JPS60103900A - Microphone system - Google Patents

Abstract

PURPOSE:To record only certain sound at the specific place more sensitively than the sound at other place and to record it with an excellent S/N ratio by maximizing an S/N ratio of each microphone output signal with a directivity main axis of each directional microphone pointing to an object sound and by adding and synthesizing output signals after only the signal of the object sound of output signals of respective microphones is coincided on a time base by utilizing a time base delay circuit. CONSTITUTION:Two microphones M1 and M2 include directivity main axis pointing to a sound source P. The microphone M1 is installed at a distance L away from the microphone M2. By using the line connecting the microphone M1 to the microphone M2 as a basis, the angle formed by the directivity main axis of the microphone M1 is theta1, and the angle formed by the directivity main axis of the microphone M2 is theta2. A time delay circuit 10 of delay time tau is inserted into an output circuit of the microphone M1, and the adder 20 is provided which adds an output of the time delay circuit 10 to an output of the microphone M2.

Description

[Detailed Description of the Invention] (Field of Application) This invention relates to a system for collecting sound with a microphone, and the present invention relates to a system for collecting sound with a microphone.
The present invention relates to a microphone system for collecting sound with good S/N ratio, and in particular, has good sensitivity only to sounds surrounding the target sound.

(Background) Conventionally, in order to pick up a target sound in a noisy environment with a good S/N ratio, when a microphone is pointed at the sound source, it has to have low sensitivity to sounds coming from directions other than the sound source. A so-called directional microphone is used. In general.
A microphone with primary sound pressure gradient directionality is used, but
In order to pick up a target sound with a good signal-to-noise ratio on a samurai, a microphone having a second-order or higher-order expulsion slope directivity, such as a gun microphone, is used.

FIG. 1 shows the directivity pattern of a primary sound pressure gradient directional microphone. In this conventional glazed microphone, all the noise N between the sound source and the microphone is picked up as it is because the target sound S is directed onto the directional main +III Y shown in Figure 1. Put it away. When using Konera's conventional Micro Bonn in conjunction with a video camera or Bmmi camera, the screen focuses on the object and blurs the surrounding area, but the sound is still coming from the object. In addition to the target sound S, ambient noise N is mixed in, and in some cases, the target sound S may be drowned out by the noise N and may not even be audible.

In other words, with conventional microphones, in order to improve S/N, high-order directivity is applied to select incoming sounds based on their direction, so all sounds with the same incident direction are left as they are. It has the drawback of picking up sound.

Another conventional microphone is a synthetic microphone as shown in FIG.

In this microphone, each microphone/MI and M2 are placed a certain distance apart with their directivity main Ilib aligned.
High-order directivity is obtained by subtracting the output signal. Although the directivity of the microphone was good (.), the noise that was placed between the microphone and the sound source was not picked up as it was, and had the same drawback as the first conventional example.

(Purpose) The purpose of this invention is to detect sounds in a specific location with better sensitivity than sounds in other locations, just as a camera lens can focus only on a specific location. Our goal is to provide a microphone system that produces sound. Also,
Another object of the invention is.

Sensitivity to sounds in a specific location is better than sounds in other locations, and S/Nlil. <To provide a microphone system that can pick up sound.

(Summary) The feature of this invention is to maximize the S/N of the microphone output signal by directing the directional main axis of each directional microphone toward the target sound S, and to use a time delay circuit in the first place. By using 1 to match only the signal of the target sound in the output signal of each microphone on the time axis and then adding and synthesizing these output signals, the target 1fS whose phases are aligned on the time axis will strengthen each other and become larger. Since the noise components do not have the same phase on the time axis, the amplitude remains the same, and as a result, the S/N ratio is improved.

Another feature of the present invention is that, in addition to the above-mentioned features, a bandpass filter is provided that passes only frequencies in a predetermined band of the microbon output, and the S/N ratio is further improved.

(Example) The present invention will be explained below using examples. The lily pad is
The first aspect of the present invention when two directional microphones are used
An example is shown.

