JPH03219798A - Microphone equipment - Google Patents

Abstract

PURPOSE:To collect sound with excellent S/N by using a nondirective microphone and a unidirectional microphone as a set, eliminating a high frequency component from the output of the nondirective microphone, eliminating a low frequency component from the output of the unidirectional microphone and synthesizing both the resulting outputs. CONSTITUTION:A nondirective microphone 12 and a unidirectional microphone 13 are arranged so that the major axes are in parallel with each other opposite to a video integrated type camera main body 11. The output of the nondirective microphone 12 is given to a 2nd degree LPF and an output of the unidirectional microphone is given to an HPF. When the two microphones are of different polarity, the outputs are added and when of same polarity, the outputs are subtracted. Through the configuration above, noise, vibration and wind noise in the direction opposite to the major axis of the microphones are reduced and sound is collected with excellent S/N.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a microphone device that reduces noise, vibration, and wind noise in a direction opposite to the main axis of a microphone unit.

2. Description of the Related Art In recent years, integrated video cameras have become increasingly popular as devices that can easily record audio and video. Along with this, integrated video cameras have expanded in functionality and become smaller and lighter. Hereinafter, typical examples of conventional video integrated cameras will be described with reference to the drawings.

FIG. 7 shows the appearance of a conventional video integrated camera. In FIG. 7, 21 is a lens section, 22 is a microphone section, 23 is a viewfinder section, and 24 is a main body section. In order to avoid the effects of noise and vibration generated by the main body 24, the microphone unit 22 is fixed to the unit via a vibration-proofing material such as rubber, and is installed at a position away from the main body 24. Furthermore, a windshield is installed to reduce wind noise.

Problems to be Solved by the Invention However, when the video integrated camera is further miniaturized, the above-described configuration of the video integrated camera has problems both in terms of practicality and design.

On the other hand, as shown in FIG. 9, when the microphone unit 25 is embedded in the video integrated camera body, the microphone unit 25 is directly affected by the vibrations and noise generated by the main body 26. . Therefore, a problem arises in that the S/N ratio during sound collection is reduced, and the sound collection quality is significantly degraded. Possible countermeasures to this problem of low S/N ratio include using superdirectivity and using signal processing technology to remove noise, but these are difficult due to space constraints and cost. It is.

For the above reasons, a microphone device that is satisfactory in terms of performance, design, and cost has not yet been developed. The present invention provides a microphone device that uses an omnidirectional microphone and a unidirectional microphone to reduce noise, vibration, and wind noise in the direction opposite to the main axis of a microphone unit, and can collect sound with a good S/N ratio. The purpose is to

Means for Solving the Problems In order to achieve the above object, the microphone device of the present invention has an omnidirectional microphone unit and a unidirectional microphone unit arranged in parallel with their main axes facing opposite to the video integrated camera body. The output signal of the omnidirectional microphone unit is passed through a second-order low-pass filter, the output signal of the unidirectional microphone unit is passed through a second-order high-pass filter, and the output signal of the low-pass filter and the output signal of the high-pass filter are combined. are added when the two microphone units have different polarities, and are subtracted and output when the two microphone units have the same polarity.

Effects According to the present invention, with the above-described configuration, it is possible to reduce noise, vibration, and wind noise in the direction opposite to the main axis of the microphone unit, and it is possible to collect sound with a good S/N ratio.

The microphone device of the present invention uses a pair of omnidirectional microphone and unidirectional microphone units. High frequency components are removed from the output of the omnidirectional unit, low frequency components are removed from the output of the unidirectional unit, and a signal obtained by combining both is used as the output of the microphone device.

Embodiment First, the differences in the characteristics of omnidirectional microphones and unidirectional microphones with respect to sound, vibration, and wind noise will be explained.

First, let's talk about the sound. When using a microphone close to a sound source, if the sound source is a point source, the wavefront of the sound wave will be a spherical wave, and if a unidirectional microphone is used far from the sound source, the wavefront will be a plane wave. Sensitivity at 0 degrees and 180 degrees relative to the main axis of the unit is increased. Due to this proximity effect, a unidirectional microphone exhibits directional characteristics close to bidirectionality. On the other hand, in high frequency ranges, unidirectional microphones have low sensitivity to sounds in the opposite direction to the main axis of the unit due to their directivity, regardless of the distance from the sound source. In contrast, omnidirectional microphones exhibit flat frequency characteristics regardless of the distance from the sound source. Therefore, when there is a noise source in the opposite direction to the main axis of the unit, omnidirectional microphones are more effective against noise than unidirectional microphones in the low frequency range, and nondirectional microphones are more effective in reducing noise in the high frequency range. Unidirectional microphones are more advantageous in terms of noise than unidirectional microphones.

Next, let's talk about vibration. FIG. 8 shows the frequency characteristics of vibration sensitivity with respect to sound pressure sensitivity of an omnidirectional microphone and a unidirectional microphone. In FIG. 8, the solid line shows the frequency characteristics of the omnidirectional microphone, and the dotted line shows the frequency characteristics of the unidirectional microphone. As seen in FIG. 8, unidirectional microphones exhibit high sensitivity with respect to vibrations in the low frequency range, or fingerless microphones exhibit flat frequency characteristics with respect to vibrations. Therefore, omnidirectional microphones are more advantageous against vibrations than unidirectional microphones.

Next, let's talk about wind noise. The frequency components of wind noise are concentrated in a low frequency range, and omnidirectional microphones are generally less affected by wind noise than directional microphones. Therefore, omnidirectional microphones are more effective against wind noise than unidirectional microphones.

Hereinafter, a microphone device according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, an example will be described in which an omnidirectional microphone unit and a unidirectional microphone unit having mutually different polarities are used.

