivity suppression type as the processing of the signal processing unit 64, as in the fifth embodiment. However, in addition to this, as described below, the back sensitivity suppression amount and the side sensitivity suppression amount are configured to be adjustable by the user.

The output signal of the main microphone 62 is amplified by an amplifier and subjected to A / D conversion processing by an analog / digital (A / D) converter (the amplifier and the A / D converter are not shown). It is input to the delay device 646 in the signal processing unit 64. Similarly, each output signal of the first to fourth sub microphones 63a to 63d is also amplified by an amplifier and subjected to A / D conversion processing by an A / D converter (amplifier and A / D conversion). (Not shown in the device) are input to the first to fourth filters 641 to 644 in the signal processing unit 64, respectively.

However, the output signal subjected to the A / D conversion processing of the first sub microphone 63a is also input to the fifth filter 645.

The first filter 641 applies a filter process to cancel the lateral response of the main microphone to the digital output signal obtained from the first sub microphone 63a, and outputs the digital output signal to the adder 647a.

The second filter 642 applies a filter process to cancel the lateral response of the main microphone to the digital output signal obtained from the second sub microphone 63b, and outputs the digital output signal to the adder 647a.

The third filter 643 applies a filter process to cancel the lateral response of the main microphone to the digital output signal obtained from the third sub microphone 63c, and outputs the digital output signal to the adder 647a.

The fourth filter 644 performs a filter process for canceling the response in the back direction of the main microphone to the digital output signal obtained from the fourth sub microphone 63d, and outputs the digital output signal to the adder 647b.

The fifth filter 645 performs a filter process for canceling the response in the back surface direction of the main microphone to the digital output signal obtained from the first sub microphone 63a, and outputs the digital output signal to the adder 647b.

The adder 647a generates a sideways cancel signal for suppressing side sensitivity by inputting and adding each digital output signal obtained through the first to third filters 641 to 643, respectively, and is a variable attenuator. Output to 648a.

The adder 647b generates a rearward cancel signal for suppressing the backside sensitivity by inputting and adding each digital output signal obtained through the fourth and fifth filters 644, 645, respectively, and is a variable attenuator. Output to 648b.

The variable attenuator 648a makes it possible to adjust the amplitude of the sideways cancel signal obtained from the adder 647a by the suppression amount adjustment signal Vat1, and outputs the amplitude-adjusted sideways cancel signal to the adder 649. The suppression amount adjustment signal Vat1 is output from a volume regulator (not shown) that can be adjusted by the user.

The variable attenuator 648b makes it possible to adjust the amplitude of the rearward canceling signal obtained from the adder 647b by the suppression amount adjusting signal Vat2, and outputs the amplitude-adjusted rearward canceling signal to the adder 649. The suppression amount adjustment signal Vat2 is output from a volume adjuster (not shown) that can be adjusted by the user.

The delay device 646 performs delay processing on the digital output signal obtained from the main microphone 62 so as to compensate for the delay amount generated by the filter processing by the first to fifth filters 641 to 645, and outputs the delay process to the adder 649. ..

The adder 649 includes a digital output signal of the main microphone 62 obtained via the delay device 646, an amplitude-adjusted sideways cancel signal obtained from the variable attenuator 648a, and an amplitude-adjusted rearward cancel signal obtained from the variable attenuator 648b. By inputting and adding signals, a sound pickup signal with adjustable back and side sensitivity suppression is generated and output to the outside. Here, although it is decided that the output signal of the main microphone 62 passes through the delay device 646, it may be a digital filter that compensates for the frequency characteristic in the front direction instead of the delay device.

Here, as the filter processing relating to the first to third filters 641 to 643, the design method of the filter processing for suppressing the side sensitivity in the above-mentioned fourth embodiment can be used as it is, and the fourth and fifth filters 644,645 can be used as they are. As the filter processing related to the above, the design method of the filter processing for suppressing back sensitivity in the first embodiment described above can be used as it is. Therefore, the adder 647a can generate a side-to-side cancel signal to suppress the side-side sensitivity, and the adder 647b can generate a back-to-back cancel signal to suppress the back-to-back sensitivity.

Since the variable attenuators 648a and 648b are provided, the suppression amount of the back surface and side sensitivity can be individually adjusted as the sound pick-up signal output from the signal processing unit 64.

