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JPH05284589

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DESCRIPTION JPH05284589
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
microphone apparatus suitable for use in, for example, a video camera apparatus or a tape
recorder.
[0002]
2. Description of the Related Art In recent years, small portable video camera devices such as socalled 8 mm video camera devices have been in widespread use. Although such small portable
video camera devices are usually provided with a monaural type microphone device, since the
recent increase in audiovisual (AV) orientation of users in recent years, stereotype microphone
devices have been gradually provided. It has Conventionally, two directional (unidirectional)
microphone units are used as stereo microphone devices provided in the small portable video
camera device etc. The two directional microphone units are, for example, one for the right
channel that mainly collects sound in the right direction, and the other for the left channel that
mainly collects sound in the left direction, each at an appropriate angle. Will be installed. At the
same time, since the directional microphone unit is susceptible to wind, vibration, etc., a
windshield covering the microphone unit, a suspension for absorbing vibration, etc. are also
provided together.
[0003]
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1
However, since a stereo type microphone device using the directional microphone unit has to be
provided together with the windshield and the suspension etc., the installation area etc. becomes
large, and in recent years It was difficult to cope with miniaturization. Some stereotype
microphone devices using the above directional microphone unit have directivity in the middle
and high regions and exhibit characteristics close to non-directional characteristics in the low
region, but this is a video camera device of the main body In addition to the complexity of the
assembly process when installing on the same etc., there is also a limit in the part accuracy, so it
is difficult to control the above-mentioned characteristics, resulting in large variations in
characteristics.
[0004]
The present invention has been made in view of the above-mentioned problems, and it is possible
to obtain the same characteristics as a directional microphone unit by using two nondirectional
microphone units that are not easily influenced by wind or vibration. The purpose is to provide a
microphone device. Another object of the present invention is to provide a microphone device
which can obtain the same characteristics as a directional microphone unit by using two
nondirectional microphone units and can be stereo.
[0005]
According to the present invention, first and second nondirectional microphone units provided
close to each other, an output from the first microphone unit and the second microphone unit are
provided. First adding means for adding the outputs of the first, a low pass filter to which the
output from the first adding means is supplied, and phase shifting means to which the output
from the second nondirectional microphone unit is supplied And subtracting means for
subtracting the output from the phase shift means from the output from the first microphone
unit; and second adding means for adding the output from the low pass filter and the subtraction
output from the subtracting means And outputting the addition output from the second addition
means as an audio signal. Further, according to the present invention, there are provided first
and second nondirectional microphone units provided close to each other, an output from the
first nondirectional microphone unit, and a signal from the second nondirectional microphone
unit. A first addition means for adding the output, a low pass filter to which the addition output
from the first addition means is supplied, and a first transfer to which the output from the second
nondirectional microphone unit is supplied Phase means, first subtracting means for subtracting
the output of the first phase shifting means from the output of the first microphone unit, the
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output from the low pass filter and the subtraction output from the first subtracting means A
second adding means for adding processing, a second phase shifting means to which an output
from the first nondirectional microphone unit is supplied, and the second nondirectional
microphone unit Second subtracting means for subtracting the output of the second phase
shifting means from the output of the second phase adding means, and third adding means for
adding the subtraction output from the second subtracting means and the output from the low
pass filter , And the addition output from the second addition means is a first audio signal, and
the addition output from the third addition means is output as a second audio signal. Solve.
