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JP2003284179

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DESCRIPTION JP2003284179
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
stereo microphone device incorporated in a video integrated camera or the like.
[0002]
2. Description of the Related Art In recent years, stereo microphones are incorporated in video
cameras and the like, and are widely used as means for recording audio with a sense of reality at
the same time as video.
[0003]
The conventional stereo microphone will be described below.
[0004]
In stereo microphones, two single directional microphones are arranged such that their
directional axes form a constant opening angle, and their outputs are left and right two-channel
signals.
In stereo microphones incorporated in video integrated cameras, it is common to synthesize a
single directional microphone using a plurality of nondirectional microphones.
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1
[0005]
First, a so-called directivity synthesis method will be described in which a single directivity is
obtained by using a plurality of nondirectional microphones.
FIG. 8 is a schematic view showing a state in which two nondirectional microphones are arranged
in a device such as a video camera. The upper side of the figure shows the front side of the
device, and the lower side shows the inner side of the device. FIG. 9 is a block diagram showing a
configuration for combining unidirectionality from two nondirectional microphones, and FIGS. 10
(a) to 10 (c) are characteristic diagrams when the sound source is positioned on the side 83a of
the directional axis of the microphone. The same figure (d)-(f) is a characteristic view when a
sound source is located in the 83b side of a direction axis.
[0006]
In FIGS. 8 and 9, 84 is a sound source, 84 a is a sound source located on the front side of the
device, and 84 b is a sound source located on the opposite side of the device. The first and
second microphones 81 and 82 are non-directional microphones. The first microphone 81 is
disposed on the front side of the device, and the second microphone 82 is disposed on the inner
side of the device. Reference numeral 83 denotes a directivity axis formed by the first and second
microphones 81 and 82. The upper tip 83a has a directivity angle of 0 ° and the lower tip 83b
has a directivity angle of 180 °. A phase shifter 85 shifts the phase of the output voice of the
second microphone 82, and an adder 86 combines the output voice of the first microphone 81
and the output voice of the phase shifter 85. The output speech of is synthesized with the phase
reversed. In FIG. 10, the solid line characteristic 91 is an audio signal collected by the first
microphone 81, and the dotted line characteristic 92 is an audio signal collected by the second
microphone 82.
[0007]
The operation of the directivity synthesis using the nondirectional microphone configured as
described above will be described below.
[0008]
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First, in order to obtain unidirectionality by using two nondirectional microphones, first and
second microphones 81 and 82 are arranged as shown in FIG.
Specifically, the first microphone 81 is disposed on the front side of the device, and the second
microphone 82 is disposed on the inner side of the device. Then, a pointing axis 83 is generated
on the line connecting the centers of the first and second microphones 81 and 82. In the case
shown, the upper end of the directional shaft 83 corresponds to the end of the device.
[0009]
In this configuration, when the position of the sound source 84 is at a position of 0 ° with
respect to the directivity axis 83 as shown by 84a, the phase relationship of the audio signals of
the first and second microphones 81 and 82 is shown in FIG. Characteristics 91 and 92). That is,
since the characteristic 92 of the sound signal collected by the second microphone 82 is
disposed at a position farther from the sound source 84 than the first microphone 81, the phase
is delayed by t1. The audio signal picked up by the second microphone 82 is input to the phase
shifter 85, and its phase is shifted by t2 to become as shown in FIG. 10 (b). Next, in the adder 86,
the audio signal from the phase shifter 85 is added in reverse phase to the audio signal from the
first microphone 81, and as shown in FIG. 10C, the audio signal whose amplitude is amplified is
output. It will be done.
[0010]
On the other hand, when the sound source 84 is at a position where the angle θ is 180 ° with
respect to the tip 83a of the directivity axis 83 as shown by 84b, the input voice is as shown in
FIG. 10 (d). That is, since the positional relationship is the reverse of the case where the angle θ
is 0 °, the phase of the input sound of the second microphone 82 advances by t1. Next, by
delaying the phase of the audio signal of the second microphone 82 by t2 by the phase shifter
85, as shown in FIG. 10 (e), the characteristics 91 and 92 become substantially in phase. Next, in
the adder 86, the audio signal from the phase shifter 85 is added in reverse phase to the audio
signal from the first microphone 81, and the output is a value close to 0 as shown in FIG. 10 (f). It
becomes.
