JPS60103900

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DESCRIPTION JPS60103900
[0001]
The present invention relates to a system for picking up sound with a microphone, and it is
intended to pick up a target sound S that is going to be picked up in noise N and to pick up S / N.
The present invention relates to a microphone system in which sensitivity is improved only for
sounds around a target sound. (Background) In the past, in order to pick up the target sound in
the noise with high S / N, when the microphone is directed to the sound source, the sensitivity to
sound incident from other than the direction of the sound source is low. A so-called directional
microphone is used. In general. If a microphone with primary sound pressure gradient directivity
is used, but the target sound is picked up with a good S / N ratio to l 侍, second- or higher-order
ejection gradient called gun microbon etc. Use a microphone with directivity. FIG. 1 is a
directivity pattern of a primary sound pressure gradient directional microphone. In this
conventional microphone, all the noise N between the sound source and the microphone is
picked up as it is in order to use the target sound S to be on the directivity main + Iiil Y shown in
FIG. I will. When the conventional micro-bon is used in conjunction with a video camera or Bmmi
camera, the screen focuses on the target and the sound is coming out despite the fact that the
surroundings are blurred. In addition to the target sound S, ambient noise N may be mixed, and
in some cases, the target sound S may be canceled by the noise N and may not be heard. In other
words, in the conventional microphone, high-order directivity is given to increase the S / N, and
only the incident sound is selected according to the direction. There is a drawback to picking up.
Another conventional microphone is a synthetic microphone as shown in FIG. In this microphone,
the microphones / MI and M2 are placed at a constant distance with the directivity main Ilib
matched, and high-order directivity is obtained by subtracting the output signal. The Katsuko
directivity good (& is noisy five to Kurai貿 between the microphone and the sound source would
be sleep as sound collection of, had similar disadvantages as the first conventional example.
(Objective) The purpose of this invention is to make the sound in one place more sensitive than
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the sound in another place, just as the camera lens can only focus on a certain place. To provide
a microphone system that sounds. Also, another object of the present invention is. Only the
sound in a specific place is more sensitive than the sound in other places «, and S / Nlil.
<The purpose is to provide a microphone system capable of picking up sound. (Outline) The
feature of the present invention is that the directivity main axis of each directional microphone is
directed to the target sound S to maximize the S / N of the microphone output signal of the same,
and the time delay By matching only the target sound signal in the output signal of each of the
microphones 1 on the time axis and adding and combining these output signals, the purpose 1 fs
whose phases are aligned on the time axis is constructively large The noise component becomes
an amplitude, and the noise component becomes an original amplitude with no phase alignment
on the time axis, resulting in an improvement in S / N. Further, another feature of the present
invention is that, in addition to the above features, a band pass filter that passes only the
frequency of a predetermined frequency band of the microbon output is provided to further
improve the S / N. EXAMPLES The invention will now be described by way of example. The side
view shows a first embodiment of the present invention in which two directional microphones
are used. In this embodiment, as is clear from the figure, two microphones M1 and M2 whose
directivity main axes are directed to the direction of the sound source P are spaced apart by a
distance. Further, the distance between the microphone M1 and the sound source P is L1 and the
distance between the microphone M2 and the sound source P is L2. Further, the angle between
the directivity main axes of the microphone M1 is set to θ1 with reference to the line connecting
the microphones M1 and M2, and the angle between the directivity main axes of the microphone
M2 is 02. Furthermore, in the example of FIG. Since L 2> L I, a time delay circuit io of delay time
τ is inserted into the output circuit of the microphone M 1 and an adder 2 o is added which
adds the output of the time delay circuit 10 and the output of the microphone M 2. I am jealous.
Next, the operation of this embodiment will be described on the assumption of the following
specific example. Micropong M1 and M2 with dimensions of 8m (frontage) x 16m (depth) xsm
(island) from the front of the rectangular room from the front to the side wall on both sides of
the place C The main axis is oriented at ° C. At this time, the distance ML between the
microphones M1 and M2 is L = 8 m, the directivity of the microphone M1 is not a reference line
connecting the microphones M1 and M2, and the angle θ1 is θ1 = 60 °, and the width of the
microphone M2 is θ2 It was -60 °. At this time, the distance L1 between the microphone M1
and the old person P is calculated from the following equation (11). On the other hand, the
distance L2 between the microphone M2 and the old person P is derived from the equation (2).
