JPH057392A - Microphone device - Google Patents

Abstract

PURPOSE:To reduce wind noise regardless of the quantity of an energy of a sound signal by extracting a low frequency component of a signal component without correlation from the sound signal from one or plural microphone units and reducing the low frequency component in response to the detection output. CONSTITUTION:A signal component without correlation is extracted by an adder 230 from a sound signal from microphone units 10,20 and an LPF 240 extracts further the low frequency component. Then an attenuation ratio of variable attenuators 170,180; 190,200 is subject to variable control in response to a level detected and outputted from a peak detection circuit 250. Thus, even when the energy of a low frequency component of a real sound is high, the wind noise is eliminated without elimination of the low frequency component of the real sound by attenuating the attenuation in response to the quantity of a wind noise level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microphone device which comprises a plurality of microphone units, and obtains an output audio signal based on each audio signal from the plurality of microphone units.

[0002]

2. Description of the Related Art When a voice is picked up in stereo, basically, two unidirectional microphones 300 are prepared, and each microphone 3 is, as understood from FIG.
00, the sound receiving directions are at an angle θ (= 90 ° to 1) with respect to each other.
30 °) and the sound receiving position has a value of 15 cm
It is arranged at the above position.

A unidirectional microphone 300 generally has a directional characteristic shown by a curve P in FIG. 10, and the curve P is obtained when the microphone 300 is arranged at the center O. ..

Further, as understood from FIG. 9, when the microphone 300 is used while being mounted in the microphone capsule 300A, the sound waves A and B of the sound source received from the front surface and the back surface of the microphone capsule 300A. The directivity of FIG. 10 is obtained when is combined.

Therefore, a space without obstacles (reflection surface) is secured on the back side of the microphone capsule 300A so that the sound wave of the sound source is not reflected (sound wave C) and received by the microphone 300. There is a need to.

[0006]

However, for example, in a small-sized video camera, when the unidirectional microphone 300 is built in the casing of the video camera, a sufficient space cannot be secured around the microphone capsule 300A. Since stereo recording cannot be performed, for example, a one-point stereo microphone is provided so as to project outside the casing.

Therefore, there is a demand for the development of a microphone that can be built in the casing and can collect sound in stereo because the video camera is downsized and the degree of freedom in design is limited.

Therefore, the applicant of the present invention has previously filed Japanese Patent Application No. 2-1.
No. 32051 (filing date: May 22, 1990), for example, proposed a built-in stereo microphone device in which audio is picked up by a stereo in a state of being built in a casing of a video camera.

This built-in type stereo microphone device is
A box-shaped cabinet provided with a space in which two omnidirectional microphone units for both the left and right channels can be arranged at a desired distance, and one of the two microphone units A delay circuit for delaying an audio signal output from the microphone unit by a time corresponding to the distance between the two microphone units;
One of the microphone units has an adder that weights the audio signal output from the other microphone unit by inverting the polarity of the audio signal delayed by the delay circuit.

The built-in type stereo microphone device of the prior art will be described below with reference to the drawings. As can be understood from FIGS. 4 and 5, the stereo microphone device 1 is
It has a cabinet 3 having a substantially convex cross section, and two microphone units 10 and 20 for the left and right (L, R) channels provided in the cabinet 3.

The cabinet 3 is provided with a space 3a in which the sound receiving surfaces c and d of the two microphone units 10 and 20 are separated by a distance (W; for example, a value of 30 cm).

In addition, each microphone unit 10, 2
For example, 0 is omnidirectional having a directional characteristic shown by a curve Q in FIG. 6, and the sound receiving surfaces c and d are in the posture toward the outer surface of the cabinet 3 and the sound receiving Protective net materials 5 and 5 are fixed to the cabinet 3 in front of the surfaces c and d.

As understood from FIG. 3, the sound waves received by the left and right microphone units 10 and 20 are converted into audio signals, and the buffer amplifiers 30 and 4 respectively.
It is input to the delay circuits 50 and 60 via 0, and is input to the adders 100 and 90 via the attenuators 70 and 80, respectively. In this case, the polarities of the output signals of the attenuators 70 and 80 are inverted, and the output signals of the buffer amplifiers 40 and 30 are also input to the adders 100 and 90, respectively. Then, the output signals of the adders 90 and 100 are respectively passed through equalizers (equalizers) 110 and 120 to L
It is output to the output terminals 130 and 140 as output audio signals of the channel and the R channel.

