JPS63144699A - Phase switching and sound collecting device for plural pairs of microphone outputs - Google Patents

Abstract

PURPOSE:To collect sounds with high sensitivity by providing a phase switcher for unidirectional microphone pairs, an output level comparator, and a phase switching controller, thereby varying the directively always corresponding to the moving of a sound source. CONSTITUTION:Unidirectional microphones are positioned on a circle with regular intervals with their axes of directively pointing out radially. The output level of a microphone 1b is compared with that of the microphone 1a about the input sound pressure from the direction of directivity Z1 of the latter 1a, the output level of the microphone 1a is decided to be larger, the controller 21 controls a phase inversion switch 31 so that the plus-side of a differential amplifier 41 is connected to the output of the microphone 1a. An output from the differential amplifier 42 of the microphone pair 2 is zero in principle. Accordingly, an output signal from the microphone 1a is taken out from an adder 50. As to an input from a central Z3 direction, outputs from the microphones 1a, 2a are decided to be larger, and inputted to the puls-sides of the amplifiers 41, 42, the difference between the output levels of the microphones 1a, 2a and between those 1b, 2b is taken out from the adder 50, then the synthetic pattern of outputs is formed to approach the sound course. In such a way, the sound collecting can be achieved with high sensitivity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a sound collection device configured by combining a plurality of pairs of unidirectional microphones used in audio communication conferences and the like.

(Prior Art) A microphone for an audio communication conference is placed at the center of a conference table in order to pick up the voices of callers located around the conference table, and its sound collection characteristics increase horizontally around the microphone's periphery. It is desirable to reduce the sensitivity of the microphone in the vertical direction as much as possible in order to improve the sensitivity and to avoid being affected by sound reflected from the ceiling or conference table surface.

An example of a conventional technique for realizing a sound pickup device having such characteristics is a combination of two biphasic microphones with their directivity axes shifted by 90 degrees.

FIG. 2 is a diagram for explaining the configuration and operation of the prior art. First, in FIG. 2a, l is a microphone having bidirectional characteristics and has a sensitivity directional characteristic as shown by the dotted line in the figure. In addition, the + and - signs in the figure are
For sound from the front and back of the microphone,
It is shown that a relative phase difference of 180 degrees occurs in the electrical signal output.

When one bidirectional microphone 1 is used, the angle B is 90 degrees with respect to the directivity axis A-A'.

For sound waves arriving from the direction B', the sensitivity is zero, so the output voltage is zero.

Figure 2 shows 9 of the first microphone where this sensitivity is zero.
By placing a second bidirectional microphone with its directivity axis set in the 0 degree direction and adding the outputs of these two microphones, it is possible to
FIG. 4 is an explanatory diagram of a method for obtaining sensitivity even to acoustic input in the degree direction, and is a diagram showing horizontal plane directivity characteristics. That is, 2
By adding the outputs of bidirectional microphones 1 and 2,
If the output is synthesized as a microphone output,
Its directional characteristics become a pattern of tuft θ + sin θ shown by the solid line, and for acoustic input from the Y - Y' direction at θ = 135° and 315°, the same pattern as shown in Figure 2a is applied. Just by changing the angle, the beam will have a directional characteristic with zero sensitivity.

(Problem to be solved by the invention) However, even in the method of arranging two bidirectional microphones at right angles as described above, there is a blind spot direction where the sensitivity is zero, so it is difficult to collect acoustic signals from this direction. There was a problem in that it was impossible to make a sound.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a sound collection device that can constantly change the directivity in response to changes in the position of a sound source and perform highly sensitive sound collection.

(Means for Solving the Problems) The present invention provides an amplification system that includes a plurality of pairs of unidirectional microphones arranged radially and a plurality of differential amplifiers corresponding to six pairs of the unidirectional microphones. In a sound device, a phase system in which the output side of one microphone and the output side of the other microphone are switched between six pairs of unidirectional microphones and are selectively connected to the input side or - input side of a differential amplifier. A switch, a comparator that compares the output levels of both microphones, and based on the comparison result from this comparator, connect the output side of the microphone with the higher output level to the input side of the differential amplifier, and a controller that controls the phase switch so as to connect the output side of the other microphone to the negative input side of the differential amplifier.