[0006]
In the microphone device according to the present invention, the first nondirectional microphone
unit and the second nondirectional microphone unit are provided close to each other, and the
output from the first microphone unit and the second microphone unit are provided. The
addition output from the second addition means is added by the first addition means, and the
addition output is supplied to the second addition means via the low pass filter, and the output
from the second nondirectional microphone unit is Through the subtraction means, the output of
the phase shift means is subtracted from the output of the first microphone unit, and the
subtraction output from the subtraction means is supplied to the second addition means. The
output from the low-pass filter and the output from the subtraction means are added by the
second addition means, and the addition output from the second addition means is an audio
signal By employing a configuration that is output, to obtain an audio signal having
characteristics of a chromatic directional microphone unit with a non-directional microphone
unit. Further, according to the present invention, the first nondirectional microphone unit and the
second nondirectional microphone unit are provided close to each other, and the output from the
first microphone unit and the output from the second microphone unit are The addition is
performed by one addition means, and the addition output is supplied to the second addition
means and the third addition means via a low pass filter, and the output from the second
nondirectional microphone unit is subjected to a first phase shift. Is supplied to the first
subtraction means through the means, and the first subtraction means subtracts the output of
the first phase shift means from the output of the first microphone unit and supplies it to the
second addition means And adding the output from the low-pass filter and the subtraction output
from the first subtraction means in the second addition means and outputting the result as a first
audio signal, and The output from the microphone unit is supplied to the second subtracting
means via the second phase shifting means, and the output of the second omnidirectional
microphone unit is supplied from the second subtracting means to the second phase shifting
means. The output of the second subtraction means is subjected to subtraction processing, and
the subtraction output of the second subtraction means is supplied to the third addition means,
and the subtraction output from the second subtraction means and the output from the low-pass
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filter in the third addition means Are added and processed as a second audio signal to obtain a
stereo.
[0007]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the microphone
device according to the present invention will be described below with reference to the drawings.
The microphone device according to the present invention comprises, as shown in FIG. 1, a first
nondirectional microphone unit 1, a second nondirectional microphone unit 2, and a first adder 3
which is a first addition means. It comprises a low pass filter 6, a phase shift circuit 4 which is
phase shift means, a subtractor 5 which is subtraction means, and a second adder 8 which is a
second addition means.
[0008]
The first nondirectional microphone unit 1 and the second nondirectional microphone unit 2 are,
for example, cylindrical electric condenser microphones having uniform characteristics as shown
in FIGS. 2 (a) and 2 (b). Be For example, the total length of the electric condenser microphone is
about several mm to 10 mm, and for example, as shown in FIG. 2A, the diaphragm 1a and the
diaphragm 2a are disposed close to each other coaxially so as to face each other. And fixed by a
connector 10 provided with a plurality of sound incident holes 10a such as holes and slits. The
distance d between the first and second nondirectional microphone units 1 and 2 is set to, for
example, about 10 mm so as to generate an appropriate phase difference between the
microphone units. As the first and second nondirectional microphone units 1 and 2, for example,
spherical ones may be used instead of cylindrical ones, and the set distance between the
microphone units may be arbitrary, and The microphone units may be installed coaxially with the
diaphragms 1a and 2a facing each other as shown in FIG. 2B.
[0009]
Next, the operation will be described. In FIG. 1, the sound collected by the first nondirectional
microphone unit 1 is converted into an electric signal and supplied to the first adder 3 and the
subtractor 5 as a sound signal. On the other hand, the sound collected by the second
nondirectional microphone unit 2 is converted into an electric signal and supplied to the first
adder 3 and the phase shift circuit 4 as a sound signal.
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[0010]
The first adder 3 adds the audio signal from the first nondirectional microphone unit 1 supplied
and the audio signal from the second nondirectional microphone unit 2 to each other.
[0011]
Here, vibration noise is generated when the diaphragm can not follow the movement when the
microphone unit is excited.
Therefore, the generation level of the vibration noise is directional. For example, as shown in FIG.
4A, when the first nondirectional microphone unit 1 is oscillated in a direction parallel to the
diaphragm 1a (in the direction of the arrow y in the figure), the diaphragm 1a is mostly It does
not vibrate. On the other hand, as shown in FIG. 3B, when the first nondirectional microphone
unit 1 is vibrated in the direction perpendicular to the diaphragm 1a (in the direction of the
arrow x in the figure), The diaphragm 1a vibrates largely. That is, assuming that the angle
between the diaphragm 1a and the vertical direction is θ, the velocity component contributing
to power generation is V cos θ, so that the directivity of the vibration noise level in the vibration
direction is eight-shaped. From this, if the vibration component in the direction perpendicular to
the diaphragm 1a can be removed, the vibration noise can be reduced. In this embodiment, the
diaphragms 1a and 2a of the first and second nondirectional microphone units 1 and 2 are
coupled by the connector 10 so as to face each other. Therefore, as shown in FIG. 4A, when the
entire microphone unit is vibrated in the arrow x direction, the diaphragm 1a of the first
nondirectional microphone unit 1 and the second nondirectional microphone The diaphragm 2a
of the unit 2 vibrates in the same direction, and the outputs of the microphone units are in
reverse phase. That is, when the diaphragm 1a of the first nondirectional microphone unit 1
moves, for example, in the direction approaching the back pole, the diaphragm 2a of the second
nondirectional microphone unit 2 from the back pole at the same speed. Move in the direction
away.
