JPH0564289A - Microphone unit - Google Patents

Abstract

PURPOSE:To provide the microphone unit which can collect sounds while being interlocked with a zooming mechanism such as a video camera or the like and can be built in while improving noise the resistance of noise such as vibrations, adjacent noise or wind. CONSTITUTION:While using three non-directional microphones 1-3, first and second subtracters 7 and 8 subtract outputs from the third non-directional microphone 3 through a delay equipment 6 from outputs from the first and second non-directional microphones 1 and 2 through first and second high-pass filters 4 and 5, and the outputs of the first and second subtracters 7 and 8 are respectively mixed by first and second variable mixers 9 and 10 according to the control signal of a controller 11.

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 picking up sound according to an image by interlocking with a zooming mechanism such as a video camera or an 8 mm camera, and more particularly to a device having a noise source or a vibration source inside. Relates to a microphone device built in.

[0002]

2. Description of the Related Art In recent years, in order to integrate video and audio for video integrated cameras and 8 mm cameras,
A microphone device capable of collecting a zoom sound in synchronization with an image has been developed. There are two types of these conventional microphone devices, a monaural type and a stereo type.

The former monophonic microphone device changes the sound collection angle of the microphone in accordance with the angle of view of the camera, and is based on the technique of varying the directional pattern, and usually comprises a plurality of microphones. It is realized by synthesizing the output of the directional microphone. In addition, in order to enhance the zoom effect, a method of increasing the sensitivity from a wide angle to a telephoto is generally adopted (for example, Japanese Patent Publication No. 59-101).
19). In order to obtain an excellent zoom effect, it is necessary to match the angle of view with the angle of sound collection. An example of the angle of view of the 10 × zoom lens is about 40 degrees at wide angle and about 4 degrees at telephoto. On the other hand, the sound collecting angle of the microphone is about 100 degrees at most even in the secondary sound pressure gradient type which is currently put into practical use as the sharp directivity, which is too wide as compared with the view angle of the zoom lens. Therefore, there was no expected effect.

The latter stereo type microphone device audibly corrects the drawbacks of the above monaural type microphone device and produces a natural zoom effect by adding information on the movement and direction of the subject. Is. It changes the sound collection angle of the left and right channels, the directivity main axis, and the sensitivity according to the angle of view of the camera, and mainly focuses on stereo sound collection with a wide sense of presence when wide angle, and clearly collects the target sound source when telephoto. Directional sound collection is the main subject. Similar to the monaural type microphone device, this microphone device is usually realized by combining the outputs of a plurality of directional microphones (for example, Japanese Patent Publication No. 60-24636).

[0005]

However, since the conventional microphone device as described above uses a directional microphone such as unidirectional or bidirectional, as shown below, a video integrated camera is used. There was a problem in incorporating it into such devices.

Microphones are roughly classified into omnidirectional microphones and directional microphones, each having the following characteristics. An omnidirectional microphone has uniform sound pressure sensitivity frequency characteristics that do not depend on the direction, distance, and frequency of the sound source, and vibration sensitivity frequency characteristics that do not depend on frequency. On the other hand, in the directional microphone, the sound pressure sensitivity changes not only with the direction of the sound source but also with the distance. That is, when the distance between the sound source and the microphone becomes short, the sensitivity in the front direction and the back direction increases in the low sound range due to the so-called proximity effect. Further, its vibration characteristic also becomes high in the low frequency range. further,
Similarly, the sensitivity in the low frequency range becomes high with respect to wind.

From the above, in a sound collecting environment in which ambient noise does not exist, it is generally advantageous that the microphone has a sharp directivity. However, if the distance between the sound source and the microphone becomes short, it is necessary to correct the proximity effect. next,
In a sound collecting environment in which a noise source exists near the microphone, for example, a microphone built into a video-integrated camera has a noise source and a vibration source such as a drive system of a zoom lens and a tape running system. In such an environment and when the components of these noise sources are concentrated in the low frequency range, the omnidirectional microphone is more advantageous than the directional microphone. On the contrary, when the noise source components are concentrated in the high range,
Directional microphones have advantages over omnidirectional microphones. However, when wind is present due to outdoor use, the omnidirectional microphone is advantageous at least in the low frequency range.

[0008] As described above, in the case where a device such as a video-integrated camera has a vibration source or a noise source inside and is also used outdoors, it has a directional microphone as a constituent element. However, the microphone device has a problem that the SN ratio of the collected sound is reduced and the quality of the collected sound is deteriorated. In particular, an attempt to sharpen the directivity over the entire sound range in order to improve the zoom effect is, on the other hand, a sound collection SN.
There was a problem of decreasing the ratio.

The present invention solves the above problems and enables zoom sound to be picked up in synchronism with an image, and is less susceptible to noise such as vibration, proximity noise, and wind, and as a result, a video-integrated type. It is an object of the present invention to provide a microphone device that can be incorporated in a device such as a camera having a vibration source or a noise source inside, and can also reduce the size and weight of the entire device.