(Function) When sound is generated from the sound source, each microphone captures it. Then, in the six pairs of microphones, the outputs of both microphones are compared by the comparator, and based on the comparison result, the controller controls the phase switch, and the switch switches the output side of the microphone with the larger output to the differential. Connect it to the 10 input side of the amplifier, and connect the output side of the other microphone to the - input side of the differential amplifier. As a result, the phases of the microphone outputs of each pair are switched in the direction closer to the sound source, thereby forming a composite turn in the direction closest to the sound source. Furthermore, if the position of the sound source changes, the phase of each microboad pair changes accordingly, and the synthesis direction changes in the direction closest to the sound source.

(Example) FIG. 1 is a block diagram of one embodiment of the present invention.

In Fig. 1, Ia, lb, 2a, and 2b are unidirectional microphones, which are located on the same circumference (at equal intervals) and whose directivity axes extend outward in the normal direction to the circumference. The arrows of each microphone in the figure indicate its pointing direction.

11.12 is a converter, 21.22 is a controller, 31.32 is a phase inversion switch, 41.degree. 42 is a differential amplifier, 50 is an adder, and 60 is an electrical output terminal of the microphone device.

In FIG. 1, first, the pointing direction of the microphone 1a (
The operation when sound pressure is input from the direction Zl, which is the direction in which the sensitivity is increased, will be described.

In response to sound input from the Z1 direction, the input sound pressure of the microphone 1b paired with the microphone 1a is compared with the output level of the paired microphone using a controller or a controller.In this case, the directivity axis is It is determined that the output level of the microphone 1a arranged in the 21 direction is that of a dog. Based on this determination result, the controller 21 controls the phase inversion switch 31. At this time, the phase inversion switch 3 is set so that the output of the microphone 1a is connected to the positive side of the differential amplifier 41.

Since the output of one pair of microphones 2a and 2b is the input sound pressure from the same direction to the microphone, the output level from each microphone is determined by the comparator 1.
When compared with 2, they are equal. At this time, the control signal from the controller 22 to the phase inversion switch 32 is set to maintain the previous state, but when the output of each microphone is input to the differential amplifier 42, the amplitude is constant and the phase is are added with a difference of 180 degrees, so the electrical output from the differential amplifier 42 is theoretically zero.

Note that if a noise source exists in the vertical direction above and below with respect to the plane where the microphones are arranged, the noise source including the microphone pair 1a and lb will be removed for the same reason as the operation of the microphone pair 2a and 2b. , the electrical outputs from the six pairs of microphones are summed with their phases inverted by 180 degrees in the differential amplifiers 41 and 42, so the output becomes zero.

Therefore, only the electrical output corresponding to the acoustic signal from the Z1 direction output from the differential amplifiers 41 and 42 is input to the adder 50, and the electrical output signal of the microphone 1a is input to the output terminal 60 of the adder 5θ. It is taken out.

Next, consider a case where an acoustic signal is input from the Z2 direction. In this case, the microphone pair 1a explained earlier
, lb, 2a, and 2b are shifted by 90 degrees, so the above operation is applied as is.

Finally, the operation when an acoustic signal is input from the center direction z3 of the microphones 1a and 2a will be described. In this case as well, the comparators 1 and 12 compare the output levels of the microphone pairs 1a and 1b and 2a and 2b, which is the same as the operation described above. That is, for sound input from the z3 direction, microphones 1a and 2
It is determined that the output of a is dog, and the differential a/f41 and 4
The outputs of the microphones 1a and 2a are input to the positive side of the microphone 2. As a result, the microphone output in response to the acoustic input from the Z3 direction is (microphone 1
The value of (sum of output levels of a and 2a) - (sum of output levels of micro-holes 71b and 2b) is taken out from the adder 50.

This operation is the same no matter which direction the sound input direction is on the outer periphery of the microphone, so there is no blind spot with respect to the sound input direction.

Next, the converters 11 and 12 and the phase inversion switches 31, . In order to clarify the effectiveness of the presence of configurator and phase reversal switch 31.
The operation when there is no 32 will be described.