It is preferable that the delay circuits 50 and 60 use general low-pass filters mainly composed of resistors and capacitors.

In the stereo microphone device 1 configured as described above, a sound wave having a wavelength shorter than the distance W (for example, a sound wave having a frequency of 6 [kHz] or more) is tuned to the microphone unit 10 as understood from FIG. (Or 20)
There is a level difference corresponding to the distance W between the audio signals α, β, γ that are collected and output from the front, back, and front of the
Due to such frequency characteristics, a stereo effect can be obtained.
That is, with respect to sound waves having a frequency of 6 [kHz] or higher, stereo sound is picked up by the structure of the cabinet 3.

On the other hand, for a sound wave having a frequency lower than 6 [kHz], the circuit configuration shown in FIG.
A stereo feeling is realized. That is, as shown in FIG. 5, when the R channel microphone unit 20 is closer to the sound source A and the sound source B, the time when the sound wave reaches the L channel microphone unit 10 is Distance A to A (distance between c and d), sound source B
On the other hand, during the distance X (distance between e and d), the arrival at the microphone unit 20 is delayed by the amount of time the sound wave travels. Therefore, the output signal of the buffer amplifier 40 is delayed by the delay circuit 60 by the delayed time, and the delayed signal is subtracted from the output signal of the buffer amplifier 30, so that the output of the adder 90 is substantially offset. As a result, a stereo feeling can be obtained. If the sound source is close to the microphone unit 10, on the contrary, R
Channel outputs are canceled.

Explaining the above principle in detail, the sound wave arriving at the microphone unit 20 is now represented by sin ωt (ω
Is an angular velocity; t is a time), a sound wave received by the microphone unit 10 is L (ω), a delay phase angle φ (a function of W and ω) in the microphone unit 10, and a change amount of the attenuator 80 is a (≦ 1) If the phase angle that reaches the delay amount of the delay circuit is ψ, the following equation (1) is given.

L (ω) = sin (ωt−φ) −asin (ωt−ψ) = asinωt · cosφ−cosωt · sinφ−a (sinωt · cosψ−cosωt · sinψ) = sinωt · cosφ−asinωt · cosψ−cosωt -Sin (phi) + a cos (omega) t * sin (psi) = (sin (omega) t) (cos (phi) -cos (psi))-(cos (phi) -sin (psi)) + (1-a) (sin (omega) t * cos (psi) -cos (omega) * sin (psi)) = (sin (omega) t) = 2sin ((phi + phi)) / 2). -Sin (φ-φ) / 2}-(cosωt)-{2cos (φ + φ) / 2-sin (φ-φ) / 2} + (1-a) sin (ωt-φ) = {2sin (φ-) φ) / 2} · {sin ωt · sin (φ + φ) / 2 −cosωt · cos (φ + φ) / 2} + (1-a) sin (ωt−ψ) = − {2sin (Φ−φ) / 2} · cos {ωt + (φ + φ) / 2} + (1-a) sin (ωt−ψ) ··· (1)

Therefore, when the delay amount is set to be equal to the delay phase angle, φ = φ, and therefore, from the above equation (1), L (ω) = (1-a) sin (ωt−φ) Further, if a = 1 is set, then L (ω) = 0. In this case, the sound wave R (ω) received by the microphone 20 is represented by the following expression (2). R (ω) = sin ωt−asin (ωt−φ−ψ) (2) Therefore, if the above equation (2) is transformed, R (ω) = sin ωt {1-cos (φ + ψ)} + cosωt · sin ( φ + ψ) + (1-a) sin (ωt−φ−ψ) (3) Therefore, if φ = ψ, R (ω) = 2sinφ · cos (ωt−φ) + (1-
a) sin (ωt-2φ). Here, if a = 1, then R (ω) = 2cos (ωt−φ) · sinφ. According to the above equations (1) and (3), i) When the sound source is at a position where φ = ψ, R (ω) = 2sinφ · cos (ωt−φ) + (1-a) sin (ωt−2φ) L (ω) = (1-a) sin (ωt−ψ) ii) φ = ψ and a = 1 R (ω) = 2 sin φ · cos (ωt−φ) L (ω) = 0 iii) φ When ≠ ψ and a = 1, R (ω) = sin ωt {1-cos (φ + · ψ)} + cosωt · sin (φ + ψ) L (ω) = {2sin (φ−ψ) / 2} cos {ωt + ( φ + ψ) / 2}, and in each case, as can be understood from the frequency characteristics of FIG. 7, a stereo feeling (level difference between left and right) can be obtained.

