JPH0690492A - Voice input device - Google Patents

Abstract

PURPOSE:To realize ultra-directivity by which the sensivity in directions other than a desired voice incoming direction can be lowered further than a microphone of a single directivity by a simple constitution by providing two microphones, a delay circuit and a subtraction circuit. CONSTITUTION:A first microphone 11 and a second microphone 21 are arranged at intervals of a space d. The both of the microphones 11, 21 are composed of microphones of a single directivity and are installed so that the directivity axis may face the orthogonal direction to the array direction of the two microphones 11, 21 and the direction where sensitivity is high may face a prescribed direction. In a subtraction circuit 13, the output of the first microphone 11 and the output that the output of the second microphone 21 is delayed in a delay circuit 23 are synthesized. Thus, a voice input device having the directivity that the sensivity in a lateral direction for the directivity axis is made lower further than usual can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice input device using a plurality of microphones.

[0002]

2. Description of the Related Art For example, as an audio input device used for a VTR with a built-in camera, it is desired to pick up only the sound from the direction of the object and remove the sound from the side of the photographer or from other directions. .

As described above, as a voice input device for picking up only a voice input from a specific direction, a unidirectional microphone as shown in FIG. 14 is generally used.

[0004]

However, the above-mentioned unidirectional microphone has relatively high sensitivity in directions other than the incident direction having the highest sensitivity. Therefore, even if the line connecting the highest sensitivity position and the null sensitivity position (this is referred to as the directional axis) is oriented toward the desired voice direction,
As is clear from the characteristic diagram of No. 4, when the input direction of the unnecessary voice is lateral to the desired voice input direction, the voice is picked up at a size of, for example, 1/2 (-6 dB) as compared with the desired voice. Will be done.

In view of the above points, the present invention has a super directivity in which the sensitivity in directions other than the desired voice arrival direction can be made even lower than that of a unidirectional microphone.
An object is to provide a voice input device that can be realized with a simple configuration.

[0006]

In order to solve the above-mentioned problems, the voice input device according to the present invention is arranged such that the first and second voice input devices are arranged a predetermined distance apart from each other when the reference numerals of the embodiments described later correspond to each other. Of the microphone, a delay circuit that delays the output signal of the second microphone, and a subtraction circuit that subtracts the output signal of the delay circuit from the output signal of the first microphone. It is characterized by having been obtained.

[0007]

In the above structure, the output of the first microphone and the output of the second microphone delayed by the delay circuit are combined in the subtraction circuit, and the sensitivity in the lateral direction with respect to the directional axis is As a result, a voice input device with a lower directivity than that of the related art is realized.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some embodiments of a voice input device according to the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the present invention, in which a first microphone 11 and a second microphone 12 are arranged at a distance d. These microphones 11 and 1
As shown in FIG. 2, both 2 are composed of unidirectional microphones, and the direction of the directional axis z thereof is in a direction orthogonal to the arrangement direction of these two microphones 11 and 12. It is installed so that the direction with high sensitivity is facing the left side of the figure.

The sound signal picked up by the microphone 11 and converted into an electric signal is supplied to the subtraction circuit 13 via the amplifier 12. Further, the audio signal picked up by the microphone 21 and converted into an electric signal is supplied to the delay circuit 23 via the amplifier 22 and delayed, and the delayed signal is supplied to the subtraction circuit 13. Then, the subtraction output from the subtraction circuit 13 is led to the output terminal 14 as the output of the device.

In this example, the delay amount of the delay circuit 23 is
The distance d between the two microphones 11 and 21 is determined in consideration of the time during which the sound propagates. This value is preferably selected to be not more than twice d / c, where c is the sound propagation velocity. In this example, the delay amount of the delay circuit 23 is selected to be equal to d / c.

In this case, the arrow AR in FIG.
As shown in FIG. 3, when considering the component of the sound SA coming from the microphone 11 side in the arrangement direction of the two microphones 11 and 21, this sound SA is
And the sound SA is input to both the microphones 21 and the sound SA input to the microphones 11 is delayed by the delay time d / c corresponding to the distance d between the microphones 11 and 21.
The sound SA input to the microphone 21 is delayed.
Moreover, the output audio signal of the microphone 21 is further delayed by the delay circuit 23. Therefore, as the input signal of the subtraction circuit 13, the sound SA components in the output sound of the microphone 11 and the output sound of the microphone 21 become signals that are considerably deviated in terms of timing and become uncorrelated. Therefore, even if the subtraction circuit 13 subtracts the output signal of the delay circuit 235 from the output audio signal of the microphone 11, the direction A
The voice SA component from R is hardly reduced.

On the other hand, the sound SB coming from the direction AL opposite to the direction AR is also picked up by the microphone 11 and the microphone 21, but the microphone 11 and the microphone 2
Since it is arranged at a distance d from 1, the sound SB input to the microphone 11 is different from the sound SB input to the microphone 21 by the delay time d / c corresponding to the arrival direction of the sound SB. Be delayed. However, since the output voice signal of the microphone 21 is delayed by the delay circuit 23 by the same delay time, the component of the voice SB arriving from the direction AL becomes the time shift as the input of the subtraction circuit 13. The subtraction circuit 13 cancels.

That is, in the case where the voice arrival direction is 180 ° different from the direction AR, that is, in the case of the direction AL in FIG. 3, the voice input to the microphone 11 is different from the voice input to the microphone 21. Just delay by d / c. In the subtraction circuit 13, the audio component in this direction is canceled because there is no time lag between the audio signal component from the first microphone 11 side and the audio signal component from the second microphone 21 side.

Next, in the case where the voice comes from diagonally rearward as indicated by'in FIG. 3, assuming that the incident angle of the voice with respect to the direction AR is θ, the voice reaches the microphone 21 and then the microphone. Since the time to reach 11 is d · cos θ / c, it is shorter than in the case of the direction. Therefore, the audio component from this direction, ', during the two inputs of the subtraction circuit 13 is at that time d.
The time difference is between the cos θ / c and the delay time d / c of the delay circuit 23. Therefore, the amount of cancellation in the subtraction circuit 13 is small.

Further, in the case where the voice is a voice component coming from the lateral direction indicated by'in FIG. 3, the delay between the input time of the microphone 11 and the input time of the microphone 21 of the voice is small. . Therefore, the difference from the delay amount of the delay circuit 23 becomes large, and the cancel amount becomes smaller.

FIG. 4 is a diagram for explaining the basic principle configuration of the present invention. That is, as shown in FIG. 4, when plane waves P1 and P2 arrive at positions separated by a distance d at an incident angle θ with respect to the direction AR, P2 = P1 · Exp (−jωd · cos θ / c) ( 1) Then, P2d obtained by adding a delay to P2 becomes P2d = P2 · Exp (−jωnT) (2) (T: sampling interval of audio signal). Therefore, P = P1−P2d = P1 (1−Exp (−j (ωnT + ωd · cos θ / c))) (3) Here, for example, when the unnecessary voice comes from the direction of FIG. 5, that is, when θ = 180 °,
Since nT such that P = 0 is nT = d / c, P = P1 (1-Exp (-jω (d / c) (1 + cosθ))) (4).

In the example of FIG. 1, as shown in FIG. 2, the unidirectional equation in which the directional axis of the microphone is directed to the left side is represented by 1-sin θ, and therefore the equation (4) is used. From the output P of the example of FIG.
out becomes Pout = (1-sin θ) × (1-Exp (−jω (d / c) (1 + cos θ))) (5).

A graph of this equation for θ is shown in FIG.
The directivity is as shown in. That is, the directional axis direction is tilted counterclockwise by 45 ° with respect to the direction AR. If the voice in the directional axis inclined by 45 ° with respect to the direction AR is the desired voice direction (for example, this direction is the front direction), the sensitivity to the sound from the back direction (lower right in the figure) opposite to the front direction. Is very low, and the sound coming from the left and right lateral directions with respect to the front direction is about 1/6 (about -16 dB) as compared with the sound coming from the front direction. That is, it is possible to realize a so-called super-directional voice input device in which the front sensitivity is much higher than the side sensitivity as compared with the conventional one.