The time difference τ from when the target sound S emitted by the late P is incident on the
microphone M1 to when it is incident on the micropon M2 is expressed by equation (3), where C
is the sound speed. In this specific example, Ll from the above formulas (1) to (3). When L2 and
τ are given, LI = 4 m, L2 = 69 m, and τ = 85 ms. Therefore, the output signal of the microphone
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M2 shown in C of FIG. 4 is output as the target sound S with a delay of 8.5 ms for the output
signal of the microphone M1 of FIG. In this specific example, a time delay circuit 10 with a delay
time of 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 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 / combined by the adding circuit 20, borrowing of the waveform in FIG.
According to the above-mentioned specific apparatus, the signal part of the target sound S is
amplified by about 6 dB, and the signal of the other part (added to noise) is increased by about 1
dB. As a result, it was equivalent to the fact that only the target sound S emitted by the old P was
amplified by 6-1 = 5 dB, and the S / N could be improved by 5 dB. FIG. 5 shows a specific circuit
example of this embodiment. However, the time delay circuit unit 10 is a block diagram. VRI and
VB2 are intended to appropriately control the amplitude of the signal from the first micro-bon
input to the input terminals 1 and 2, and in this circuit example, the target sounds S1 and 82
have the same amplitude. Used. The time delay circuit unit 10 uses 512 stages of BBDs as the
time delay element 10a, and the clock pulse IOb that has been successfully applied is 60 KHy. VR
& in the summing circuit 20 determines the overall amplitude and determines the input
amplitude for the device connected to the output terminal 30. FIG. 6 shows an application of the
first embodiment. This application example is an example in which three microphones are used,
and the time delay circuit τ1. There is a work to connect τ2. Next, a second embodiment of the
present invention will be described. This embodiment differs from the first embodiment in that in
the first embodiment, C is set to the value obtained by the time delay circuit unit 100 time delay
匍 4hj j (3), and 1S can be extracted. Although the location is only in the vicinity of the sound
source P, 7 · 1 and by an external signal, it is also possible to change flrj which is the time delay 4
by equation (3) to expand the location where sound can be extracted. And even if the sound
source is moving, it is in a point where it is possible to go along with ili.
The present embodiment will be described with reference to FIG. In the seventh embodiment, the
microphones M1 and M2 are arranged in the same manner as in FIG. 6, but there are four sound
sources: p, + P2 r P3 and P4. One-dotted line τ 8. Τ b, τ. The time difference between the
arrival of the waves to the two microphones M1 and M2 is τ8. τ b, τ. Of the sound source The
case where the user processing time of the time delay circuit unit 10 is set to TbK is shown in
FIG. 3, 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 & (τ 8 τ τ b), the phases will be intensified with respect to the sound
source on the alternate long and short dash line τ 8 and reinforced. From the relationship
between the microphones M1 and M2, the place where the sound can be extracted is It becomes
a spread circular area Sa. At this time, the sounds from the sound sources PI and P2 are
emphasized as the target sound. The same busy delay time τ C (τ. If set to <τ b) K, the place
where the sound can be extracted is a circular area Sc, and the sound from the sound source PI r
P31 P4 is emphasized. It should be noted that when picking up sounds in the areas Sa and Sc, the
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sensitivity is inferior compared to picking up the sounds in the area sb. FIG. 8 shows a specific
circuit example of this embodiment. In the figure, VRl and VB2 are for controlling the amplitudes
of the signals from the microphones to the input terminals '1 and 2'. The delay circuit 10
includes a BBD or a CCD between Q, and the link pulse control circuit 40 may be a voltage
control circuit (VCO) 41 and a control voltage generation circuit 42 at the voltage + b control
signal 4. An external signal input to the external signal input terminal 4 is converted into an
appropriate DC + blJ control voltage by the control 11 L pressure generation circuit 42, and the
VCO 41 is manually operated to change the oscillation frequency of the clock pulse. VB2 in the
summing circuit 20 determines the overall amplitude and determines the input amplitude for the
device which is connected to the output terminal 6. FIG. 9 shows one application of this
embodiment. This application example is an example in which 51 microphones are used, and in
the output circuit of the microphones M1 and M2 other than the microphone U-phone M6 which
is jinj ′ ′, h · et al. There is one to connected. In addition, the time delay IAfi of each J1 controls
the clock pulse according to the external signal when it is input to the external signal input
terminal 4-changes the oscillation frequency of the clock pulse of the knock pulse control circuit
40 '. It depends on you.