In this embodiment, as is clear from the figure, two microphones M1 and M2, each with its directivity principal axis facing the direction of the sound source P, are placed a distance apart from each other. Also,
The distance from the microphone M1 to the sound source P is set to Ll, and the distance from the microphone M2 to the sound source P is set to L2. Also, the angle formed by the main directivity axis of microphone M1 with respect to the line connecting microphones M1 and M2 is θ1
In fact, the angle formed by the directivity principal axis of microphone M2 is set to 02. Furthermore, in the example of FIG.

Since L 2 > L I, a time delay circuit io with a delay time τ is inserted into the output circuit of the microphone M1, and an adder 2o is added to add the output of the time delay circuit 10 and the output of the microphone M2. It's slumbering.

Next, the operation of this embodiment will be explained assuming the following specific example. Micropon M1 and M2 with dimensions of 8m (frontage) x1
A rectangular parallelepiped chamber measuring 6 m (depth) x sm (island size) was placed near the walls on both sides at a location approximately 5 m from the front, with the first directional main axis facing the direction of the deceased. At this time, the distance ML between the microphones M1 and M2 is L=8m, the directional signal Mill of the microphone M1 is not the reference line connecting the microphones M1 and M2, the angle θ1 is 60°, and the deflection of the microphone M2 is θ2. -60°.

At this time, the distance L1 between the microphone M1 and the elderly person P is determined from the following equation (11).

On the other hand, the distance L2 between the microphone M2 and the elderly P is (2)
From the ceremony.

The time difference τ from when the target sound S emitted by the elderly person P enters the microphone M1 until it enters the microphone M2 is determined by equation (3), where C is the speed of sound.

In this specific example, from the above equations (1) to (3), Ll
.

Adding L2 and τ, LI=4m, L2=69m, τ
=85 msec. Therefore, the output signal of the microphone M2 shown in FIG.
A delay of 5ms is output.

In this specific example, a time delay circuit 10 with a delay time τ=8.5 msec is provided in the output signal circuit of the microphone M1. Therefore, as shown in FIG. 4, the output of the time delay circuit 10 is delayed by the time τ and coincides with the output signal picked up by the microphone M2 on the time axis. Thereafter, when the above two signals are added and combined by the adding circuit 20, the waveform of FIG. 4d becomes 111 to J.

In an experiment using the above-mentioned specific device, the signal part of the target sound S was amplified by about 6 dB], and the other part (the signal part was amplified by noise).
The signal increases by approximately 1 dB.

As a result, only the target sound S emitted by the elderly P is 6-1=5d
This is equivalent to B amplification, and the S/N can be improved by 5 dB.

FIG. 5 shows a specific circuit example of this embodiment.

However, the time delay circuit section 10 is omitted from the block diagram. VRI and VB2 are used to appropriately control the amplitude of the signals from the first microbond inputted to input terminals 1 and 2. It was used as Time delay circuit section 10
uses a 512-stage BBD as the time delay element 10a, and the hardened clock pulse IOb is 60KHy,
Met.

VR& in the adder circuit 20 determines the overall amplitude, and determines the input amplitude to the device connected to the output terminal 30.

FIG. 6 shows an example of application of the first embodiment.

This application example uses three microphones, and the time delay circuits τ1 and τ1 are connected to the output circuits of the microphones Ml and M2, which are located outside the microphone MFrH that is furthest from the sound source. It is necessary to connect τ2.

Next, a second embodiment of the present invention will be described. The difference between this embodiment and the first embodiment is that in the first embodiment, C is set to a value determined by equation (3) where the time delay circuit section 100 time delay 4hjJ is expressed, and 1S can be extracted. The location is sound source P
Although it is only in the vicinity of 7.1, the external signal changes the flrj obtained by formula (3) for the time delay 4, expanding the area from which sound can be extracted, and the sound source moves. The point is that you can follow the instructions even if you're not using it.

This embodiment will be explained using FIG. 7. 7], the microphones M1 and M2 are arranged in the same way as in FIG. 6, but there are four sound sources: p, +P2 r P3, and P4. Dot-dashed line τ8. τb, τ.