[0012]
On the other hand, when a sound wave is incident through the hole 10a of the connector 10, the
space surrounded by the first and second nondirectional microphone units 1 and 2 is sufficiently
smaller than the wavelength of the sound wave. Since the diaphragm 1a and the diaphragm 2a
vibrate in opposite directions as shown in FIG. 4B, the output of the first omnidirectional
microphone unit 1 and the second omnidirectional microphone The output of the unit 2 is in
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phase.
[0013]
As described above, the first and second nondirectional microphone units 1 and 2 are disposed
close to each other so that the diaphragm 1a and the diaphragm 2a face each other and fixed by
the connector 10, The outputs of the first nondirectional microphone unit 1 and the second
nondirectional microphone unit 2 due to the vibration noise component are in opposite phase to
each other, and the first nondirectional microphone unit 1 and the second nondirectional for
voice The outputs of the microphone unit 2 are in phase with each other.
Therefore, the vibration noise component is canceled by adding the output of the first
nondirectional microphone unit 1 and the output of the second nondirectional microphone unit 2
in the first adder 3 so that the vibration noise component is canceled. The outputs are summed
together to double. The audio signal with the vibration noise component canceled is supplied to
the low pass filter 6.
[0014]
The frequency characteristic of the audio signal whose vibration noise component has been
canceled by the above addition process is shown in FIG. The distance between the two
microphone units was 1 cm. Although there is a dip at 17 KHz in the frequency characteristic
shown in FIG. 5, this is a result of the outputs of both units being in anti-phase due to the
relationship of the wavelength of the sound wave. As can be seen from FIG. 5, the directivity is
omnidirectional at a frequency where the distance between the microphone units is sufficiently
smaller than the wavelength.
[0015]
The low pass filter 6 extracts only the low frequency component from the supplied audio signal,
and supplies it to the second adder 8 as a low frequency audio signal. The low-pass audio signal
is naturally nondirectional since the first and second nondirectional microphone units 1 and 2
are nondirectional.
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[0016]
The phase shift circuit 4 shifts the phase by adding the characteristics described below to the
audio signal from the second nondirectional microphone unit 2 supplied, and supplies this to the
subtractor 5. The subtractor 5 subtracts the audio signal from the second nondirectional
microphone unit 2 via the phase shift circuit 4 from the audio signal of the first nondirectional
microphone unit 1 supplied. As a result, a high frequency sound signal is extracted. This highpass audio signal is supplied to the second adder 8 through the high pass filter 7.
[0017]
Here, it is mainly the phase difference between the left and right ears in the low frequency band
of about 1 KHz or less that human senses the localization, and the level difference is mainly in
the high frequency band of about 1 KHz or more. However, it is difficult to provide a phase
difference in the low range when the small microphone units are used as the first and second
nondirectional microphone units 1 and 2 in order to reduce the mounting area and the
microphone unit interval is reduced. It becomes. Therefore, as described above, the low
frequency component is extracted from the audio signal of the first nondirectional microphone
unit 1 to be supplied to the second adder 8 as the nondirectional low frequency audio signal, and
By adding predetermined characteristics in the phase shift circuit 4, the phase of the audio signal
of the second nondirectional microphone unit 2 is offset and subtraction processing is performed
from the audio signal of the first nondirectional microphone unit 1. A high-pass audio signal
having directivity is generated, and this is supplied to the second adder 8 through the high pass
filter 7.
[0018]
The second adder 8 performs addition processing on the supplied non-directional low-pass audio
signal and the directional high-pass audio signal. As a result, it is possible to obtain a synthesized
voice signal in which the low band is nondirectional and the high band is directional. The
synthesized voice signal is supplied to a voice signal processing circuit or the like (not shown)
through the output terminal 9.