[0010]

In order to achieve this object, first and second omnidirectional microphones, which are arranged in a straight line at a distance from each other, and first and second omnidirectional microphones, are provided. A third omnidirectional microphone arranged on the perpendicular bisector of the line segment connecting the two, a first high-pass filter connected to the first omnidirectional microphone, and a second omnidirectional microphone Second high-pass filter, a delay device connected to the third omnidirectional microphone, a first subtractor for subtracting the output of the delay device from the output of the first high-pass filter, and a second high-pass filter A second subtractor for subtracting the output of the delay device from the output of the filter; first and second variable mixers for mixing the outputs of the first and second subtractors at different mixing ratios; And controlling the mixing ratio in the second variable mixer And it has a configuration in which the that controller.

Further, 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 integrally vibrate.

[0012]

According to the present invention, due to the above-described configuration, the low tone range is omnidirectional and the middle and high tone range is directional.
It is less susceptible to noise such as wind. In addition, since the directivity of the middle and high frequencies related to the sound image localization can be freely set by the time constant of the delay device based on stereo sound collection, effective zoom sound collection is possible. Moreover, since an omnidirectional microphone is used, there is almost no variation in sensitivity, frequency characteristics, directional characteristics, etc., unlike a directional microphone. Furthermore, when the directional 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, Is more advantageous than omnidirectional.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a microphone device according to an embodiment of the present invention. In FIG. 1, 1 is a first omnidirectional microphone, 2 is a second omnidirectional microphone which is arranged in a straight line at a distance from it, and 3 is a first omnidirectional microphone 1 and a second omnidirectional microphone. The third omnidirectional microphone is arranged on a vertical bisector of a line segment connecting the directional microphones 2. Here, the direction of the directional main axis of the microphone device is 2 at an angle formed by a line connecting the third omnidirectional microphone 3 and the first omnidirectional microphone 1 and the second omnidirectional microphone 2.
It is in the direction of arrow A on a straight line that divides it equally. Further, the direction of the directional principal axis of the right channel of the stereo is from the third omnidirectional microphone 3 to the first omnidirectional microphone 1. The direction of the directional main axis of the left channel of the stereo is from the third omnidirectional microphone 3 to the second omnidirectional microphone 2. If the angle of the directional principal axis of the microphone device viewed from the directional principal axis of the right channel is φ, the angle of the directional principal axis of the microphone device viewed from the directional principal axis of the left channel is −φ. Let d be the distance between the third omnidirectional microphone 3 and the first omnidirectional microphone 1 and the second omnidirectional microphone 2. Reference numeral 4 is a first high-pass filter that receives the output V1 of the first omnidirectional microphone 1 and cuts a low frequency range.
Is a second high-pass filter that receives the output V2 of the second omnidirectional microphone 2 to cut the low frequency range, and 5 is a delay device that receives the output V3 of the third omnidirectional microphone 3 and delays it by a time τ, 7 is a first subtractor for subtracting the output of the delay device 6 from the output of the first high-pass filter 4, and 8 is a second
2 is a second subtractor that subtracts the output of the delay device 6 from the output of the high-pass filter 5 of FIG. Reference numeral 9 is a first variable mixer for mixing the outputs of the first and second subtractors 7 and 8 with a mixing ratio of a to (1-a) and outputting an output signal VR. It is a second variable mixer which mixes the outputs of the subtractor 8 and the first subtractor 7 at a mixing ratio of a to (1-a) and outputs an output signal VL. Here, 0.5 ≦ a ≦ 1. 11 is the first
2 is a controller for controlling the mixing ratio of the variable mixer 9 and the second variable mixer 10. 12 and 13 are the first
2 are first and second equalizers for equalizing the output characteristics of the variable mixer 9 and the second variable mixer 10.

In the mid-high range that is sufficiently higher than the cutoff frequencies of the first high-pass filter 4 and the second high-pass filter 5, the output signals VR and VL of the microphone device are
It can be expressed as (Equation 1).

[0016]

[Equation 1]

Here, ω is the angular frequency of the sound wave. When the direction of the sound source viewed from the directivity main axis of the microphone device is θ, (Equation 2) is obtained.

[0018]

[Equation 2]

Here, k = ω / c, c is the speed of sound. k
In the frequency band of d << 1, {} of the first term on the right side of (Equation 1)
The inside becomes like (Equation 3) from (Equation 2).

[0020]

[Equation 3]

Here, α = τc / d. The first expression of (Equation 3) shows the directivity with θ = φ as the directivity main axis. The second expression of (Equation 3) shows the directivity with θ = −φ as the directivity main axis. VR and VL have a directivity that is a combination of these. For example, α = 0.587, φ = 60 °, kd
= 0.1, and a is a parameter (Equation 1),
When the directional patterns of VR and VL are calculated using (Equation 2), they are as shown in FIGS. In FIG. 2, when a = 1,
3 shows when a = 0.75, and FIG. 4 shows when a = 0.5. In the figure, the solid line shows the directional pattern of the right channel, and the dotted line shows the directional pattern of the left channel. That is, a =
The case of 1 corresponds to the wide angle of the camera, and the directivity main axes of the left and right channels are open. When a = 0.5, the directional principal axes of the left and right channels are the same and overlap with the directional principal axis of the microphone device. Thus, the directivity main axis can be changed according to the value of a, and stereo zoom sound can be picked up.