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[0011]
Thus, when the sound source 84 is on the front side of the device as shown by 84a, an audio
signal is output as shown in FIG. 10 (c), and when it is on the opposite side of the device, FIG. As
shown in, the audio signal has a small value close to zero. Thus, a unidirectional microphone in
the direction of the tip 83 a of the directional axis 83 can be obtained.
[0012]
Next, an example of a stereo microphone using four nondirectional microphones is shown in FIG.
[0013]
In FIG. 7, 71, 72, 73, 74 are nondirectional microphones.
75 and 76 are directivity synthesis circuits. The nondirectional microphones 71 and 73 and the
nondirectional microphones 72 and 74 are respectively arranged to form a rectangular diagonal.
[0014]
The operation of the conventional stereo microphone configured as described above will be
described below.
[0015]
First, voices picked up by the nondirectional microphones 71 and 73 are input to the directivity
synthesis circuit 75, and based on the above-described directivity synthesis method, voice
forming unidirectionality is output as Lch voice. .
On the other hand, voices picked up by the nondirectional microphones 72 and 74 are input to
the directivity synthesis circuit 76, and based on the above-described directivity synthesis
method, voice having unidirectionality formed is output as Rch voice. .
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[0016]
As a result, an angle θ1 (hereinafter referred to as a “pointing angle”) formed by the left and
right pointing axes becomes a crossing angle of diagonal lines as shown in FIG. In the
conventional case, this directivity angle is set to about 120 °, and good stereo sound can be
collected when the sound source is positioned in the front direction of the camera.
[0017]
However, in the above-described conventional configuration, only the pattern shown in FIG. 3 can
be obtained while the four nondirectional microphones are used, and the directivity shown in
FIG. 3 can be obtained. In the corner, sound can be collected well for the sound source located in
front of the camera, but if the sound source is in a wide range (such as taking a picture of the sea,
etc. or shooting sports competitions in stadiums etc) There is a problem that sound can not be
collected so that the directivity angle is not sufficient and the presence of a good sound spread
can be obtained.
[0018]
An object of the present invention is to solve the above-mentioned conventional problems, and it
is an object of the present invention to provide a microphone device capable of selecting two
directivity angles using four nondirectional microphones.
[0019]
[Means for Solving the Problems] In order to achieve this object, the microphone device of the
present invention comprises first and second omnidirectional microphones disposed at adjacent
rectangular vertices, and the first omnidirectional microphone. Third omnidirectional
microphone disposed diagonally to the passive microphone, fourth omnidirectional microphone
disposed diagonally to the second omnidirectional microphone, and an output of the second
omnidirectional microphone First selection means for switching the signal and the output signal
of the third nondirectional microphone; and the output signal of the first nondirectional
microphone in conjunction with the first selection means and the fourth nondirectional
microphone Selection means for switching the output signal of the dynamic microphone, and
first directivity synthesis means for generating directivity from the output signal of the first
nondirectional microphone and the output signal of the first selection means Has a configuration
in which a second directivity synthesis means for generating a directional and an output signal of
the second non-directional output signal and said second selection means of the microphone.
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[0020]
This configuration provides a microphone device in which two directivity angles can be selected.
[0021]
The invention according to claim 1 of the present invention is a pair of first and second
nondirectional microphones disposed at adjacent vertices of a rectangle, and a pair of the first
nondirectional microphones. A third omnidirectional microphone disposed at a corner, a fourth
omnidirectional microphone disposed at a diagonal of the second omnidirectional microphone,
an output signal of the second omnidirectional microphone, and the fourth omnidirectional
microphone The output signal of the first nondirectional microphone and the output of the
fourth nondirectional microphone interlocking with the first selection means for switching the
output signal of the three nondirectional microphones and the first selection means A second
selection means for switching signals, a first directivity synthesis means for generating directivity
from the output signal of the first nondirectional microphone and the output signal of the first
selection means, and Omnidirectional microphone And a second directivity synthesis unit for
generating directivity from the output signal of the phone and the output signal of the second
selection unit. It has the effect that two of the degrees can be selected.