[0019]
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Next, the characteristics of the phase shift circuit 4 will be described. First, as shown in FIG. 6,
the microphone unit interval is d, the incident angle of voice is θ, and the voice signal output
from the first nondirectional microphone unit 1 is P0 (hereinafter referred to as P0 output), the
above. Assuming that the sound signal output from the second nondirectional microphone unit 2
is P1 (hereinafter referred to as P1 output), each frequency is ω, and the sound velocity is c, the
first and second nondirectional microphone units The outputs of 1 and 2 are expressed by the
following equation (1).
[0020]
Further, assuming that the directivity is D (θ, jω), it is expressed by the following equation 2.
[0021]
When T (jω) shown in the equation (2) is used as the low-pass filter to obtain a synthetic speech
signal as described above, the low band is non-directional as shown in FIG. Be directional.
[0022]
Here, an acoustic equivalent circuit of a simplified general capacitor type unit is shown in FIG.
In FIG. 8, the compliance of the diaphragm is represented as C0, the mass as m0, the equivalent
resistance as R0, the compliance of the back air chamber as C1, the mass as m1, and the acoustic
resistance from the rear entrance to the back of the diaphragm as R1. ing.
The acoustic equivalent circuit shown in FIG. 8 guides the P1 output to the back of the
diaphragm through a network consisting of the acoustic resistance R1, the compliance C1 of the
back air chamber, and the mass m1, and is differentially different from the P0 output. Directivity
is obtained by synthesizing. In order to obtain this directivity, conditions as shown in Equation 3
below are generally used.
[0023]
Assuming that the characteristic of the phase shift circuit 4 which is the transfer characteristic of
the network viewed from the P1 output side is H (jω), the audio signal obtained by the
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subtracter 5 is expressed by the following equation 4 Can be represented by
[0024]
Although there is θ on the right side of the equation shown in the above equation 4, since it is
inconvenient that the above H (jω) is a function of θ, this is eliminated.
That is, when ωd / c is small, an approximate relationship as in the following equation 5 holds.
[0025]
Substituting the equation shown in the equation 5 into the equation shown in the equation 4, the
equation shown in the following equation 6 is obtained.
[0026]
The equation shown in Equation 6 can be rewritten as the equation shown in Equation 7 below.
[0027]
Therefore, the above H (jω) can be expressed by the following equation (8).
[0028]
Substituting the equation shown in the equation 3 which is the condition of the directivity into
the equation shown in the equation 8, the above H (jω) is expressed by the equation shown in
the following equation 9.
[0029]
Assuming that the phase shift circuit 4 has the characteristic H (jω) given by the above equation
9 and is normalized by the P0 output, the calculated directional frequency characteristic of the
high-pass audio signal from the subtracter 5 is as shown in FIG. As shown in.
[0030]
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Next, when the phase shift circuit 4 has the characteristic H (jω) shown by the equation 9, the
calculated directional frequency characteristic of the synthetic speech signal which is the
addition output from the second adder 8 is shown in FIG. Shown in.
In the above calculation, the distance between the first and second nondirectional microphone
units 1 and 2 is 1 cm, the cut-off frequency of the low pass filter 6 is 1 KHz, and the sharpness
(Quality factor) is 0.9. The cutoff frequency of the high pass filter 7 is 1 KHz, and the sharpness
is 1.5.
Further, the gain of the low pass filter 6 is set to 0.5 in order to equalize the levels of the lowpass speech signal and the high-pass speech signal.
It can be seen that the synthetic speech signal in FIG. 10 is nondirectional at 1 KHz and
directional at 1 KHz to 10 KHz.
It is to be noted that the P1 output from the second nondirectional microphone unit 2 is the back
air chamber, as can be seen from the equivalent circuit shown in FIG. Compliance C 1, mass m 1,
and a network of acoustic resistance R 1 from the rear entrance to the rear surface of the
diaphragm, hardly acting in the high region.