Well, the time difference between the arrival of the waves to the two microphones M1 and M2 is τ8. τb, τ. This is the trajectory of the sound source.

The case shown in FIG. 3 is the case where the time TbK is set for the time delay circuit section 10, and the place where the sound can be extracted is the narrowest and becomes sb. At this time, the sound from the sound source PI becomes the target sound and is emphasized.

If the delay time is set to τ &(τ8>τb), the phases of the sound sources on the dashed line τ8 will align and strengthen each other, and from the relationship between the directivity of microphones M1 and M2, the location where the sound can be extracted is It becomes a widening circular area Sa. At this time, the sounds from the sound sources PI and P2 become the target sounds and are emphasized.

Similarly, if we set the busy delay time τC(τ.〈τb )K,
The place where the sound can be extracted is a circular area Sc, and the sound source PI
r P31 The sound from P4 is emphasized.

Note that when picking up sounds within the regions Sa and Sc, the sensitivity is inevitably inferior to when picking up sounds within the region sb.

@8 Figure shows a specific circuit example of this embodiment. In the figure, VRl and VB2 are used to control the amplitude of the signals from the microphones input to input terminals 1 and 2 to suit the amplitude. Q extended circuit 10 is BBD or CC
When D is turned off, the rear pulse control circuit 40 has a voltage of +b.
Control generator 4, VCO 41 and control voltage generation circuit 4
It might be 2. The external signal input to the external signal input terminal 4 is converted into an appropriate DC+BL by the control 11L pressure generation circuit 42.
The oscillation frequency of the clock pulse is changed by converting it into a J control voltage and manually inputting it to the VCO 41. VB2 in the adder circuit 20 determines the overall amplitude, and J is connected to the output terminal 6.
a) Determine the input amplitude for the device.

FIG. 9 shows one application example of this embodiment. This application example is
In this example, microphones are used in 51 directions.
A time delay circuit 10 is connected to the output circuits of the microphones Ml and M2 other than the microphone U-phone M6. can be determined by controlling the clock pulse 11- by means of an external signal input to the external signal input terminal 4 or by changing the oscillation frequency of the clock pulse of the knock pulse control circuit 40'.

In the second embodiment described above, if the directivity main axis of each microphone is made movable, even if the sound source moves, only the sound of the sound source can be pinked up.

That is, in this case, the main directivity axis of each microphone is moved to track the movement of the sound source, so that each microphone is always directed in the direction of the sound source.

On the other hand, a time delay circuit with a variable amount of delay is connected to all the microphone output circuits, and the delay 11 is changed in accordance with the movement of the sound source. In this case, it is convenient to electrically disconnect the time delay circuit connected to the microphone farthest from the sound source.

FIG. 10 shows a sixth embodiment of the invention. Figure smell,
50. 51 indicates a bandpass filter, and other gradient signs indicate the same or equivalent components as in FIG. The bandpass filter 60.51 of this embodiment has a reproduction band of 300Hz to 5
KHz. For kneading,) and for iaai,
Although it is not sufficient, the Microbon system C used for Kai Fa recording has a sufficient band.

In the first embodiment described above with reference to FIG. 6, the signal components are approximately 6
dB, but the noise component is also amplified by about 1 dB. However, as not shown in this embodiment, by inserting the bandpass filters 50 and 51 into the microphone output circuit, it is possible to prevent the noise N from increasing in low frequency components and high frequency components, and to prevent the noise N from increasing in the time delay circuit 10. It is possible to prevent clock pulse leakage.

FIG. 11 shows a specific circuit example of this fifth embodiment. However, the time delay circuit section 10 is shown as a block diagram in degrees Celsius.

In the figure, VRI and VB2 are used to appropriately control the amplitude of signals from each microphone input to input terminals 1 and 2. The time delay circuit 10 used a 512-stage BBD as a delay element, and the clock pulse applied to the kneader was 50 KHz. band pass filter 50
．． The reproduction band of 51 was 500Hy, ~5KHz. VH2 of the adder circuit 20 determines the amplitude of the entire microphone system, and determines the input amplitude to the device connected to the output terminal 30.

