JPH09149490A - Microphone device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To show strong directivity by automatically switching whether to output only the output signal of a first microphone or to output the difference signal between first and second microphones so as to prevent the increase of the sound gathering quantity of surrounding random noise to reduce the output of sound generated from the direction except for that of a speaking person. SOLUTION: When a judging device 31 judges that the surrounding random noise such as wind noise is large, a switching device 33 selects only output signal of a non-directional microphone 21 from an amplifier 27. On the other hand, when judging the surrounding random noise such as wind noise is small, the switching device 33 outputs a signal consisting of difference between the output signals from the non-directional microphones 21 and 22 from an adder 32. Then these outputs are automatically switched to prevent the increase of the sound gathering quantity of surrounding noise.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microphone device capable of exhibiting directivity, and more particularly to a microphone device capable of reducing the output of sounds other than the direction of the talker and reducing the volume of ambient noise. .

[0002]

2. Description of the Related Art Conventionally, as a microphone device of this type, there is one described in Japanese Utility Model Laid-Open No. 2-21997. It arranges two omnidirectional microphones in a straight line in the direction of extension of a straight line extending in the longitudinal direction. When the straight line extending in the longitudinal direction of the two omnidirectional microphones is configured to be the speaker direction, voices having different delays due to the time difference of the sound propagation caused by the difference in the perspective of the respective omnidirectional microphones. Is entered. The respective omnidirectional microphones to which voices with different delays are input output voice signals having a phase difference due to the difference in delay and are given to common output means.
The output means calculates the difference in amplitude due to the phase difference between the outputs of the two omnidirectional microphones, and outputs the difference signal to the speaker device.

FIG. 2 shows the conventional microphone device described above.
The configuration will be further described in detail with reference to FIG. 2 is 2
FIG. 3 is a diagram showing a configuration of a microphone device in which two omnidirectional microphones are arranged in a straight line in a longitudinal direction so as to have directivity. In FIG. 2, M1 and M2 are omnidirectional microphones, and 102 is an omnidirectional microphone M.
1, a housing that accommodates M2 in a straight line in the longitudinal direction, 101 is a directional axis on the axis passing through the omnidirectional microphones M1 and M2 arranged in the longitudinal direction, and 103 is a phase difference between the outputs of the two microphones M1 and M2. An operational amplifier that calculates and outputs a difference in amplitude, 104 is a buffer amplifier that amplifies the output of the operational amplifier, and 105 is a speaker that emits a voice, P1
Is an output terminal for outputting the output of the buffer amplifier 104 to a speaker device (not shown).

Next, the operation of the conventional microphone device will be described in detail with reference to FIG. First, when the speaker 105 produces a sound, the voice is first captured by the omnidirectional microphone M2 and then by the omnidirectional microphone M1. At that time, the omnidirectional microphone M2
The voice captured by the microphone is captured slightly earlier than the voice captured by the omnidirectional microphone M1. The respective outputs of the omnidirectional microphones M1 and M2 which are output with a phase difference corresponding to the delay difference due to the sound propagation are respectively the operational amplifier 10.
3 inputs and the difference between the two audio inputs is calculated in the operational amplifier 103. The difference in the audio input is amplified by the buffer amplifier 104 and output to the speaker device through the output terminal P1.

As described above, the difference between the two voice inputs is mainly derived from the speaker 105 by the two omnidirectional microphones M1 arranged in a straight line in the longitudinal direction along the directional axis.
It is caused by a time difference (phase difference) in arrival or propagation due to a difference in distance to M2. Therefore, the sounds emitted from the direction other than the speaker 105 in the directional axis and reaching the omnidirectional microphones M1 and M2 are input at substantially the same time (without a phase difference), and are deleted by the operational amplifier 103. As a result of the output being reduced, it is possible to reduce the sound collection volume of noise and the like generated from the lateral direction.

[0006]

However, in the above-mentioned conventional microphone device, two omnidirectional noises are used for ambient noise having high directionality, such as wind noise, which has no directivity and whose source is not determined. Since there is a large difference in the microphone output, not only does the noise output from the operational amplifier not decrease, but rather the noise output is greatly expanded compared to the case of collecting with one of the omnidirectional microphones.
There was a problem that the noise collection volume increased.