However, when the above-mentioned microphone device is installed in, for example, a small
video camera etc., it is possible to give directivity naturally in the high region of about 5 KHz or
more due to the diffraction effect by the camera body. Therefore, the frequency band to be
controlled as directional should be between about 1 KHz and several KHz, and the above
characteristics are sufficient.
[0031]
However, there are cases where it is desirable to add more directivity in the above-mentioned
high region. This means that the mass m1 shown in FIG. 8 is given an appropriate value, and the
characteristics of the phase shift circuit 4 are made to be the characteristics shown by the
following equation 10 from the characteristics expressed by the equation 9 Can be achieved by
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[0032]
FIG. 11 shows calculated directional frequency characteristics of the high-frequency audio signal
from the subtractor 5 when the characteristic of the phase shift circuit 4 is the characteristic H
(jω) shown by the above equation (10). The directivity frequency characteristic shown in FIG. 11
is one example, but by giving the above mass m1 an appropriate value, directivity can be further
extended to a high frequency band.
[0033]
The characteristics of the synthetic speech signal when the mass m1 has an appropriate value
are as shown in FIG. Compared with the characteristics of the synthetic speech signal shown in
FIG. 10 in FIG. 12, the directivity in the range of 1 KHz to 10 KHz can be increased, and the
directivity in the high frequency band of 10 KHz or more can also be improved. it can.
[0034]
It should be noted that whether to insert a phase shift circuit having the characteristic
represented by the above equation or to insert a phase shift circuit having the characteristic
represented by the above equation according to the purpose and the specification It should be
used properly.
[0035]
Next, as shown in FIG. 13, the same direction is directed to each of the diaphragms 1a and 2a of
the first and second nondirectional microphone units 1 and 2, and the brass rods 20 are held so
as to be 1 cm apart. Make an experiment set of a microphone device by fixing and setting the
directivity frequency characteristic of the phase shift circuit 4 as the characteristic represented
by the equation (the above-mentioned mass m1 with an appropriate value), An experiment was
tried to change the angle to 0 degree, 90 degrees and 180 degrees.
First, FIG. 14A shows the directivity frequency characteristics of the first nondirectional
microphone unit 1 and FIG. 14B shows the directivity frequency characteristics of the second
nondirectional microphone unit 2. From FIGS. 14A and 14B, it can be understood that the first
and second nondirectional microphone units 1 and 2 are omnidirectional up to approximately 10
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11
KHz.
[0036]
Next, with the microphone device shown in FIG. 13, the frequency characteristics when the
sound waves outputted from the sound source were actually collected were measured. The
frequency characteristics of the synthesized speech signal at this time are shown in FIG. As can
be seen from FIG. 15, by setting the phase shift circuit 4 to the characteristics as shown in the
above equation (10), substantially the same result as the calculationally obtained result, that is,
no directivity in the low region Thus, it was possible to obtain a synthesized speech signal having
a frequency characteristic that is directional in the high frequency band.
[0037]
Thus, the first and second nondirectional microphone units 1 and 2 which are two nondirectional
microphone units are provided close to each other, and from the first and second nondirectional
microphone units 1 and 2 The output is subjected to addition processing to generate a nondirectional low-pass audio signal whose noise component has been canceled by passing through
the low-pass filter 6 and is supplied to the second adder 8 and the second non-directivity A
predetermined characteristic is added to the output from the microphone unit 2 and subtraction
processing is performed from the output of the first nondirectional microphone unit 1 to
generate a high-pass audio signal, which is output via the high pass filter 7 Non-directional by
adding the low-pass audio signal and the high-pass audio signal in the second adder 8 and
outputting the result as a synthesized voice signal. While using a microphone unit, it is possible
to obtain an output audio signal having the same characteristics as the output audio signal from
the chromatic directional microphone unit. In addition, since a nondirectional microphone unit is
used, it is not easily affected by wind noise, and vibration noise is prevented by adopting a noise
cancellation configuration, so it is necessary to provide noise prevention means such as a
windshield and a suspension. In addition, since the installation area is not taken, it is possible to
cope with, for example, downsizing of equipment such as a video camera device, and cost
reduction can be achieved. Further, the frequency characteristic of the nondirectional
microphone unit has the same sensitivity as the directional microphone unit but has less
variation, so that it is possible to output the above-mentioned synthetic speech signal with less
variation in frequency characteristics.