[0022]
According to the invention as set forth in claim 2, the directivity combining means comprises
phase shift means capable of changing the phase shift amount, and the directivity combining
means corresponds to the distance between the two nondirectional microphones used for
directivity combining. It has the effect of optimizing the amount of phase shift of the phase
shifter of the sex synthesis circuit.
[0023]
The invention according to claim 3 is characterized in that first and second omnidirectional
microphones disposed at both ends of an upper base of an isosceles trapezoid having two
diagonal lines and upper bases of the same length, and the first omnidirectional A third
omnidirectional microphone disposed diagonally of the microphone, a fourth omnidirectional
microphone disposed diagonally of the second omnidirectional microphone, and an output signal
of the second omnidirectional microphone And first selecting means for switching the output
signal of the third nondirectional microphone, and the output signal of the first nondirectional
microphone in conjunction with the first selecting means and the fourth nondirectional property
A second selection means for switching the output signal of the microphone; a first directivity
synthesis means for generating directivity from the output signal of the first nondirectional
microphone and the output signal of the first selection means; , Said second omnidirectional my
It is characterized by comprising second directivity combining means for generating directivity
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from the output signal of the lohon and the output signal of the second selection means, and the
directivity angle is 180 Because the choice of two powers and the distance between the two
omnidirectional microphones used for directivity synthesis are always constant, and the phase
shift of the phase shifter in the directivity synthesis circuit can always be the same, It has the
effect that it is not necessary to change the setting.
[0024]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
[0025]
(First Embodiment) FIG. 1 is a block diagram showing the configuration of a microphone device
according to a first embodiment of the present invention, FIG. 3 is a schematic diagram when the
directivity angle is about 120 °, and FIG. In FIGS. 3 and 4, arrows indicate pointing axes.
[0026]
In FIG. 1, 11 and 12, 13 and 14 are first to fourth nondirectional microphones, which are
disposed so as to be positioned at the apexes of a rectangle as shown, and the first and second
microphones 11 and 12 was placed on the front of the camera.
Reference numerals 15 and 16 denote first and second switches as first and second selection
means. The first switch 15 switches the second and third nondirectional microphones 12 and 13
to be described later. The second switch 16 switches the first and fourth nondirectional
microphones 11 and 14 to be connected to a second phase shifter 18a described later.
The first and second phase shifters 17a and 18a are first and second phase shifters, respectively,
to shift the sound from the first and second switches 15 and 16 by a predetermined phase.
Reference numerals 17b and 18b denote first and second adders, which are first and second
adders, respectively. The first adder 17b is used to convert the voice from the first
omnidirectional microphone 11 and the first phase shifter 17a. Is synthesized with anti-phase
speech from
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The second adder 18b combines the voice from the second nondirectional microphone 12 and
the reverse phase voice from the second phase shifter 18a.
The first and second adders 17b and 18b may have a configuration other than the adders, and if
the signals from the first and second nondirectional microphones 11 and 12 are synthesized in
reverse phase, the subtractor It may be
A first directivity combining circuit 17 is a first directivity combining means composed of a first
phase shifter 17a and a first adder 17b, and 18 is a second phase shifter 18a and a second The
second directivity synthesis circuit which is a second directivity synthesis means configured of
the adder 18b of
[0027]
The operation of the microphone device configured as described above will be described with
reference to FIG. 1, FIG. 3, and FIG.
[0028]
First, when the switch 15 switches to the A side to select the third nondirectional microphone 13
and the switch 16 switches to the A side to select the fourth nondirectional microphone 14, the
third nondirectional microphone 13 collects The voiced sound is input to the first phase shifter
17a and shifted in phase based on the directivity synthesis method described above, and then
synthesized with the voice from the first nondirectional microphone 11 in the first adder 17b. Be
done.
The voice collected by the fourth nondirectional microphone 14 is input to the second phase
shifter 18a, and after the phase is shifted based on the directivity combining method described
above, the second adder 18b The voice from the two nondirectional microphones 12 is
synthesized.
At this time, the directivity axes are as shown in FIG. 3, and the directivity angles become
diagonal crossing angles (about 120 °) as in the conventional stereo microphone.
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At this directivity angle, sound can be collected well with respect to the sound source located in
the front direction of the camera.