8 (a) to 8 (k) show 0 ° ≤ θ ≤, respectively, where θ = 0 ° is the directional direction (front front direction) of the main microphone 62 in the directional microphone 60 according to the sixth embodiment of the present invention. It is a figure which shows the simulation result of the sensitivity directivity about 360 ° (that is, 0 ° ≦ | θ | ≦ 180 °). In particular, FIG. 8 shows a simulation result of the sensitivity directional characteristic of a line microphone having a 20 cm long acoustic tube 61, which is obtained by applying back and side sensitivity suppression processing to a frequency band of 4 kHz or less.

In FIGS. 8 (a) to 8 (k), the characteristic of D1 shown is a sensitivity-oriented characteristic when the back surface and side surface sensitivity suppression processing is not applied, and the characteristic of D2 shown is the back surface and side surface sensitivity suppression. This is the sensitivity-oriented characteristic when processing is applied. In particular, it can be seen that the back and side sensitivities are preferably suppressed even in the frequency band of 4 kHz or less where the back and side sensitivities are likely to appear.

As described above, according to the directional microphone according to the present invention, for example, since the conventional back-sensitivity suppression type microphone cannot be finely adjusted for each frequency, the problem that the band that can be suppressed with high accuracy is limited is solved. be able to. In particular, when a line microphone is used as the main microphone, the conventional technique can obtain the back sensitivity suppressing effect only in the low frequency band where the influence of the acoustic tube is small, so let's positively obtain the back sensitivity suppressing effect. In this case, it had to be applied to a line microphone with a short acoustic tube (for example, 45 mm).

On the other hand, according to the directional microphone according to the present invention, since finer optimization can be performed for each frequency, the back sensitivity suppression effect can be obtained even in the middle to high band where the influence of the acoustic tube is large. It is also possible to use a line microphone using a longer acoustic tube, and a narrow directional microphone having a narrower directivity can be configured.

Further, according to the directional microphone according to the present invention, it is possible to solve the problem that the side sensitivity cannot be sufficiently suppressed at a low frequency with a line microphone using a short acoustic tube, and it is possible to construct a line microphone with a sharper directivity. ..

Further, according to the directional microphone according to the present invention, since the suppression amount of the back surface and side sensitivity can be adjusted individually, it can be applied not only to the application by means operation but also to the video camera with the variable directional microphone. ..

[Video camera with variable directional microphone]
FIG. 9 shows an outline of a video camera 100 with a variable directional microphone according to the present invention, which uses the directional microphone 60 according to the sixth embodiment of the present invention and enables the directivity to be changed according to a zoom. It is a figure which shows the structure.

The video camera 100 with a variable directional microphone includes a directional microphone 60 according to a sixth embodiment of the present invention, an optical lens 110 with a zoom function, an image pickup control unit 111 including an image pickup element, an output unit 112, and sound collection control. A unit 113 is provided.

The image pickup control unit 111 receives a user's operation instruction and outputs a zoom control signal to the optical lens 110 with a zoom function to perform a zoom operation for determining the angles of view θ _V1 to θ _V2 , and the subject is subjected to this zoom operation. The signal of the image of the image captured is output to the output unit 112.

The zoom control signal output from the image pickup control unit 111 is also input to the sound collection control unit 113.

When a zoom control signal for performing a zoom operation having an angle of view θ _V1 to θ _V2 is input, the sound collection control unit 113 increases the directivity and the amount of suppression of the rear and side sensitivity when the angle of view is narrow. The suppression amount adjustment signals Vat1 and Vat2 are output to the directional microphone 60, and when the angle of view is wide, the suppression amount adjustment signals Vat1 and Vat2 that reduce the suppression amount of the rear and side sensitivity are transmitted to the directional microphone 60. Output.

The directional microphone 60 generates a sound pickup signal in which the suppression amount of the rear surface and side sensitivity is automatically adjusted according to the zoom control signal, and outputs the sound pickup signal to the output unit 112.

The output unit 112 displays and reproduces the video and the sound pick-up signal corresponding to the zoom control signal to the display / reproduction unit (not shown).

As a result, the video camera 100 with a variable directional microphone has a configuration in which the directivity of the directional microphone 60 can be automatically changed by suppressing the sensitivity of both the rear surface and the side surface with high accuracy according to the zoom.