The present invention has been made in order to solve the above-mentioned conventional problems. When the ambient noise having a high randomness such as wind noise is high, the volume of the collected sound is prevented from increasing, while the direction of the speaker is increased. It is an object of the present invention to provide a microphone device capable of exhibiting strong directivity by picking up only the sound from the speaker and reducing the output of the sound emitted from the direction other than the direction of the talker.

[0008]

The microphone device according to the present invention uses two omnidirectional microphones whose longitudinal direction is aligned with the direction of the talker, and the output of one omnidirectional microphone is used. A low frequency component is extracted from the signal to determine its sound pressure level. When the sound pressure level is higher than a predetermined level, only the output signal of the one omnidirectional microphone is output, and when it is lower than the predetermined level, the one non-directional microphone is output. The output signal of the directional microphone and the opposite phase signal obtained by inverting the output signal of the other omnidirectional microphone are switched and used so as to be output.

According to the present invention, when the ambient noise having high randomness is high, only the output signal of one of the omnidirectional microphones is output to prevent an increase in the volume of collected ambient noise, and on the other hand, the randomness is high. When the ambient noise is low, only the sound from the direction of the talker is picked up, and the output of the sound emitted from the direction other than the direction of the talker can be reduced to obtain a strong directivity. .

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises first and second omnidirectional microphones arranged in a straight line with the longitudinal direction thereof facing the speaker, and the first omnidirectional microphone. Determination means for determining the sound pressure level of the low frequency component of the output signal collected by the omnidirectional microphone and outputting the determination result;
The output signal of the first omnidirectional microphone and the second signal
Of the output signal of the first omnidirectional microphone based on the determination result of the determination means and the difference signal output means for calculating the phase difference from the output signal of the omnidirectional microphone and outputting the difference signal. Switching means for switching between selecting and outputting, or selecting and outputting the difference signal between the output signals of the first and second omnidirectional microphones, and the switching means is provided based on the determination result of the determining means. It is configured to automatically switch between outputting only the output signal of the first omnidirectional microphone or outputting the difference signal of the output signals of the first and second omnidirectional microphones.
It has the effect of preventing an increase in the volume of ambient noise with a high degree of randomness such as wind noise, while reducing the output of the sound emitted from a direction other than the direction of the speaker to exert a strong directivity. .

According to a second aspect of the present invention, the determination means extracts a low frequency component from the output signal collected by the first omnidirectional microphone, and a low pass filter,
A sound pressure level calculator for calculating the sound pressure level of the extracted low frequency component, and comparing the calculated sound pressure level with a predetermined level, when the sound pressure level is higher than the switching means, It is instructed to output only the output signal of the first omnidirectional microphone, and when the sound pressure level is lower, a difference signal due to the phase difference between the output signals of the first and second omnidirectional microphones is output. The sound pressure level of the low-frequency component that contains a large amount of wind noise and a high degree of random ambient noise from the output signal of the omnidirectional microphone. Has an effect that it is possible to effectively determine whether to prevent the increase in the volume of ambient noise collected or to emphasize the directivity by determining the size of the.

According to a third aspect of the present invention, the difference signal output means inverts the phase of the output signal collected by the second omnidirectional microphone and outputs a reverse phase signal. And a phase difference between the collected output signals of the first and second omnidirectional microphones by adding the collected output signal of the first omnidirectional microphone and the inverted phase signal whose phase is inverted. And an addition means for outputting a difference signal according to the above, which outputs a difference signal composed of a phase difference between the output signals collected by the first and second omnidirectional microphones to output a strong directivity. It has the effect of being able to exhibit.

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings and FIG. FIG. 1 is a diagram showing a configuration of a microphone device in which two omnidirectional microphones according to an embodiment of the present invention are arranged in a straight line in a longitudinal direction so as to have directivity.