In this case, with respect to the input sound pressure from the z3 direction, the output of the microphone 1a is connected to the positive side of the differential amplifier 4, and the output of the microphone 2a is connected to the negative side of the differential amplifier 42. For the sake of simplicity, let us consider the rare case that the input sound pressure levels to the microphones 1a and 2a are the same. Since electrical signals having the same amplitude and a phase difference of 180 degrees are input to the adder 50, the electrical signal of the microphone device The output becomes zero, and the desired normal operation is no longer performed in response to acoustic input from the z3 direction. This operating state corresponds to the input sound pressure condition from the Y direction shown in FIG. 2 of the conventional example.

For the reasons for operation described above, it is understood that the comparator, the phase inversion switch, and the controller that controls them are essential device functions for configuring the present microphone and realizing desired characteristics.

In the embodiment of the present invention, the case where two pairs of microphones are combined is described, but when a microphone with sharp directional characteristics is used, in order to cover the entire circumference,
It is necessary to increase the number of microphone logarithms, and in this case, it is sufficient to prepare the same number of comparators, controllers, phase inversion switches, and differential amplifiers as the number of microphone logarithms. In this case as well, the principle and procedure of operation are the same as described above.

Next, FIG. 3 shows the results of determining the level change characteristic due to the angle change in the horizontal plane direction with respect to the -th order tilt type unidirectional microphone, depending on the number of microphones used. From this figure, in the case of 4 wires, 3d at 90 degree intervals.
Amount of decrease in B: 6 lines #, 60 It 1.2
8 dB reduction tt, 45 u Q,
It can be seen that it is 5d13 tt.

As a result, by selecting the number of unidirectional microphones to be used depending on the number of callers, etc., it is possible to collect sound radiated from the horizontal direction of the arrayed surface with less change in level. It is possible to provide a donut-oriented microphone that can reduce the output level against indoor noise coming from above and below the microphone surface, while also reducing the amount of acoustic coupling by arranging the sound receiving speaker above and below the microphone surface. This has the advantage of providing a sound pickup device that can reduce the amount of feedback and suppress the occurrence of howling.

Although this example shows the case where the microphones are arranged on the circumference, it is possible to arrange the microphones in any arrangement such as an ellipse or a rectangle depending on the arrangement of conference callers. The functional effect of the sound collection device is not lost.

(Effects of the Invention) As explained above, according to the present invention, in each pair of microphones, the outputs of both microphones are compared, and the one with the larger output is connected to the input side of the differential amplifier.
A composite turf of each microphone output is formed in the direction closest to the sound source, and the direction can be switched as the position of the sound source changes. Therefore, there is an effect that highly sensitive sound collection can be performed by changing the directivity for a sound source whose input direction is not constant.

[Brief explanation of the drawing]

Figure 1 is a block diagram of an embodiment of the present invention, Figure 2a is a horizontal plane directional characteristic diagram of a conventional bidirectional microphone, and Figure 2 is a composite of two bidirectional microphones arranged at right angles. The directivity characteristic diagram, FIG. 3, is a characteristic diagram of the number of microphones and the level change in the horizontal plane direction according to the present invention. 1.2... Bidirectional microphone, l'l, lb, 2
2! L, 2b...unidirectional microphone, 11.1
2... Comparator, 21.22... Controller, 31.32... Phase inversion switch, 41.42...
°Differential amplifier, 50...adder, 60...output terminal. Figure 1: Horizontal directivity characteristics of conventional bidirectional microphones Figure 2:
Figure a Composite directional characteristic diagram of two bidirectional microphone cophones arranged at right angles. Figure 2. Number of microphones according to the present invention and level change characteristic diagram in the horizontal plane direction. Figure 3.

Claims (1)

[Claims] A sound collection device comprising a plurality of pairs of unidirectional microphones arranged radially and a plurality of differential amplifiers corresponding to each pair of the unidirectional microphones, comprising: For each pair of directional microphones, a phase switcher is provided that switches between the output side of one microphone and the output side of the other microphone and connects the output side to the + input side or the - input side of the differential amplifier. A comparator that compares the output levels of the microphones. Based on the comparison result from this comparator, the output side of the microphone with the higher output level is connected to the + input side of the differential amplifier, and the output side of the other microphone is connected to the positive input side of the differential amplifier. and a controller for controlling a phase switch so that the phase switch is connected to the negative input side of a differential amplifier.