As described above, in this prior art example, 6
For sound waves having frequency characteristics of [kHz] or higher,
The structure of the cabinet 3 gives a stereo feeling,
For sound waves having a frequency lower than [kHz],
The electrical processing gives a stereo effect. Since the cabinet 3 is integrated with the casing of the video camera 200, the stereo microphone device 1 can collect sound by stereo while the stereo microphone device 1 is built in the casing of the video camera 200.
The video camera 200 can be built in and miniaturized.
In addition to further miniaturization, the degree of freedom in design such as the overall design is improved.

As can be understood from the above description, in the built-in stereo microphone device of this prior art example, the cabinet structure gives a stereo feeling to relatively high-pitched sound and relatively low-pitched sound. For
With an electrical component mainly composed of a delay circuit and an adder,
It gives a sense of stereo. Therefore, even when the cabinet is integrated with the casing of the video camera, that is, even when the microphone is built in the casing, the sound can be picked up in stereo. Therefore,
In addition to downsizing the microphone device, the degree of freedom in designing, for example, a video camera is improved, and
Further downsizing is possible.

By the way, as a method of reducing wind noise, attention has been paid to the fact that this wind noise is 1 / f noise, and when the volume of the low frequency becomes large, the low frequency is automatically reduced. Therefore, a method for reducing wind noise has been proposed.
However, this conventional method has a drawback that the low range of the real sound is attenuated because it works even when the energy of the low range of the real sound is large.

In view of the above point, the present invention provides a microphone device which includes a plurality of microphone units and obtains an output audio signal based on each audio signal from the plurality of microphone units. The wind noise in the sound signal of the above can be reliably reduced regardless of the energy of the sound signal.

[0024]

A microphone device according to the present invention comprises a plurality of microphone units 10 and 20, and obtains an output sound signal based on each sound signal from the plurality of microphone units 10 and 20. In the microphone device described above, low-frequency mitigation circuits 150, 170, 180, 210; 16 to which output audio signals are supplied.
0, 190, 200, 220 and extraction circuits 230, 240 for extracting low-frequency components of uncorrelated signal components from the audio signals from the plurality of microphone units 10, 20.
And a detection circuit 250 for peak-detecting low-frequency components of uncorrelated signal components from the extraction circuits 230 and 240, and low-frequency mitigation circuits 150 and 170 according to the detection output from the detection circuit 250. 180, 210; 160,
The degree of low-frequency reduction of 190, 200, 220 is controlled.

[0025]

According to the present invention, the low-frequency mitigating circuits 150, 170, 180, 210; 1 are controlled by the detection output from the detecting circuit 250 so that the more wind noise is suppressed, the more it is suppressed.
It controls the degree of low frequency reduction of 60, 190, 200, 220.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a stereo microphone device of the prior art will be described below with reference to FIG. In addition, in FIG. 1, portions corresponding to those in FIG.

A low-frequency reducing circuit is provided on the output side of the equalizing circuit 110. That is, the high-pass filter 150, the variable attenuators 170 and 180 to which the output of the equalization circuit 110 is directly supplied through the high-pass filter 150, and the variable attenuators 170 and 18 are provided to the output side of the equalization circuit 110.
A low-frequency reducing circuit including an adder 210 to which each output of 0 is added is provided, and an output terminal 130 is derived from the adder 210.

A low-frequency reducing circuit is provided on the output side of the equalizing circuit 120. That is, the high-pass filter 160, the variable attenuator 190, 200 to which the output of the equalizer circuit 120 is directly supplied through the high-pass filter 160, and the variable attenuator 190, 20 are provided to the output side of the equalizer circuit 120.
A low-frequency reducing circuit including an adder 220 to which each output of 0 is added is provided, and an output terminal 140 is derived from the adder 220.

