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JPH06261388

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DESCRIPTION JPH06261388
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone device used in meetings and the like.
[0002]
2. Description of the Related Art Conventionally, when recording minutes in a meeting, etc., all
sound in a conference hall should be recorded using an omnidirectional microphone, or
microphones should be individually recorded in front of each speaker. The sound can be
recorded either individually or collectively, or by directing a unidirectional microphone to the
speaker.
[0003]
As described above, in the conventional configuration, in order to record the voices of the
speaker from multiple directions, the case of using a nondirectional microphone and the case of
separately installing the microphones are as follows. It will be difficult to hear the sound that is
really necessary because it will also pick up and record ambient noise such as other people's
conversations at the same time.
Also, in order to record the voice of the speaker from multiple directions using a unidirectional
microphone, it is necessary to move the direction of the microphone every time the speaker
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changes, and a dedicated person for that purpose is needed. There is a problem.
[0004]
An object of the present invention is to provide a microphone device capable of changing the
directivity of the microphone to the direction of the speaker without changing the direction of
the microphone each time the speaker changes.
[0005]
According to the microphone device of the present invention, the direction of the sound source of
the sound wave is determined on the basis of a plurality of microphone elements arranged at
regular intervals and receiving the sound wave, and the outputs of the plurality of microphone
elements. Control unit for controlling the weighting of the weighting unit based on the direction
of the sound source to be obtained, the weighting unit for weighting the outputs of the plurality
of microphone elements, and the direction of the sound source obtained by the direction
detection unit And a combining unit that outputs a signal obtained by phase-matching and
adding each output of the weighting unit.
[0006]
According to this configuration, the azimuth detecting unit obtains the azimuth of the sound
source based on the outputs of the plurality of microphone elements.
Correspondingly, the control unit controls the weighting of the weighting unit to change the
directivity to the direction of the sound source.
[0007]
An embodiment of the present invention will be described below with reference to FIGS.
The microphone device of this embodiment is configured as shown in FIG. Reference numeral 11
denotes a three-dimensional coordinate system, which comprises an X-axis, a Y-axis, and a Z-axis
perpendicular to the XY plane. A microphone 1 converts a sound wave from a sound source into
an electric signal. In this embodiment, a total of 16 microphone elements A, B, C, D, E are
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arranged in an array of four columns in the X axis direction and the Y axis direction. , F, G, H, I, J,
K, L, M, N, O, P. Further, the distance between each of the microphone elements A to P is defined
by an integral fraction wavelength of the sound to be received (the distance is 8.5 cm in the case
of 1 KHz at 1?4 wavelength). A container 2 for containing the microphone 1 is a container made
of metal such as aluminum filled with a rubber material such as urethane to prevent unnecessary
resonance and fix the positions of the microphone elements A to P. A preamplifier 3 amplifies the
weak signal from the microphone 1 to such an extent that the weak signal can be processed. An
azimuth detecting unit 4 uses two microphone elements L and J in the X axis direction of the
microphone 1 and two microphone elements B and J in the Y axis direction to detect the azimuth
of the sound source from the time difference between received signals. A weighting unit 5
weights the received signals of the microphone elements A to P in order to make the microphone
1 have directivity. A delay correction unit 6 matches the phases of the reception signals of the
microphone elements A to P of the microphone 1. Reference numeral 8 denotes an addition unit,
which adds the sixteen audio signals phased by the delay correction unit 6 into an audio signal
having one directivity. The delay correction unit 6 and the addition unit 8 constitute a combining
unit 12. A control unit 7 controls the azimuth detection unit 4, the weighting unit 5, and the
delay correction unit 6. A power amplifier 9 causes the audio signal from the adding unit 8 to
meet an external output unit and performs amplification. An external output unit 10 includes an
external interface for connecting to a recording device such as an external tape recorder or a
speaker for amplifying and reproducing an audio signal.
[0008]
2A and 2B are diagrams showing an azimuth detection method, in which FIG. 2A is a block
diagram of the azimuth detection unit 4, FIG. 2B is a principle diagram of time difference
generation, FIG. 2C is a method of time difference detection, and FIG. It is a conceptual diagram.
[0009]
FIG. 3 shows a schematic view of a weighting scheme that changes the directivity of the
microphone 1.
The coefficients ?i (i = 1 to 16) used for weighting change in numerical values between 0 and 1.
FIG. 4 is a change diagram of directivity with respect to the state of weighting of each of the
microphone elements A to P. In FIG.
[0010]
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Next, the operation will be described. First, the initial operation will be described with reference
to FIG. The control unit 7 controls the weighting unit 5 to set the weighting coefficients of all the
microphone elements A to P to the maximum value (= 1), and enters a reception standby state.