Therefore, according to the video camera 100 with a variable directional microphone according to the present invention, it is possible to suppress ambient noise other than the sound emitted by the subject with high accuracy in accordance with the close-up of the subject of interest.

The directional microphone and the video camera with a variable directional microphone according to the present invention are not limited to the examples of the above-described embodiments, but are limited only by the description of the claims.

According to the present invention, it is possible to configure a directional microphone that suppresses the sensitivity in a predetermined directional direction with high accuracy over a wide band, and a video camera with a variable directional microphone, which is useful for applications of a microphone having directivity. Is.

10, 20, 30, 40, 50, 60 Directional microphones 11,21,41,51,61 Sound tubes 11a, 21a, 41a, 51a, 61a Openings 12, 22, 42, 52, 62 Main microphones 13a, 23a, 43a, 53a, 63a 1st sub-microphone 13b, 23b, 43b, 53b, 63b 2nd sub-microphone 43c, 53c, 63c 3rd sub-microphone 53d, 63d 4th sub-microphone 14, 24, 34, 44, 54, 64 signals Processing unit 33a 1st microphone 33b 2nd microphone 33c 3rd microphone 141,241,341,441,541,641 1st filter 142,242,342,442,542,642 2nd filter 245,343,443,543 643 3rd filter 544,644 4th filter 645 5th filter 145,445,545,646 Delayer 146,246,346,446,546,647a, 647b, 649 Adder 648a, 648b Variable attenuator 100 Variable directional Video camera with microphone 110 Optical lens with zoom function 111 Imaging control unit 112 Output unit 113 Sound collection control unit

Claims (7)