Next, since V1 and V2 can be ignored with respect to V3 in the low range sufficiently lower than the cutoff frequencies of the first high-pass filter 4 and the second high-pass filter 5, , And the directivity of the left and right channels becomes omnidirectional.

[0023]

[Equation 4]

As described above, according to the microphone device of the embodiment of the present invention, the bass is omnidirectional and the mid and treble is directional, so that it is affected by noise such as vibration, proximity noise, and wind. Since it is difficult, it can be installed in equipment that has a vibration source or noise source inside, such as a video-integrated camera,
It is possible to reduce the size and weight of these devices as a whole. In addition, since the directivity of the middle and high frequencies related to the sound image localization can be freely set by the time constant of the delay device based on stereo sound collection, effective zoom sound collection is possible. Further, since an omnidirectional microphone is used, there is almost no difference in sensitivity, frequency characteristic, directional characteristic, etc., unlike a directional microphone, and a low cost and stable quality microphone device can be realized. Further, since the omnidirectional microphone is not greatly affected by diffraction unlike the directional microphone, it can be easily attached to a device. It is also possible to correct the influence of diffraction etc. by a circuit. Further, as shown in FIG. 1, when the directional 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 integrally vibrate, In the mid-to-high range directional region, the attenuation of the sound pressure sensitivity in the 90 degree direction with respect to the 0 degree direction with the directional main axes of the left and right channels as respective axes is more advantageous than non-directionality with respect to vibration.

In this embodiment, first, the signals of the first and third omnidirectional microphones are combined, the signals of the second and third omnidirectional microphones are combined, and then both of them are combined. Although the combined signals of (1) and (2) were mixed by the first and second variable mixers, respectively, the same result can be obtained even if the order is changed as follows. That is, the signals of the first and second omnidirectional microphones are first mixed by the first and second variable mixers, respectively, and then the signals of the first and second variable mixers and the third omnidirectional microphone are mixed. The signals of the sex microphones may be combined with each other. This is apparent by transforming (Equation 1) into (Equation 5).

[0026]

[Equation 5]

[0027]

As is apparent from the above embodiments, according to the present invention, the first and second omnidirectional microphones, which are arranged in a straight line at a distance from each other, and the first and second omnidirectional microphones are not provided. A third omnidirectional microphone arranged on a vertical bisector of a line connecting the directional microphones, a first high-pass filter connected to the first omnidirectional microphone, and a second omnidirectional microphone A second high-pass filter, a delay device connected to a third omnidirectional microphone,
A first subtractor that subtracts the output of the delay device from the output of the first high-pass filter, a second subtractor that subtracts the output of the delay device from the output of the second high-pass filter, and first and second subtractors The first and second variable mixers for mixing the outputs of and with different mixing ratios, and the controller for controlling the mixing ratios of the first and second variable mixers are provided. Since the range is directional, stereo zoom sound can be picked up in sync with the image, and it is less susceptible to noise such as vibration, proximity noise, wind, etc., so it vibrates inside like a video-integrated camera. Can be built into equipment that has a noise source or a noise source,
It is possible to reduce the size and weight of these devices as a whole. further,
A microphone device in which the main axes of the three omnidirectional microphones are arranged in parallel and in the same direction and fixed so that the three omnidirectional microphones integrally vibrate, which is advantageous for vibration. Can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a microphone device according to an embodiment of the present invention.

FIG. 2 is a directional pattern diagram of the device when a = 1.

FIG. 3 is a directional pattern diagram of the device when a = 0.75.

FIG. 4 is a directional pattern diagram of the device when a = 0.5.

[Explanation of symbols]

 1 1st omnidirectional microphone 2 2nd omnidirectional microphone 3 3rd omnidirectional microphone 4 1st high-pass filter 5 2nd high-pass filter 6 Delay device 7 1st subtractor 8 2nd subtraction Device 9 first variable mixer 10 second variable mixer 11 controller

Claims (2)

[Claims] 1. A first omnidirectional microphone and a second omnidirectional microphone, which are arranged in a straight line at a distance from each other, and the first and second microphones.
A third omnidirectional microphone arranged on a perpendicular bisector of a line segment connecting the omnidirectional microphones, a first high-pass filter connected to the first omnidirectional microphone, and the second omnidirectional microphone. A second high-pass filter connected to the omnidirectional microphone, a delay device connected to the third omnidirectional microphone, and a second subtractor for subtracting the output of the delay device from the output of the first high-pass filter. 1 subtractor, a second subtractor that subtracts the output of the delay device from the output of the second high-pass filter, and the outputs of the first and second subtractors are mixed by changing the mixing ratio. A microphone device comprising first and second variable mixers and a controller for controlling a mixing ratio in the first and second variable mixers. 2. The omnidirectional microphones are arranged so that their directional main axes are parallel and in the same direction, and the three omnidirectional microphones are fixed so as to integrally vibrate. 1. The microphone device according to 1.