JP2770593B2 - Microphone device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microphone device incorporated in a device having a noise source or a vibration source therein, and more particularly to a microphone device incorporated in a video integrated camera.

[0002]

2. Description of the Related Art Main factors that degrade the quality of sound pickup using a microphone include noise other than the intended sound, vibration noise due to mechanical vibration applied to the microphone, and wind noise. In particular, in the case of a device such as a video integrated camera, not only a mechanical system such as a tape drive unit inside the device generates noise and vibration, but also the device is frequently used outdoors.

FIG. 7 shows an example of a conventional stereo microphone for a video integrated camera. In FIG.
1, 72 are unidirectional microphone units. In such a microphone, two unidirectional units are arranged such that both main axes form a fixed opening angle, and the output of each unit is the output of the left and right two channels. When the microphone shown in FIG. 7 is incorporated in the main body, the distance between the microphone and these mechanical systems is reduced, and the absolute level of noise and vibration transmitted to the microphone is increased.

[0004]

In the case of a directional microphone, the proximity of a noise source to the microphone causes a proximity effect, and the sound pressure sensitivity in the front and rear directions increases in a low frequency range. It is more susceptible to the noise generated. Furthermore, directional microphones are more susceptible to vibration and wind than omnidirectional microphones.

Due to these factors, when a microphone having the configuration shown in FIG. 7 is used as a built-in type microphone, the S / N at the time of sound pickup is reduced, and the sound pickup quality is significantly deteriorated.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a built-in type microphone that can reduce noise and vibration generated by a mechanical system in a video-integrated camera main body and wind noise, and can collect sound with a high S / N. The purpose is to provide.

[0007]

In order to solve the above problems, the present invention uses three omnidirectional microphones to collect sound with low directivity in the low frequency range and directivity in the high frequency range. This is a stereo microphone that performs

[0008]

The microphone of the present invention is omnidirectional in the low frequency range and has low directivity in the direction of the noise source in the high frequency range. Therefore, wind noise and low-frequency vibration noise, whose frequency components are concentrated in the low frequency range, can be suppressed to the same level as the omnidirectional microphone, and the directivity of the high frequency range of the microphone depends on the distance between the noise source and the microphone. Since it is not affected, the effect of noise can be eliminated in high frequencies.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a microphone device according to a first embodiment of the present invention. In FIG. 1, reference numerals 11, 12, and 13 denote omnidirectional microphone units, and reference numerals 14 and 15 denote high-pass filters. , 16 are phase shifters, 1
Reference numerals 7 and 18 denote subtracters, and reference numerals 19 and 10 denote equalizers for correcting frequency characteristics. The unit 13 is disposed closer to the video camera body than the other two units, and the units 11 and 13 constitute a right channel, and the units 12 and 13 constitute a left channel.

The operation in the right channel will be described below. The low-frequency component of the output signal of the unit 11 is removed by the high-pass filter 14. The phase of the output signal of the unit 13 is delayed by the phase shifter 16. The output signal of the phase shifter 16 is added to the output signal of the high-pass filter 14 in reverse phase, and the frequency characteristic is corrected by the equalizer 19 and output.

First, the operation of the microphone device of the present embodiment in a high frequency range equal to or higher than the cutoff frequency of the high-pass filter 14 will be described. In the microphone device of the present embodiment, the two omnidirectional microphone units 1 are connected to the output of the omnidirectional microphone unit 13 by the phase shifter 16.
By giving a phase delay according to the interval between 1 and 13 and adding an opposite phase to the output of the omnidirectional unit 11 that has passed through the high-pass filter 14, a primary sound pressure gradient type microphone is obtained in this frequency band. Directivity D at this time
Is a function of the angle θ between the main axis of the microphone device and the direction in which the sound wave arrives,

[0013]

(Equation 1)

Is given by In Equation (1), α is a constant determined by the time constant τ of the phase shifter 16, and α and τ
The relationship is that the interval between the microphone units is d, and the sound speed is c.
As

[0015]

(Equation 2)

Can be expressed as The directivity is bidirectional when α = 0, unidirectional when α = 1, and omnidirectional when α = ∞. Therefore, the time constant of the phase shifter 16 is set such that a directional pattern with low sensitivity in the direction of the noise source is obtained. That is, by adjusting the time constant, the directivity pattern in the high frequency range can be changed according to the direction of the noise source.

On the other hand, in the low frequency range below the cutoff frequency of the high-pass filter 13, the output of the subtracter 17 is almost the output of the phase shifter 16, so that the directivity of the microphone device of the present embodiment is non-directional. And sex.

FIG. 2 shows an example of the directional frequency characteristic of the right channel output of the microphone device of the present embodiment before passing through the equalizer 19. In the figure, the vertical axis is a relative value based on the sound pressure sensitivity of the omnidirectional microphone unit. FIG. 3 shows an example of a high-frequency directivity pattern of the right channel output of the microphone device of the present embodiment.
In FIG. 3, N is a noise source.

As described above, the directivity of the microphone device according to the present embodiment is non-directional in a low frequency range, and low in a direction of a noise source in a high frequency range. Therefore,
The wind noise and the low frequency vibration noise whose frequency components are concentrated in the low frequency can be suppressed to the same level as the omnidirectional microphone, and the directivity of the high frequency of the microphone is not affected by the distance between the noise source and the microphone. Therefore, the effect of noise can be eliminated in a high frequency range. Although the low frequency band is omnidirectional, the cutoff frequency of the high-pass filter is set to 200.
If the frequency is set in the range from Hz to 300 Hz, a stereo feeling without practical problems can be obtained. The same applies to the left channel.

FIG. 4 shows a configuration of a microphone device according to a second embodiment of the present invention. In FIG. 4, reference numerals 41, 42, and 43 denote omnidirectional microphone units, and reference numerals 44 and 45 denote high-pass filters. , 46 are phase shifters, 4
7 and 48 are subtracters, 49 and 40 are equalizers for correcting frequency characteristics, and 50 is a fixture. The difference from the first embodiment is that three units are arranged so that their main axes are parallel and in the same direction, and when vibration is applied to the three units, all units vibrate integrally. It is fixed. With such a configuration, since the vibration is transmitted to both units with the same amplitude and the same phase, the high-frequency vibration sensitivity of the microphone device of the present embodiment is set to be 90 ° with respect to the main axes of the microphones of the left and right channels. It shows characteristics equal to the sound pressure sensitivity when a sound wave arrives.

FIG. 5 shows an example of the directional frequency characteristic of the right channel output of the microphone device of the present embodiment before passing through the equalizer 49. In the figure, the vertical axis is a relative value based on the sound pressure sensitivity of the omnidirectional microphone unit. As described above, in the band equal to or higher than the cutoff frequency of the high-pass filters 44 and 45, the vibration sensitivity of the microphone device of the present embodiment is lower than the vibration sensitivity of the non-directional microphone unit. The vibration sensitivity decreases as the value of α in (Equation 2) decreases. Other operations are the same as in the first embodiment.

FIG. 6 shows the configuration of a microphone device according to a third embodiment of the present invention. In FIG. 6, reference numerals 61, 62 and 63 denote omnidirectional microphone units, and reference numerals 64 and 65 denote phase shifters. , 66 is a high-pass filter, 6
7 and 68 are subtracters, and 69 and 60 are equalizers for correcting frequency characteristics. The difference from the first embodiment is that
A unit 63 is arranged on the front side of the video camera with respect to the other two units, and a left channel is constituted by 61 and 63, and a right channel is constituted by units 62 and 63. Independent phase shifters are constituted by left and right channels. Is to have.

Therefore, by setting α in (Equation 2) to a different value between the two channels, it is possible to realize different high-frequency directivities on the left and right. That is, even when the direction of the noise source affecting each of the left and right channels is different, or when the apparent direction of the noise source is different due to reflection and diffraction by the housing of the device containing the microphone, the respective left and right channels are independent. It is possible to realize directivity such that sensitivity decreases in the direction of the noise source. Other operations are the same as in the first embodiment.

[0024]

As described above, according to the present invention, three omnidirectional microphone units are used to collect sound with low directivity in a low frequency range and low sensitivity in the direction of a noise source in a high frequency range. By doing so, the wind noise and low-frequency vibration noise can be suppressed to the same level as the omnidirectional microphone, and at the same time, the effect of noise can be eliminated in the high frequency range. Furthermore, by arranging the units so that the principal axes of the microphone units are parallel and in the same direction, and fixing all the units so that they vibrate together, the vibration sensitivity in the high frequency range is reduced by the omnidirectional microphone. It is lower than the vibration sensitivity of the unit. Therefore, by mounting the microphone device of the present invention on a video integrated camera,
It is possible to prevent a decrease in S / N during sound pickup.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a directional frequency characteristic of the microphone device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of a high-frequency directional characteristic of the microphone device according to the first embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 5 is a diagram illustrating an example of a vibration sensitivity frequency characteristic of the microphone device according to the second embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 7 is a diagram illustrating an example of a configuration of a conventional stereo microphone.

[Description of Signs] 10, 19, 40, 49, 60, 69 Equalizer 11, 12, 13 Non-directional microphone unit 14, 15 High-pass filter 16 Phase shifter 17, 18 Subtractor 41, 42, 43 Non-directional microphone Units 44, 45 High-pass filter 46 Phase shifter 47, 48 Subtractor 49, 60 Equalizer 50 Fixture 61, 62, 63 Non-directional microphone unit 64, 65 Phase shifter 66 High-pass filter 67, 68 Subtractor 69 Equalizer

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hiroshi Kobayashi 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-62-95097 (JP, A) JP-A-4-192796 (JP, A) JP-A-63-232700 (JP, A) Jpn. ) Actually open 3-90594 (JP, U)

Claims (3)

(57) [Claims] A first and a second omnidirectional microphones arranged on a straight line at an interval from each other and a vertical bisector of a line connecting the first and the second omnidirectional microphones. A third omnidirectional microphone disposed therein;
A first high-pass filter for removing a low-frequency component of an output signal of the omnidirectional microphone, and a second high-pass filter for removing a low-frequency component of an output signal of the second omnidirectional microphone.
A high-pass filter, a phase shifter for delaying the phase of the output signal of the third omnidirectional microphone, and a first subtraction for mixing the output of the phase shifter with the output of the first high-pass filter in reverse phase. And a second subtractor for mixing the output of the phase shifter with the output of the second high-pass filter in reverse phase. 2. The three omnidirectional microphones according to claim 1, wherein the main axes of the three omnidirectional microphones are arranged in parallel and in the same direction, and the three omnidirectional microphones are fixed so as to vibrate integrally. Microphone device. 3. A vertical bisector of a line connecting the first and second omnidirectional microphones and the first and second omnidirectional microphones arranged on a straight line at an interval from each other. A third omnidirectional microphone disposed therein;
A first phase shifter for delaying the phase of the output signal of the omnidirectional microphone, a second phase shifter for delaying the phase of the output signal of the second omnidirectional microphone, and the third omnidirectional A high-pass filter that removes a low-frequency component of the output signal of the microphone; a first subtractor that mixes the output of the high-pass filter with the output of the first phase shifter in reverse phase; A microphone device comprising: a second subtractor that mixes an output of a second phase shifter in a reverse phase.