[0038]
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12
Next, an embodiment in which the microphone device according to the present invention is
stereotyped will be described. When the microphone device according to the present invention is
stereotyped, for example, the configuration is as shown in a block diagram shown in FIG. The
microphone device according to the present invention in FIG. 16 includes the first nondirectional
microphone unit 11, the second nondirectional microphone unit 12, the first adder 13 as the first
addition means, and the first subtraction. Means, a first subtractor 14, a low pass filter 15, a
second addition means, a second adder 16, a first phase change means, a first phase shift circuit
18, a second phase change means And a second subtractor 20 which is a second subtracting
means, and a second adder 22 which is a second adding means. The first and second
nondirectional microphone units 1 and 2 are provided close to each other so that the diaphragm
1a and the diaphragm 2a face each other coaxially, for example, as shown in FIG. It is done.
[0039]
Next, the operation will be described. In FIG. 16, the sound collected by the first nondirectional
microphone unit 11 is converted into an electric signal, and the first adder 13, the first
subtractor 14 and the second transfer are converted as an audio signal. The phase circuit 19 is
supplied. On the other hand, the sound collected by the second nondirectional microphone unit
12 is converted into an electric signal and converted to an electric signal as the first adder 13,
the first phase shift circuit 18, and the second subtractor 20. Supplied to
[0040]
The first adder 13 adds vibration processing to the supplied audio signal from the first
nondirectional microphone unit 1 and the audio signal from the second nondirectional
microphone unit 12 so as to generate vibration noise. The component is canceled and supplied to
the low pass filter 15. The low pass filter 15 extracts only the low frequency component from the
voice signal in which the vibration noise component is canceled, and supplies it to the second
adder 16 as a non-directional low frequency voice signal. It supplies to 3 adder 22.
[0041]
The first phase shift circuit 18 has, for example, the characteristics shown in the above equation
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10, and adds the characteristics to the supplied audio signal from the second nondirectional
microphone unit 12; This is supplied to the first subtractor 14. The first subtractor 14 subtracts
the audio signal of the second nondirectional microphone unit 12 to which the above-described
characteristic is added from the audio signal of the first nondirectional microphone unit 11
supplied. Then, only the voice signal of the high frequency band which has been made directional
is extracted, and this is supplied to the second adder 16 through the high pass filter 17 as a
directional high frequency voice signal.
[0042]
The second adder 16 adds the nondirectional low-pass audio signal supplied via the low-pass
filter 15 and the directional high-pass audio signal supplied via the high-pass filter 17. The signal
is processed and output as a first synthesized speech signal through the first synthesized speech
signal output terminal 23. The first synthesized voice signal is supplied to, for example, a voice
signal processing device (not shown).
[0043]
On the other hand, the second phase shift circuit 19 has the characteristic shown in the equation
(10) as in the first phase shift circuit 18, and the first nondirectional microphone unit 11
supplied is To the second subtractor 20. The second subtractor 20 adds a predetermined
characteristic to the audio signal from the second subtractor 20. The second subtractor 20 adds
the above-mentioned predetermined characteristic from the supplied audio signal of the second
nondirectional microphone unit 2 through the second phase shift circuit 19. The audio signal of
the nondirectional microphone unit 11 is subjected to subtraction processing to extract only the
audio signal of the high-pass that has been made directional, and this is extracted as a directional
high-pass audio signal via the high-pass filter 21. The data is supplied to the third adder 22.
[0044]
The third adder 22 adds the nondirectional low-pass audio signal supplied via the low-pass filter
15 and the directional high-pass audio signal supplied via the high-pass filter 21. The signal is
processed and output as a second synthesized speech signal via the second synthesized speech
signal output terminal 24. This second synthesized voice signal is also supplied to, for example, a
voice signal processing device (not shown).