FIG. 1 shows the configuration of a microphone device according to an embodiment of the present invention, in which 11 is a video integrated camera body, 12 is an omnidirectional microphone unit, and 13 is a video integrated camera body.
14 is a unidirectional microphone unit, 14 is a second-order low-pass filter, 15 is a second-order high-pass filter, and 16 is an adder.

FIG. 2 shows the directional frequency characteristics of the unidirectional microphone when the sound source is far away, and FIG. 3 shows the directional frequency characteristics of the unidirectional microphone 13 when the sound source is nearby.

Solid lines in Figures 2 and 3.

The dashed line and the dashed-dotted line represent the sensitivity in directions of 0 degrees, 90 degrees, and 180 degrees with respect to the main axis of the microphone unit, respectively. The unidirectional microphone unit 13 has a sharp sensitivity in the low frequency range due to the proximity effect when the sound source is close as shown in Figure 3, compared to when the sound source is far away as shown in Figure 2. occurs. The cant-off frequencies of the low-pass filter 14 and the high-pass filter 15 are set to 1 to 2 KHz, which is the upper limit frequency at which the proximity effect appears.

FIG. 4 shows the transfer characteristics of filters 14 and 15 whose cutoff frequency is set to IKHz. In FIG. 4, the dotted line indicates the transfer characteristic of the low-pass filter 14, and the solid line indicates the transfer characteristic of the high-pass filter 15. The output signal of the omnidirectional microphone 12 passes through a low-pass filter 14, and the output signal of the unidirectional microphone unit 13 passes through a high-pass filter 15, and then the outputs of the filters 14 and 15 are added to obtain the output of the microphone device. .

FIG. 5 shows the directional frequency characteristics of the microphone device according to the present embodiment when the sound source is far away, and FIG. 6 shows the directional frequency characteristics of the microphone device according to the present embodiment when the sound source is nearby. In Figures 5 and 6, solid lines, broken lines, and dashed-dotted lines are 0 degrees and 90 degrees, respectively, relative to the front of the video body camera.
degree, represents the sensitivity in the 180 degree direction. As shown in FIGS. 5 and 6, the microphone device according to this embodiment synthesizes the low frequency component of the output of the omnidirectional microphone 12 and the high frequency component of the output of the unidirectional microphone 13 and outputs the synthesized result. do. Therefore, the effects of noise, vibration, and wind noise emitted by the video integrated camera body 11 can be reduced.

As described above, according to the microphone device of this embodiment,
It becomes possible to reduce noise, vibration, and wind noise in the direction opposite to the main axis of the microphone unit, and it is possible to realize sound collection with a good S/N ratio.

In addition, when using the omnidirectional microphone unit and the unidirectional microphone unit in this embodiment with the same polarity, by replacing the adder 16 in FIG. effect can be obtained.

Effects of the Invention As described above, the present invention provides an omnidirectional microphone unit and a unidirectional microphone unit having mutually different polarities.
The omnidirectional microphone unit outputs two
The output signal of the unidirectional microphone unit passes through the next low-pass filter, and the output signal passes through the second-order high-pass filter.
Add the output signal of a low-pass filter and the output signal of a high-pass filter, or use an omnidirectional microphone unit and a unidirectional microphone unit with the same polarity in parallel with their main axes facing opposite to the video integrated camera body. The output signal of the omnidirectional microphone unit passes through a second-order low-pass filter, the output signal of the unidirectional microphone unit passes through a second-order high-pass filter, and the output signal of the low-pass filter and the output of the high-pass filter are Since the configuration is such that signals are subtracted, it is possible to reduce the noise, vibration, and wind noise generated by the video integrated camera body, and it is possible to achieve sound collection with a good S/N ratio.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a microphone device according to an embodiment of the present invention, Fig. 2 is a directional frequency characteristic diagram of a unidirectional microphone when a sound source is far away, and Fig. 3 is a diagram of directional frequency characteristics when a sound source is nearby. A directional frequency characteristic diagram of a unidirectional microphone, FIG. 4 is a frequency characteristic diagram of a filter applied to this embodiment, and FIG. 5 is a directional frequency characteristic diagram of a microphone device in an embodiment of the present invention when a sound source is far away. Figure 6 is a directional frequency characteristic diagram of the microphone device in the embodiment of the present invention when there is a sound source nearby, Figure 7 is an external view of a conventional video integrated camera, and Figure 8 is an omnidirectional microphone and A frequency characteristic diagram of vibration sensitivity versus sound pressure sensitivity of a unidirectional microphone, and FIG. 9 is an external view of a video integrated camera with a built-in microphone in the main body. 11... Video integrated camera body, 12...
...Omnidirectional microphone unit, 13...
・Unidirectional microphone unit, 14...
Low pass filter, 15... High pass filter, 16... Adder.

Claims (2)

[Claims] (1) An omnidirectional microphone unit and a unidirectional microphone unit with opposite polarities are arranged in parallel with their main axes facing away from the video integrated camera body, and the output signal of the omnidirectional microphone unit is The output signal of the unidirectional microphone unit is passed through a second-order high-pass filter, and the output signal of the low-pass filter and the output signal of the high-pass filter are added and output. Microphone device. (2) Arrange an omnidirectional microphone unit and a unidirectional microphone unit of the same polarity in parallel with their main axes facing away from the video integrated camera body, and use the output signal of the omnidirectional microphone unit as a secondary A microphone characterized in that the output signal of the unidirectional microphone unit is passed through a second-order high-pass filter, and the output signal of the low-pass filter and the output signal of the high-pass filter are subtracted and output. Device.