In the second embodiment described above, when the directivity main axis of each microphone
can be moved, only the sound of the sound source can be pinked up even when the sound source
moves. That is, in this case, the movement of the sound source is tracked, the directivity main
axis of each microphone is moved, and each microphone is always directed in the direction of the
sound source. On the other hand, time delay circuits with variable delay amount are connected to
all the microphone output circuits, and the delay 11 is changed according to the movement of
the sound source. In this case, it is convenient to electrically disconnect and use the time delay
circuit connected to the microphone farthest from the sound source. FIG. 10 shows a sixth
embodiment of the present invention. In the figure, 50. 51 indicates a band pass filter, and the
other gradients indicate the same as or equivalent to FIG. The band pass filter 60.51 of this
embodiment has a reproduction band of 300 Hz to 5 KHz. Kneading is insufficient for iaiai, but as
a micro-bon system used for the recording of Fa Fa, C is a sufficient band. In the first
embodiment described above with reference to FIG. 6, while the signal component is amplified to
about 6 dB, the noise component is also amplified by about 1 dB. However, as shown in the
present embodiment, when the band pass filter 50.51 is inserted in the microphone output
circuit, the increase of the noise N at the low frequency component and the high frequency
component is prevented, and the time delay circuit 10 Can prevent the leak of clock pulses. FIG.
11 shows an example of a specific circuit of the fifth embodiment. However, the time delay
circuit unit 10 is shown as a flock diagram. In the figure, VRI and VB2 are for properly
controlling the amplitudes of the signals from the microphones input to the input terminals 1
and 2, respectively. The time delay circuit 10 uses 512 stages of BBDs as delay elements, and the
clock pulse applied at this time is 50 KHz. Band pass filter 50. The reproduction band of 51 was
500 Hy and 5 KHz. The VH 2 of the summing circuit 20 determines the overall amplitude of the
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microphone system and determines the input amplitude for the device connected to the output
terminal 30. FIG. 12 shows an application of the third embodiment. The application example is an
example using three high-order sound pressure gradient directional microphones, and the sound
source P of the target sound is also the farthest from the tail microphone (in this case, the
microphone M6) to the outputs of the microphones M1 and M2. The delay circuits In and I + are
connected, and a band pass filter 50.51. 52 is connected to the outputs of the microphones M +,
M2 and M6.
In the sixth embodiment described above, the band pass filter is inserted after the time delay
circuit, but of course it may be provided on the output side of the adding circuit 20. In this way,
only one band pass filter is required, which is efficient. (Effects) According to the present
invention, it is possible to emphasize only the target sound S and raise the S / N by the il
according to the present invention. Therefore, unlike the S / N improvement by the conventional
directional microphone, the target sound S appears There is an effect of taking out only the
sound that is only in the very periphery of the sound source P that is present. That is, the noise
between the sound source P and the microphone is relatively smaller than when the sound is
collected by the conventional directional microphone, and the camera blurs other than the target
point to make the object clearer like the lens of the camera. Produces the same effect as Also, by
combining the present invention with a video camera etc., it is possible to make the sound and
the video coincide with each other.
[0002]
Brief description of the drawings
[0003]
Fig. 1 shows the sameness pattern of the primary sound pressure gradient directional
microphone, Fig. 2 shows the structure of the conventional high-order sound pressure gradient
directional microphone, and Fig. 6 shows the structure of the first embodiment of the present
invention. 4 is a diagram showing the state of signals of 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 7 is an explanatory
view of the second embodiment of the present invention, FIG. 8 is a circuit diagram showing one
specific circuit of the second embodiment, and FIG. 9 is a block diagram of one application
example of the second embodiment, FIG. FIG. 1D is a block diagram of a third embodiment of the
present invention.
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FIG. 11 is a circuit diagram showing a specific circuit of the third embodiment, and FIG. 12 is a
circuit diagram of an application example of the sixth embodiment. 1.2 ... input terminal, 10. I + · ·
Time delay circuit, 20 · · · Adder circuit, 30 · · · Output terminal, 50-52 · · · Band pass filter, Ml, M
2 ° M 6 · · · · · · · · · · · · · · from the sound source 1 2 2 3 4 Figure 6 Figure 7 Figure 8 Figure 142
O Figure 210
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