First, the configuration of the microphone device according to the present embodiment will be described with reference to FIG. In FIG. 1, reference numerals 21 and 22 are arranged in a straight line in the longitudinal direction, and the extension of the straight line is the direction of the talker so that directivity is given and the received air vibration is electroacoustic signal. (Hereafter, the omnidirectional microphones 21, 2
The first and second (reciprocally interchangeable) omnidirectional microphones, which are converted to and output as two output signals, 23 is a system in which the sound collection signal input from the omnidirectional microphone 21 is simply divided into two systems. It is a branching device that outputs.

Further, 24 is a low-pass filter for extracting only the low-frequency component in which the power of ambient noise such as wind noise is predominant in the sound collection signal input from one output of the branching device 23, 25
Is a sound pressure level calculator for calculating the sound pressure level of the low frequency component of the signal input from the omnidirectional microphone 21 input from the low pass filter, and 31 is the sound pressure level of the ambient noise from the sound pressure level calculator 25. Is compared with a predetermined level and is determined to be larger or smaller than that level, and the determination result is output to the switch 33.

Further, 26 is a second branching device which further divides the signal inputted from the other output of the branching device 23 into two systems and outputs it, and 27 is an omnidirectional input from one output of the second branching device 26. An amplifier that amplifies the signal from the directional microphone 21 and outputs the amplified signal to the switch 33, and 28 amplifies the signal from the omnidirectional microphone 21 input from the other output of the second branching device 26 and outputs the amplified signal to the adder 32. It is an amplifier that does.

Further, 29 is a phase inverter that inverts the phase of the input signal from the omnidirectional microphone 22 and outputs an antiphase signal, 30 is an amplifier that amplifies the antiphase signal from the phase inverter 29, and 32 is an amplifier 28. Omnidirectional microphone 2
1 output and omnidirectional microphone 22 from amplifier 30
And a non-directed signal from the amplifier 27, which is controlled by the determination result of the determiner 31 and which is added by the difference signal indicating the difference between the two input signals to the switch 33. The omnidirectional microphone 21 from the adder 32.
Of the output signal of the omnidirectional microphone 22 and the output signal of the omnidirectional microphone 22. The phase inverter 29 and the adder 3
And 2 constitutes a difference signal output means.

Next, the operation of the microphone device according to the present embodiment will be described in detail with reference to FIG.
First, the output signal (sound collection signal) from the omnidirectional microphone 21 is branched into two directions or two systems by the branching device 23,
One of the output signals is output to the low pass filter 24. The low-pass filter 24 extracts only the low-frequency component in which the power of ambient noise such as wind noise having high randomness is excellent from the input signal and outputs it to the sound pressure level calculator 25. The sound pressure level calculator 25 calculates the sound pressure level of the low frequency component and outputs the sound pressure level to the determiner 31, where the magnitude of the sound pressure level is determined and the determination result is output to the switch 33.

The output signal from the omnidirectional microphone 21 which is branched in the other direction by the branching device 23 is input to the second branching device 26, where it is branched into two systems again, one of which is amplified by the amplifier 27. And is output to one input terminal of the switch 33. The output signal from the other omnidirectional microphone 21 branched by the second branching device 26 is input to one input terminal of the adder 32 via the amplifier 28.

If the sound source is on the omnidirectional microphone 21 side on a straight line passing through the omnidirectional microphones 21 and 22, the omnidirectional microphone 22 is omnidirectional due to the delay converted from the air vibration and output. The electroacoustic signal (sound collection signal) whose phase is slightly delayed from the sound collection signal of the characteristic microphone 21 is inverted through the phase inverter 29, and is output as an anti-phase signal having a phase opposite to the output of the amplifier 28.
It is amplified by 0 and input to the other input terminal of the adder 32. The adder 32 outputs the outputs of the two amplifiers 28 and 30, that is, the sound collection signal of the omnidirectional microphone 21 and the opposite phase signal of the sound collection signal of the omnidirectional microphone 22 which is slightly behind the omnidirectional microphone 21 in phase. Is added to calculate the difference, and the difference signal due to the phase difference between the two signals is output to the switch 33.