The directivity of the output of the adder 8 at this time is as shown in FIG. 4 (a). Next, when a
sound at a certain level or more comes in from the sound source W (such as human voice), the
sound wave detection unit 4a of FIG. 2 (a) operates to generate a pulse waveform as shown in
FIG. 2 (c). The pulse waveform generated at this time has a time delay of ?tx because the sound
received by the microphone element L and the sound entering the microphone element J are
shifted depending on the direction of the sound source W as shown in FIG. 2B. The time interval
between the pulse waveform P1 from the comparator 4al corresponding to the microphone
element L and the pulse waveform Pj from the comparator 4aj corresponding to the microphone
element J is detected as ?tx by the time difference detection unit 4b of FIG. . The angle ?x
formed by the sound source W in FIG. 2D and the X axis is equal to the angle between the sound
source W in FIG. 2B and the axis connecting the microphone element J and the microphone
element L. In the azimuth angle detection unit 4c of FIG. 2A, the time difference ?tx in the X-axis
direction, the speed V of the sound, the detection frequency f which is the frequency of the sound
wave for detecting the time difference ?tx, the microphone element J and the microphone
element From the interval (1/2) и ? (? = the wavelength of the sound wave for detecting the
time difference ?tx), the angle ?x between the sound source W and the X axis is calculated by
the equation of Equation 1.
[0011]
?x = cos?1 (2 и ?tx и f) иииииииииииииииииииииииииииииииииииииии Equation 1 The equation of equation 2 is calculated
from the time interval ?ty of the pulse waveform of each output.
[0012]
?y = cos?1 (2 и ?ty и f) иииииииииииииииииииииии An angle between the line W ? projected on the XY plane
and the line connecting the sound source W and the origin is shown in FIG. As expressed by the
azimuth angle ? as in the above, the angle ?x formed by the sound source W and the X axis and
the angle ?y formed by the sound source W and the Y axis are calculated by the equation of
Equation 3.
[0013]
? = tan-1 (cos ?y / cos ?x)
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иииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииииии
иииииииииииииииииииииииииииииииииииииииииииииииииииииии Equation 3 control unit 7 sets weighting parameters to shift
directivity by 5 degrees in the XY plane with the X axis as 0 degree It has with respect to element
AP.
When weighting is set to a value close to 1 to the alignment of the direction of the sound source
W among the microphone elements A to P, and is set lower as the distance from the direction of
the sound source W increases, each microphone Due to the difference in the reception levels of
the elements A to P, directivity is concentrated in the direction of the sound source W in the XY
plane.
[0014]
The azimuth angle ? obtained by the azimuth detection unit 4 is sent to the control unit 7.
The control unit 7 determines the position of the sound source W on the X-Y plane from the
azimuth angle ?, selects the closest one from among the weighting parameters set in 5-degree
increments of the azimuth angle ?, and selects a weighting unit. Send to 5. The weighting unit 5
changes the weighting coefficients ?1 to ?16 of the respective microphone elements A to P in
the range of 0 to 1 in accordance with the sent parameters, and adds the output signals from the
respective microphone elements A to P together. Output. The signal output from the weighting
unit 5 has the phase of each of the microphone elements A to P adjusted by the delay correction
unit 6 in order to correct the phase shift due to the positional element in accordance with the
arrangement of the microphones 1. The adder 8 adds all the 16 signals of the microphone 1 and
outputs the result as one signal. In this case, the added signal is based on the sound wave
received with directivity of the direction of the sound source W as shown in FIG. 4 (b). The
output of the adder 8 is sent to the power amplifier 9. In the power amplifier 9, the gain of the
amplifier is increased when the external output unit 10 is a speaker or the like, and the gain is
reduced and output when the external output unit 10 is a line output for connecting to another
device. The external output unit 10 converts an electrical signal into an audio signal and outputs
the audio signal in the case of a speaker, and performs output impedance matching when
outputting to another device. The azimuth detecting unit 4 constantly monitors the sound wave
from each sound source W even after the azimuth angle ? of the sound source W is determined
once, and always sends the azimuth angle ? of the detected sound source W to the control unit
7 ing. The control unit 7 compares the information of the new azimuth angle ? with the
currently set azimuth angle ?, and sends the new parameter to the weighting unit 5 when the
azimuth angle ? changes.
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[0015]
With this configuration, even when the speaker who is the sound source W changes in a
conference or the like, the directivity of the microphone 1 can be automatically changed to the
direction of the speaker without manually moving the direction of the microphone 1 . In addition,
since it has directivity, optimal sound amplification and reproduction can be performed without
picking up surrounding noise.
[0016]
In the above embodiment, although the method of detecting the direction of the speaker based
on the time difference between the voice signals received by the two microphone elements is
adopted as the direction detection unit 4, the phase difference between the voice signals received
by the two microphone elements is detected. It is also possible to detect the direction of the
speaker by using the following method.
[0017]
In each of the above embodiments, the orientation is changed only with respect to the X-Y plane,
but it is also possible to change the three-dimensional orientation of X, Y and Z by the same
method.
[0018]
As described above, according to the present invention, the control unit controls the weighting of
the weighting unit in accordance with the direction of the sound source determined by the
direction detection unit, and the combining unit controls each of the weighting units. Since the
outputs are phased, added and output, the directivity is automatically changed to the direction of
the sound source each time the sound source changes, and only the sound wave of the sound
source can be output as a signal.
Therefore, sound can be collected with less noise such as sound waves other than the sound
source.
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