FIG. 7 shows an example in which a voice input device for picking up left and right two-channel stereo voice is realized by combining two devices of the example of FIG. In FIG. 7, the microphone 11R is for sound collection of the right channel,
The microphone 11L is for collecting the sound of the left channel, and the both microphones 11R and 11L are arranged at a distance d. Also, these microphones 11R and 1
1L is similar to the example of FIG. 1 described above, as shown in FIG.
Both of them are composed of a unidirectional microphone, and the direction of the directional axis thereof is the direction orthogonal to the arrangement direction of these two microphones 11R and 11L, and the direction of high sensitivity is shown in FIG. It is installed so that it faces the left side of.

First, the structure of the right channel audio signal will be described. The right channel audio signal obtained by being picked up by the microphone 11R and converted into an electric signal is supplied to the subtraction circuit 13R via the amplifier 12R. To be done.

An unnecessary sound signal for the sound of the right channel, which is picked up by the microphone 11L and converted into an electric signal, is supplied to the delay circuit 23R via the amplifier 12L, and the delay circuit 23R delays it. The output signal is supplied to the subtraction circuit 13R. The output signal of the subtraction circuit 13R is led to the output terminal 14R. Delay circuit 2
The delay amount of 3R is selected to have exactly the same relationship as the delay amount of the delay circuit 23 in the example of FIG.

The directional characteristics of the output signal obtained at the output terminal 14R at this time are as shown in FIG. That is, in FIG. 7, the output terminal 14 is configured such that the 45 ° direction diagonally upward to the left as indicated by the arrow aR is the audio arrival direction of the right channel.
A right channel audio signal is obtained at R.

Next, the structure of the left channel audio signal will be described. The left channel audio signal obtained by being picked up by the microphone 11L and converted into an electric signal is sent to the subtraction circuit 13L via the amplifier 12L. Supplied.

The unnecessary sound signal for the sound of the left channel from the microphone 11R is supplied to the delay circuit 23L via the amplifier 12R, and this delay circuit 23L is supplied.
The delayed output signal of is supplied to the subtraction circuit 13L. The output signal of the subtraction circuit 13L is led to the output terminal 14L.
The delay amount of the delay circuit 23L is also selected to have exactly the same relationship as the delay amount of the delay circuit 23 in the example of FIG.

The directional characteristic of the output terminal obtained at the output terminal 14L at this time is as shown in FIG. 6, and the direction of the directional axis is shifted by 135 ° with respect to the direction AR. That is, in FIG.
A left channel audio signal is obtained at the output terminal 14L with the direction of ° as the incoming direction of the audio of the left channel. Therefore, according to the example of FIG. 7, an output audio signal obtained by collecting audio from a direction having an opening angle of about 90 ° as 2-channel stereo audio is obtained.

Next, regarding the directional characteristic of the output signal from the voice input device of the example of FIG. 1, the direction of the directional axis is changed by providing a gain difference between the output voice signals of the two microphones 11 and 12. You can FIG. 8 shows a configuration example in that case.

That is, in this example, the output signal of the microphone 11 is the amplifier 12 and the gain adjusting circuit 3.
It is supplied to the subtraction circuit 13 via 1. The gain adjustment circuit 31 is changed by the gain adjustment signal input via the adjustment signal input terminal 32. Otherwise, the configuration is exactly the same as in the example of FIG.

In the configuration of FIG. 8, the gain of the gain adjusting circuit 31 is changed by the adjusting signal, so that the gain of the output signal of the microphone 11 calculated by the subtracting circuit 13 and the delayed signal of the output signal of the microphone 12 are calculated. Of the directional characteristic changes, and thus the direction of the directional axis of the directional characteristic is changed.