The switch 33 receives the determination result from the determiner 31, selects either the output signal from the amplifier 27 or the output signal from the adder 32 according to the determination result, and outputs it to the speaker device. . That is, when the determiner 31 determines that the ambient noise such as wind noise having high randomness is high (large), the switcher 33 selects the output signal of the omnidirectional microphone 21 from the amplifier 27 and only that. When the ambient noise such as wind noise having high randomness is determined to be low (small), the switching unit 33 causes the omnidirectional output from the adder 32 to be omnidirectional. And outputs a signal composed of the difference between the output signal of the directional microphone 21 and the output signal of the omnidirectional microphone 22,
A strong directivity can be realized on the directional axis passing through the omnidirectional microphones 21 and 22 attached to the directional microphone device.

In the embodiment described above, the phase inverter and the adder are used as the difference signal output means, and
One of the signals picked up by the two omnidirectional microphones is made in opposite phase, and then added to the sound pickup signal of the other omnidirectional microphone to output the difference between the two sound pickup signals.
Instead of using the phase inverter and the adder, a differential amplifier may be used instead to output the difference between the sound collection signals of the two omnidirectional microphones.

Further, in the embodiment of the present invention described above, the case where two omnidirectional microphones are used has been described, but three or more omnidirectional microphones can be used. In the three cases, a combination of the first and second omnidirectional microphones and a combination of the first and second omnidirectional microphones can be used to realize a microphone with lower noise and stronger directivity. it can.

[0024]

The microphone device according to the present invention is configured as described above, and in particular, it determines the magnitude of the ambient noise amount in the low frequency band where the wind noise with high randomness is dominant,
If it is judged to be small, one of the signals picked up by the two omnidirectional microphones is reversed in phase according to the judgment result, and then the two picked up signals are added and output to switch the ambient noise. It is possible to exert strong directivity on a straight line that passes through two omnidirectional microphones while reducing the noise, and when wind noise with high randomness is determined to be large, the sound collection signals of the two omnidirectional microphones are determined. By adopting only one of them and automatically switching to output, it is possible to prevent an increase in the volume of ambient noise collected when wind noise with high randomness is large.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a microphone device including two omnidirectional microphones according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a microphone device including two conventional omnidirectional microphones.

[Explanation of symbols]

 21 omnidirectional microphone 22 omnidirectional microphone 23 branching device 24 low-pass filter 25 sound pressure level calculator 26 second branching device 27 amplifier 28 amplifier 29 phase inverter 30 amplifier 31 judging device 32 adder 33 switching device M1 Omnidirectional microphone M2 Omnidirectional microphone 101 Directional axis 102 Housing 103 Differential amplifier 104 Buffer amplifier 105 Speaker

Claims (3)

[Claims] 1. A first and a second omnidirectional microphones arranged in a straight line with a longitudinal direction thereof facing a speaker, and a low frequency component of an output signal collected by the first omnidirectional microphone. Of the sound pressure level of the first omnidirectional microphone and the phase difference between the output signal of the first omnidirectional microphone and the output signal of the second omnidirectional microphone, and the difference between them. A difference signal outputting means for outputting a signal and selecting and outputting only an output signal of the first omnidirectional microphone based on the judgment result of the judging means, or the first and second omnidirectional microphones. Switching means for switching between selecting and outputting a difference signal of the microphone output signals, and outputting only the output signal of the first omnidirectional microphone based on the determination result of the determining means. And the second nothing Microphone device being characterized in that to switch either automatically outputs a difference signal of the output signal of the tropism microphone. 2. The low-pass filter for extracting low-frequency components from the output signal collected by the first omnidirectional microphone, and the sound for calculating the sound pressure level of the extracted low-frequency components. A pressure level calculator, and compares the calculated sound pressure level with a predetermined level and outputs only the output signal of the first omnidirectional microphone to the switching means when the sound pressure level is higher. And when the sound pressure level is lower, a determiner that outputs a determination result instructing to output a difference signal due to the phase difference between the output signals of the first and second omnidirectional microphones. The microphone device according to claim 1, wherein: 3. A phase inverter for inverting the phase of the output signal collected by the second omnidirectional microphone to output a reverse phase signal, and the first omnidirectional microphone. From the adding means for adding the collected output signal and the inverted phase signal whose phase is inverted to output a difference signal due to the phase difference between the collected output signals of the first and second omnidirectional microphones. The microphone device according to claim 1 or 2, wherein: