JP2770594B2 - 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 inside the device generates noise and vibration, but also the device is frequently used outdoors.

Conventionally, in such a device, the distance between the microphone and these mechanical systems is reduced by incorporating the microphone in the main body. However, if such a device is integrally configured, noise transmitted to the microphone is reduced. And the absolute level of vibration increases.

[0004]

In general, when the positional relationship between a microphone and a noise source is fixed, the influence of noise can be eliminated by a suitable directional microphone. However, in the case of a directional microphone, a proximity effect occurs when the noise source approaches the microphone,
In the low frequency range, the sound pressure sensitivity in the front and rear directions increases, and consequently, it is more susceptible to the noise generated by the equipment, and S / S
N decreases. Furthermore, directional microphones are more susceptible to vibration and wind than omnidirectional microphones.

[0005] Due to these factors, when a directional microphone 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 two omnidirectional microphones to collect sound with low directivity in the low frequency range and directivity in the high frequency range. Is what you do.

[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 and 12 denote omnidirectional microphone units.
3 is a high-pass filter, 14 is a phase shifter, 15 is a subtractor,
Reference numeral 16 denotes an equalizer for correcting frequency characteristics.
The low frequency component of the output signal of the unit 11 is removed by the high-pass filter 13, and the phase of the output signal of the unit 12 is delayed by the phase shifter 14. High Pass High Pass 1
The output signal of the phase shifter 14 is added to the output signal of No. 3 in reverse phase, and the equalizer 16 corrects the frequency characteristic and outputs the corrected signal.

First, the operation of the microphone device according to the present embodiment in a high frequency range equal to or higher than the cutoff frequency of the high-pass filter 13 will be described. In the microphone device of the present embodiment, the output of the omnidirectional microphone unit 12 is subjected to a phase delay according to the interval between the two units 11 and 12 by the phase shifter 14, and this signal is passed through the high-pass filter 13.
Is added to the output of the omnidirectional microphone unit 11 that has passed through the phase shifter, thereby providing a primary sound pressure gradient type microphone in this frequency band. The directivity D at this time is expressed as a function of the angle θ between the main axis of the microphone device and the direction in which the sound wave arrives.

[0012]

(Equation 1)

[0013] In Equation (1), α is a constant determined by the time constant τ of the phase shifter 14, and α and τ
The relationship is that the interval between the microphone units is d, and the sound speed is c.
As

[0014]

(Equation 2)

It 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 14 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 15 is almost the output of the phase shifter 14, so that the directivity of the microphone device of the present embodiment is omnidirectional. And sex.

FIG. 2 shows an example of the directional frequency characteristic of the microphone device of the present embodiment before passing through the equalizer 16. The vertical axis in the figure 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 microphone device according to the present embodiment. In FIG. 3, N is a noise source. As described above, the directivity of the microphone device of the present embodiment is omnidirectional in a low frequency range, and low in a direction of a noise source in a 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.

FIG. 4 shows a configuration of a microphone device according to a second embodiment of the present invention. In FIG. 4, reference numerals 41 and 42 denote omnidirectional microphone units,
3 is a high-pass filter, 44 is a phase shifter, 45 is a subtractor,
46 is an equalizer, and 47 is a fixture. The difference from the first embodiment is that the two units 41 and 42 are fixed so that the principal axes of the two units 41 and 42 coincide with each other, and when vibration is applied to the two units, both units vibrate integrally. It is that you are. With this configuration, the vibration is transmitted to both units at the same amplitude and in the same phase. Shows the same characteristics as the sound pressure sensitivity in the case where. (Fig. 5) with equalizer 4
6 shows an example of the vibration sensitivity frequency characteristic of the microphone device of the present embodiment before passing through 6. The vertical axis in the figure is a relative value based on the vibration sensitivity of the omnidirectional microphone unit.
As described above, in the band equal to or higher than the cutoff frequency of the high-pass filter 43, the vibration sensitivity of the microphone device of the present embodiment is lower than the vibration sensitivity of the omnidirectional microphone unit. The vibration sensitivity decreases as the value of α in (Equation 2) decreases. For other operations,
This is the same as the embodiment.

[0019]

As described above, according to the present invention, two 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 main axes of the microphone units are aligned and in the same direction, and fixing the two units so that they vibrate together, the vibration sensitivity in the high frequency range is omnidirectional. Lower than the sensitivity of the vibration microphone 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.

[Explanation of symbols]

11, 12, 41, 42 Non-directional microphone unit 13, 43 High-pass filter 14, 44 Phase shifter 15, 45 Subtractor 16, 46 Equalizer 47 Fixture N Noise source

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroshi Kobayashi 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-60-198993 (JP, A) JP-A-56-89194 (JP, A) JP-A-56-50697 (JP, A) Jpn. ) Japanese Utility Model Showa 56-56289 (JP, U) Japanese Utility Model Showa 56-31789 (JP, U)

Claims (2)

(57) [Claims] 1. A first and second omnidirectional microphones arranged on a straight line at an interval from each other, a high-pass filter for removing a low-frequency component of an output signal of the first omnidirectional microphone, A microphone comprising: a phase shifter that delays the phase of an output signal of the second omnidirectional microphone; and a subtractor that mixes the output of the high-pass filter with the output of the phase shifter in reverse phase. apparatus. 2. The two omnidirectional microphones are arranged such that their main axes are aligned and oriented in the same direction.
2. The microphone device according to claim 1, wherein the two omnidirectional microphones are fixed so as to vibrate integrally.