FIG. 12 shows an example of application of the third embodiment.

This application example uses three high-order sound pressure gradient directional microphones. Delay circuits In and I+ are connected, and bandpass filters 50, 51, and 52 are connected to the outputs of each microphone M+, M2, and M6.

In the sixth embodiment described above, the bandpass filter is provided after the time delay circuit, but it goes without saying that it may be provided on the output side of the adder circuit 20. In this way, only one bandpass filter is required and efficiency is high.

(Effects) According to the present invention, it is possible to increase the S/N by emphasizing only the target sound S, so unlike the S/N improvement achieved by conventional directional microphones, This has the effect of extracting only the sounds in the immediate vicinity of the sound source P. In other words, the noise between the sound source P and the microphone is relatively smaller than when collecting sound with a conventional directional microphone, and like a camera lens, it blurs everything other than the target point and makes the target object clearer. produces an effect similar to that of

Furthermore, if the present invention is combined with a video camera or the like, it will be possible to reliably match sound and video.

[Brief explanation of drawings]

FIG. 1 is a diagram of the finger homogeneity pattern of a primary sound pressure gradient directional microphone, FIG. 2 is a configuration diagram of a conventional high-order sound pressure gradient directional microphone, and FIG. 6 is a configuration diagram of the first embodiment of the present invention. Fig. 4 is a diagram showing the state of signals in each part in the embodiment of Fig. 3, Fig. 5 is a circuit diagram showing one specific circuit of the first embodiment, and Fig. 6 is a configuration diagram of an application example of the first embodiment. , FIG. 7 is an explanatory diagram of the second embodiment of the present invention, FIG. 8 is a circuit diagram showing one specific circuit of the second embodiment, FIG. 9 is a configuration diagram of one application example of the second embodiment, and FIG. Figure 1D is a configuration diagram of a third embodiment of the present invention. FIG. 11 is a circuit diagram showing one specific circuit of the third embodiment;
FIG. 2 is a circuit diagram of one application example of the sixth embodiment. 1.2...input terminal, 10. I+...Time delay circuit, 20...Addition circuit, 30...Output terminal, 50-5
2...Band pass filter, Ml, M2゜M6...
Microphone, P... Sound source, S... Target sound coming from the sound source Michihito Hiraki, Patent Attorney Figure 1 Figure 2 Figure 3 Fang 4 Figure 6 Figure 7 Figure 8 142 O Figure 9 Figure 210

Claims (1)

[Scope of Claims] (1) The main axis of directivity is directed toward source B (Several directional microphones swayed, a time delay circuit connected to the output of each microphone, and the output of each time delay circuit are summed) and a time delay circuit for adding signals from the sound source to each of the t's.
A microphone/stem which is characterized by compensating for the gap difference in the propagation of sound waves to the tI-tropic microbone, so that the sound of the sound wave is amplified more than other waves. (2) The microphone system according to claim ii, characterized in that the time delay for the output of the microphone farthest from the M source is made zero. (3) Late for each of the above times! 3. The microphone/stem according to claim 1, wherein the time delay IAi7} of the loop circuit is controllable by an external signal. (4) a plurality of directional microphones whose directional principal axes are directed toward the sound source; a time delay circuit connected to the output of each microphone; a bandpass filter that passes only frequencies in a predetermined band of the microphone output; Both devices include an adder circuit for adding the signals time-delayed by the time delay circuit, and the time delay circuit compensates for the time difference in which the sound waves are transmitted from the sound source to each of the 1/4-directional microphones, thereby increasing the time difference between the sound waves and the sound waves. A tossing microphone/stem that amplifies the sound louder than other sounds. (5) The micropon/stem according to claim 4, wherein the time delay for the output of the microphone farthest from the sound source is set to zero. (6) The microphone system according to claim 4 or 5, characterized in that the time delay amount of each of the time delay circuits can be controlled by an external device. The microphone system according to claim 4 of the patent scope, characterized in that a pass filter is connected after the time delay circuit. (8) The microphone system characterized in that the band pass filter is connected after the addition circuit. A microphone system according to claim 4.