When the distance between the left and right microphone units 10 and 20 is relatively small, the actual sound signals in each audio signal have a strong correlation, but the high frequencies thereof have a weak correlation. Also, the level of the high frequency component of the wind noise signal in each audio signal is considerably low. Therefore, the left and right microphone units 10, 2
By supplying each audio signal from 0 to the adder 230 and subtracting the other from one, the uncorrelated signal component is extracted, and the uncorrelated signal component is supplied to the low-pass filter 240. , The low-frequency component is extracted, that is, the high-frequency component is blocked, and the low-frequency component of the uncorrelated signal component is supplied to the peak detection (detection) circuit 250 for peak detection (detection), and its detection. The damping ratio of the variable attenuators 170, 180; 190, 200 is variably controlled according to the output level.

Next, the operation of this embodiment will be described. The higher the level of the wind noise signal in each audio signal from the microphone units 10 and 20, the higher the peak detection (detection) circuit 25.
As the level of the detection output of 0 increases and the level of the wind noise signal in each audio signal from the microphone units 10 and 20 decreases, the level of the detection output of the peak detection (detection) circuit 250 decreases. Therefore, as the level of the detection output of the peak detection (detection) circuit 250 is increased, the attenuation amounts of the variable attenuators 170 and 190 are increased, the attenuation amounts of the variable attenuators 180 and 200 are decreased, and the peak detection ( The smaller the level of the detection output of the detection circuit 250, the smaller the attenuation amount of the variable attenuators 170 and 190 and the larger the attenuators of the variable attenuators 180 and 200. Thus, the wind noise signal in the audio signals from the microphone units 10 and 20 is reliably removed, and even if the energy of the low frequency component of the actual sound signal is large, the low frequency component of the actual sound signal is removed. There is no danger of Therefore, in the above-mentioned stereo microphone device, the effect of removing wind noise is great.

As shown in FIG. 2, a microphone device (stereo microphone device) 1 is, for example, a video camera 2.
00 is integrally provided on the front surface of the casing.
Note that other configurations are the same as those in FIGS. 3 to 7 and the description thereof in the above-described prior art example, and thus redundant description will be omitted.

[0032]

According to the present invention described above, a plurality of microphone units are provided, and an output audio signal is obtained based on each audio signal from the plurality of microphone units. It is possible to obtain the wind noise in the audio signal of the audio signal from the device which can surely be reduced regardless of the energy level of the audio signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a perspective view showing an embodiment in which a microphone device is attached to a video camera.

FIG. 3 is a block diagram showing a preceding example.

FIG. 4 is a schematic diagram showing a configuration of a cabinet of a prior example.

FIG. 5 is an explanatory diagram showing a positional relationship between a microphone unit and a sound source of a prior art example.

FIG. 6 is a diagram showing the directional characteristics of the omnidirectional microphone unit of the preceding example.

FIG. 7 is a curve diagram showing frequency characteristics of a microphone unit.

FIG. 8 is an explanatory diagram of conventional stereo recording.

FIG. 9 is a diagram showing a usage pattern of a conventional unidirectional microphone device.

FIG. 10 is a curve diagram showing directional characteristics of a conventional unidirectional microphone unit.

[Explanation of symbols]

 10 microphone capsule 20 microphone capsule 30 amplifier 40 amplifier 50 delay device 60 delay device 70 attenuator 80 attenuator 90 adder 100 adder 110 equalizer 120 equalizer 150 high-pass filter 160 high-pass filter 170 attenuator 180 attenuator 190 attenuation 200 attenuator 210 adder 220 adder

Claims (1)

Claim: What is claimed is: 1. A microphone device comprising a plurality of microphone units, wherein an output audio signal is obtained based on each audio signal from the plurality of microphone units. A low-frequency reduction circuit, an extraction circuit for extracting low-frequency components of uncorrelated signal components from each of the audio signals from the plurality of microphone units, and a low-correlation signal component reduction circuit for extracting low-frequency components of the uncorrelated signals. A microphone device having a detection circuit for peak detection of a range component, and controlling the degree of low range reduction of the low range reduction circuit by a detection output from the detection circuit.