That is, the gain G of the gain adjusting circuit 31
However, when G = 1, the gain ratio of the two input signals of the subtraction circuit 13 is 1: 1. Therefore, as shown in FIG. 9A, the characteristic becomes the same as the characteristic shown in FIG. Is
It is inclined by 45 ° with respect to the direction AR.

The gain G of the gain adjusting circuit 31 is 1 <G
When <2, the output signal gain of the microphone 11 among the two input signals of the subtraction circuit 13 becomes high, and the directional characteristic of the output signal is inclined by 45 ° or more with respect to the direction AR as shown in FIG. 9B. It becomes a state. And the gain G
When = 2, as shown in FIG. 9C, the directivity characteristic of the output signal is inclined by 90 ° with respect to the direction AR. That is, by changing the gain G of the gain adjusting circuit 31 from 1 to 2, the direction of the directional axis is set to 4 with respect to the direction AR.
It can be changed from 5 ° to 90 °.

Although the gain adjusting circuit 31 is inserted into the output signal of the microphone 11, the gain adjusting circuit may be provided before or after the delay circuit 23 on the output side of the microphone 21. Further, the gain adjusting circuit may not only increase the gain but also decrease the gain.

FIG. 10 shows an example in which the direction of the directional axis of each channel output is changed in the embodiment of the audio input device for obtaining the left and right two-channel stereo audio signals.

That is, in the example of FIG. 10, for the audio output of the right channel, the amplifier 12R of the example of FIG.
The gain adjustment circuit 31R is inserted between the subtraction circuit 13R and the subtraction circuit 13R, and the gain adjustment signal from the terminal 32R is input.
By this gain adjustment, the directional axis of the right channel audio output can be changed. Further, for the audio output of the left channel, the gain adjustment circuit 31L is inserted between the amplifier 12L and the subtraction circuit 13L, and the gain adjustment signal from the terminal 31L is input. By this gain adjustment, the directional axis of the audio output of the left channel can be changed.

Next, in the example of FIG. 1, by changing the delay amount of the delay circuit 23, it is possible to change the sensitivity ratio on the left and right of the directivity characteristic of the output signal with the directivity axis as a boundary. FIG. 11 shows an example of that case, and a variable delay circuit 41 is provided between the amplifier 22 and the subtraction circuit 13. Then, the delay amount adjustment signal is input from the input terminal 42.

As described above, when the delay amount DL of the variable delay circuit 41 is made equal to the distance d between the two microphones 11 and 21 at the time when the sound propagates, that is, DL = d.
When / c, as shown in FIG. 12A, the characteristic is symmetrical with respect to the directional axis inclined by 45 ° with respect to the direction AR,
The sensitivities to voices coming from the left and right with respect to the directional axis are equal. On the other hand, when the delay amount DL of the variable delay circuit 41> d / c, as shown in FIG. 12B,
The direction of the directional axis is almost unchanged, but the sensitivity on the right side of this directional axis is greater than the sensitivity on the left side. When the delay amount DL of the variable delay circuit 41 is smaller than d / c, as shown in FIG. 12C, the direction of the directional axis is almost unchanged, but the sensitivity on the left side of this directional axis is larger than the sensitivity on the right side. In addition,
As described above, the delay amount DL is preferably within 2 · d / c.

FIG. 13 shows an embodiment of the audio input device for obtaining the above-mentioned left and right two-channel stereo audio signals.
This is the case when the example of is applied. That is, a variable delay circuit 41R is connected instead of the delay circuit 23R in the example of FIG.
The delay amount is adjusted by the delay amount adjusting signal from the terminal 42R. A variable delay circuit 41L is connected instead of the delay circuit 23L in the example of FIG. 7, and the delay amount is adjusted by a delay amount adjustment signal from the terminal 42L.

In this configuration, the variable delay circuit 23
By adjusting the delay amounts of R and 23L, the opening angle of 90 ° between the left and right channels does not change, but the sensitivity ratio of the directional characteristic of the output of each channel to the voice coming from the left and right directions changes. , The left and right channel crosstalk amount can be changed. That is,
Since the crosstalk amount of the left and right channels can be changed while maintaining the directivity axis in a fixed direction, a stable stereo feeling can always be obtained.

In the above description, the analog signal processing is explained, but the digital signal processing can be easily adopted.

[0040]

As described above, according to the present invention, it is possible to realize superdirectivity with a simple structure, which can sufficiently lower the lateral sensitivity with respect to the desired voice arrival direction. You can According to the present invention, a 2-channel stereo audio input device having an opening angle of 90 ° can be realized with a simple structure.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a voice input device according to the present invention.

FIG. 2 is a diagram for explaining two microphones used in the example of FIG.

FIG. 3 is a diagram showing a voice arrival direction used for explaining the operation of the example of FIG. 1;

FIG. 4 is a diagram showing a basic configuration of the present invention.

5 is a diagram showing an example of directional characteristics of output in the example of FIG.

FIG. 6 is a diagram showing an example of output directional characteristics in the example of FIG. 1;

FIG. 7 is a block diagram of an embodiment of a stereo voice input device of the present invention.

FIG. 8 is a block diagram of another embodiment of the present invention.

9 is a diagram showing an example of directional characteristics according to the operation of the example of FIG.

FIG. 10 is a block diagram showing an example in which the example of FIG. 8 is applied to a stereo voice input device.

FIG. 11 is a block diagram of still another example of the present invention.

12 is a diagram showing an example of directional characteristics according to the operation of the example of FIG.

FIG. 13 is a block diagram showing an example in which the example of FIG. 11 is applied to a stereo voice input device.

FIG. 14 is a diagram showing unidirectionality of a microphone.

[Explanation of symbols]

 11 First Microphone 11R Right Channel Microphone 11L Left Channel Microphone 13 Subtraction Circuit 14 Output Terminal 21 Second Microphone 23 Delay Circuit 31 Gain Adjustment Circuit 32 Gain Adjustment Signal Input Terminal 41 Variable Delay Circuit 42 Delay Amount Adjustment Signal Input Terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaoru Gyotoku 6-735 Kitashinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (8)

[Claims] 1. A first microphone and a second microphone arranged at a predetermined distance, a delay circuit for delaying an output signal of the second microphone, and a delay circuit for outputting an output signal of the first microphone. And a subtraction circuit for subtracting the output signal of the above, and an output signal is obtained from the subtraction circuit. 2. The voice input device according to claim 1, wherein the first and second microphones are both unidirectional microphones. 3. The first and second microphones are both unidirectional microphones, and the first and second microphones are unidirectional microphones.
The voice input device according to claim 1, wherein the directional axes of the first and second microphones are arranged so as to be oriented in a direction orthogonal to the arrangement direction of the two microphones. 4. A first microphone and a second microphone which are arranged apart from each other by a predetermined distance, a first delay circuit which delays an output signal of the first microphone, and an output signal of the second microphone. A second delay circuit that delays; a first subtraction circuit that subtracts the output signal of the second delay circuit from the output signal of the first microphone; and a first subtraction circuit that outputs the output signal of the second microphone from the first delay circuit. A second subtraction circuit for subtracting the output signal of the delay circuit, wherein the first and second microphones are both unidirectional microphones, and the directional axes of the first and second microphones Is arranged so as to face in a direction orthogonal to the array direction of these two microphones, and the first and second output signals are obtained from the first and second subtraction circuits. 5. The voice input device according to claim 1, wherein the delay circuit is a variable delay circuit. 6. The voice input device according to claim 4, wherein the first and second delay circuits are variable delay circuits. 7. The means according to claim 1, further comprising means for providing a relative gain difference between the output signal of the first microphone and the output signal of the second microphone which are subtracted by the subtraction circuit, A voice input device in which the gain difference is variable. 8. The means for providing a relative gain difference between the output signal of the first microphone and the output signal of the second microphone which are subtracted by the first subtraction circuit according to claim 2. And a means for providing a relative gain difference between the output signal of the second microphone and the output signal of the first microphone which are subtracted by the second subtraction circuit, and A voice input device in which the gain difference is variable.