A directional microphone with anterior narrow directivity that suppresses back sensitivity.
A main microphone with narrow forward directivity using an acoustic tube,
At least one sub-microphone arranged along the longitudinal direction of the acoustic tube and having unidirectionality in the direction opposite to the frontal direction forming the main axis of the anterior narrow directivity.
The amount of delay generated by the filtering of the output signal obtained from the at least one sub-microphone and the output signal obtained from the main microphone and the signal subjected to the filtering process for canceling the response on the back surface of the main microphone. It is provided with a signal processing unit that generates a sound pickup signal with suppressed back sensitivity by adding a signal that has been delayed processed so as to compensate for the above.
The signal processing unit
The output signal vector M (ω) after the delay processing of the main microphone and the transmission function vector W (ω) of the filtering processing are used to filter the output signal vector G (ω) of the at least one sub-microphone. The final output vector Y (ω) at an arbitrary frequency ω from the front direction where the main axis θ = 0 ° of the forward narrow directionality obtained by adding the obtained digital output signals to the back direction where θ = 180 ° is formed, and , Θ = 0 °, while maintaining the sensitivity in the front direction, the final output vector Y (ω) is used to suppress the sensitivity in the back direction, which is θ = 180 °. A directional microphone characterized by performing a filtering process that minimizes the difference between the target characteristic vector D (ω) and the target characteristic vector D (ω) based on a predetermined norm. A directional microphone with donut-shaped directivity,
A pair of unidirectional microphones that are close to each other with opposite directivity directions,
An omnidirectional microphone having omnidirectionality arranged between the pair of unidirectional microphones,
A donut-shaped directivity is obtained by performing a predetermined addition / subtraction process using a signal obtained by filtering the pair of unidirectional microphones and a signal obtained by filtering the omnidirectional microphone. A signal processing unit that generates a pick-up signal to have, and
A directional microphone characterized by being equipped with. A directional microphone with anterior narrow directivity that suppresses lateral sensitivity.
A main microphone with narrow forward directivity using an acoustic tube,
A pair of unidirectional objects arranged along the longitudinal direction of the acoustic tube and brought close to each other in the same direction and opposite directions to the front direction forming the main axis of the anterior narrow directivity. With a microphone
An omnidirectional microphone having omnidirectionality arranged between the pair of unidirectional microphones,
A filtered signal that cancels the lateral response of the main microphone to each output signal obtained from the pair of unidirectional microphones and the omnidirectional microphone, and an output signal obtained from the main microphone. On the other hand, a signal processing unit that generates a sound pickup signal with suppressed side sensitivity by adding a signal that has been delayed so as to compensate for the delay amount generated by the filter processing.
A directional microphone characterized by being equipped with. The signal processing unit
The output signal vector M _side (ω) after the delay processing of the main microphone and the transmission function vector W _side (ω) of the filtering processing make the pair of unidirectional microphones and the output signal vector of the omnidirectional microphone. The front direction that makes the main axis θ = 0 ° of the forward narrow directionality obtained by adding the digital output signal obtained by filtering G _side (ω), and 0 ° <| θ | <180 °. The final output vector Y (ω) at an arbitrary frequency ω in the lateral direction that makes θ = 180 ° and the back direction that makes θ = 180 °, and the sensitivity in the front direction that makes θ = 0 ° and the sensitivity in the back direction that makes θ = 180 °. The final output vector Y (ω) and the target are used by using the target characteristic vector D _side (ω) for suppressing the sensitivity in the lateral direction, which is 0 ° << | θ | <180 ° while maintaining the sensitivity. The directional microphone according to claim 3 , wherein the directional microphone is subjected to a filtering process that minimizes the difference from the characteristic vector D _side (ω) based on a predetermined norm. A directional microphone with anterior narrow directivity that suppresses back and side sensitivity.
A main microphone with narrow forward directivity using an acoustic tube,
A pair of unidirectional objects arranged along the longitudinal direction of the acoustic tube and brought close to each other in the same direction and opposite directions to the front direction forming the main axis of the anterior narrow directivity. With a microphone
An omnidirectional microphone having omnidirectionality arranged between the pair of unidirectional microphones,
A unidirectional sub-microphone arranged along the longitudinal direction of the acoustic tube and oriented in a direction opposite to the front direction forming the main axis of the anterior narrow directivity.
Each output signal obtained from the pair of unidirectional microphones, the omnidirectional microphone, and the sub microphone is filtered to cancel the sideways and backside responses of the main microphone, and the signal. A signal processing unit that generates a sound pick-up signal with suppressed back and side sensitivities by adding a signal that has been delayed to compensate for the delay caused by the filter processing to the output signal obtained from the main microphone.
A directional microphone characterized by being equipped with. A directional microphone with anterior narrow directivity that can adjust the amount of suppression of back and side sensitivities.
A main microphone with narrow forward directivity using an acoustic tube,
A pair of unidirectional objects arranged along the longitudinal direction of the acoustic tube and brought close to each other in the same direction and opposite directions to the front direction forming the main axis of the anterior narrow directivity. With a microphone
An omnidirectional microphone having omnidirectionality arranged between the pair of unidirectional microphones,
A unidirectional sub-microphone arranged along the longitudinal direction of the acoustic tube and oriented in a direction opposite to the front direction forming the main axis of the anterior narrow directivity.
A filtered signal is added to each output signal obtained from the pair of unidirectional microphones and the omnidirectional microphone to generate a sideways cancel signal for suppressing the side sensitivity of the main microphone. The output obtained from the pair of unidirectional microphones, the unidirectional microphone having a direction opposite to the front direction forming the main axis of the front narrow directional, and the sub microphone. A filtered signal is added to the signal to generate a backside cancel signal to suppress the backside sensitivity of the main microphone.
The amplitude of the lateral cancel signal is adjusted based on an external instruction, the amplitude of the rear cancel signal is adjusted based on an external instruction, and the output signal obtained from the main microphone is used. A signal processing unit that generates a sound pickup signal that can individually adjust the suppression amount of the rear and side sensitivity by adding the signals that have been delayed so as to compensate for the delay caused by the filter processing.
A directional microphone characterized by being equipped with. A video camera with a variable directional microphone
The directional microphone according to claim 6 and
An optical lens with a zoom function and
An imaging control unit that outputs a zoom control signal to the optical lens with a zoom function based on an external instruction to perform a zoom operation for determining an angle of view, and generates a signal of an image obtained by imaging the subject through the zoom operation. ,
Based on the zoom control signal, when the angle of view is narrow, the directivity suppresses the back and side sensitivity, and when the angle is wide, the directivity suppresses the back and side sensitivity. A sound pickup control unit that outputs an adjustment signal to the directional microphone and controls the directional microphone to generate a sound pickup signal in which the suppression amount of the rear and side sensitivity is automatically adjusted according to the zoom control signal.
A video camera with a variable directional microphone that features.

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