[0029]
Next, when the switch 15 switches to the B side to select the second nondirectional microphone
12 and the switch 16 switches to the B side to select the first nondirectional microphone 11, the
second nondirectional microphone 12 The picked up voice is input to the first phase shifter 17a,
and the phase is shifted based on the above-mentioned directivity synthesis method, and then the
voice from the first nondirectional microphone 11 and the first adder 17b It is synthesized.
Also, the voice collected by the first nondirectional microphone 11 is input to the second phase
shifter 18a and shifted in phase based on the directivity combining method described above, and
then the second adder 18b The voice from the two nondirectional microphones 12 is
synthesized. At this time, each pointing axis is as shown in FIG. 4 and the pointing angle is about
180 degrees. At this directivity angle, sound can be collected well for a sound source located
around the camera (wide area).
[0030]
Here, the switch of the first and second switches 15 and 16 may be provided with a mechanical
switch such as a slide switch in the camera body, and the setting menu provided as standard with
recent video cameras is software. It may be switched in the same manner. In any case, the user
can set it arbitrarily.
[0031]
As described above, according to the present embodiment, the directional axis shown in FIG. 3
and the directional axis shown in FIG. 4 can be switched by switching the first and second
switches 15 and 16. A sound source located as well as a wide range of sound sources around the
camera can be picked up well.
[0032]
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In the present embodiment, the phase shift amounts in the first and second phase shifters 17a
and 18a are the same between the case of FIG. 3 and the case of FIG. 4, but the cases of FIG. 3
and FIG. Because the distance between the two nondirectional microphones used for directivity
synthesis differs as indicated by L4 and L5 (L4> L5), the first and second phase shifters 17a and
18a have respective distances L4. If the phase shift amount is switched corresponding to L and
L5, better single directivity can be obtained.
That is, since the distance between the two nondirectional microphones is different between the
intervals L4 and L5, the phase difference t1 shown in FIGS. 10 (a) and 10 (d) is different.
Therefore, the amount of phase shift (t2 in FIGS. 10B and 10E) in the phase shifter may be
changed in accordance with the phase difference.
[0033]
Second Embodiment FIG. 2 is a block diagram showing a configuration of a microphone device
according to a second embodiment of the present invention. In FIG. 2, 21 and 22, 23, 24 are first
to fourth nondirectional microphones, 25 and 26 are first and second switches, and 27 and 28
are first and second directivity combining circuits. Although not shown, as in FIG. 1, a phase
shifter and an adder are provided internally. The above is the same as the configuration of FIG. 1
(the reference numerals are different). What differs from the configuration of FIG. 1 is that the
first to fourth nondirectional microphones 21, 22, 23, 24 are arranged to form a square as
shown, and the first and third nondirectional The diagonals L3 of the microphones 21 and 23,
the diagonals L2 of the second and fourth nondirectional microphones 22 and 24, and the
diagonals L1 of the first and second nondirectional microphones 21 and 22 all have the same
length. It is a point arranged at the vertex of an isosceles trapezoid having a diagonal of (L1 = L2
= L3).
[0034]
The operation of the microphone device of the present embodiment configured as described
above will be described using FIGS. 2, 5 and 6. FIG.
[0035]
Similar to the configuration of FIG. 1, the first and second switches 25, 26 are switched to select
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the directivity angle of FIG. 5 or FIG.
At this time, the distance (L2, L3) between the two nondirectional microphones used for
directivity synthesis shown in FIG. 5 is the same as the distance L1 between the two
nondirectional microphones shown in FIG. The phase shift amounts of the phase shifters (not
shown) in the two directivity combining circuits 27 and 28 may have the same characteristics.
[0036]
As described above, according to the present embodiment, four nondirectional microphones are
arranged at the apex of an isosceles trapezoid, and a switch is provided to switch the
nondirectional microphones used for directivity synthesis. The two directivity angles can be
made selectable without changing the setting of the phase shift amount in the two directivity
combining circuits 27 and 28.
[0037]
As described above, according to the present invention, in the stereo microphone device using
four nondirectional microphones, selection of two directivity angles makes it possible to mainly
use the sound source located in front of the camera. Also in stereo recording, stereo sound
recording mainly based on the spread of the sound in the case where the sound source is over a
wide range (shooting of landscapes in the sea etc., etc., etc. in the stadium etc) etc. The excellent
effect of being able to
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