03-05-2019
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[0045]
Thus, the microphone device according to the present embodiment adds the output from the first
microphone unit 11 and the output from the second microphone unit 12 in the first adder 13 to
add the vibration noise component. The voice signal from which the vibration noise component
has been canceled is supplied as a low-pass voice signal to the second adder 16 and the third
adder 22 through the low pass filter 15, and the second non-directional signal The output from
the differential microphone unit 12 is added to the first subtractor 14 with a predetermined
characteristic added by the first phase shift circuit 19, and the output of the first microphone
unit 11 is output from the first subtractor 14. The output of the first phase shift circuit 18 is
subjected to subtraction processing, and supplied to the second adder 17 via the first high-pass
filter 17 as a high-pass audio signal. Adder 17 to the high-band speech signal from low-band
speech signal and the high-pass filter 17 and the addition processing to generate a first
synthesized speech signal output from the low-pass filter 15. At the same time, the output from
the first nondirectional microphone unit 11 is added to the second subtractor 20 by adding a
predetermined characteristic by the second phase shift circuit 19, and the second subtractor 20
The output of the second phase shift circuit 19 is subtracted from the output of the second
nondirectional microphone unit 12 and supplied to the third adder 22 as a high-pass audio signal
through the second high pass filter 21. . Then, in the third adder 22, the high-pass audio signal
from the high-pass filter 21 and the low-pass audio signal from the low-pass filter 15 are
subjected to addition processing to generate and output a second synthesized voice signal. By
taking such a configuration, it is possible to give a sense of stereo.
[0046]
As apparent from the above description, the microphone device according to the present
embodiment can obtain the same characteristics as the directional microphone unit by using two
nondirectional microphone units. For this reason, since it is not easily affected by wind noise and
vibration noise is prevented by the noise cancellation configuration, it is not necessary to provide
noise prevention means such as a windshield and a suspension, and the installation area is not
taken. It is possible to cope with the miniaturization of equipment such as a video camera device,
and to achieve cost reduction. Further, the frequency characteristic of the nondirectional
microphone unit has the same sensitivity as that of the directional microphone unit, but the
variation of the characteristics is small, so that it is possible to output the synthetic speech signal
having a small variation. In addition, the microphone device according to the present
embodiment can output the first and second synthesized speech signals that are nondirectional
03-05-2019
15
in the low band and directional in the high band, so that the level difference in the high band can
be reduced. The two omnidirectional microphone units can be used to provide a sense of stereo.
[0047]
According to the present invention, the microphone device according to the present invention is
provided with the first nondirectional microphone unit and the second nondirectional
microphone unit in close proximity, and the output from the first microphone unit and the
second one. The output from the microphone unit is subjected to addition processing by the first
addition means, and this addition output is supplied to the second addition means via a low pass
filter, and the output from the second nondirectional microphone unit is phase-shifted The signal
is supplied to the subtraction means through the means, and the subtraction means subtracts the
output of the phase shift means from the output of the first microphone unit, and the subtraction
output from the subtraction means is supplied to the second addition means The second addition
means adds the output from the low-pass filter and the output from the subtraction means, and
the addition output from the second addition means is By employing a configuration for
outputting as a signal, it is possible to output audio signal having characteristics of a chromatic
directional microphone unit with a non-directional microphone unit. Further, since the
nondirectional microphone unit is not susceptible to wind noise, it is not necessary to provide a
noise prevention means such as a windshield, and the installation area is not taken, thus
contributing to downsizing of devices such as video camera devices. The cost can be reduced.
Also, since the frequency characteristics of the nondirectional microphone unit have the same
sensitivity as the directional microphone unit but with less variation, the addition output from the
second addition means also outputs the one with less variation in characteristics. be able to. In
the microphone device according to the present invention, the first nondirectional microphone
unit and the second nondirectional microphone unit are provided close to each other, and the
output from the first microphone unit and the second microphone unit are provided. The output
of the second adding means is added by the first adding means, and the added output is supplied
to the second adding means and the third adding means via the low pass filter, and the output
from the second nondirectional microphone unit is The signal is supplied to the first subtraction
means through the phase shift means 1, and the output of the first phase shift means is
subtracted from the output of the first microphone unit by the first subtraction means to obtain
the second The signal is supplied to an adding means, and the second adding means adds the
output from the low-pass filter and the subtraction output from the first subtracting means and
outputs the result as a first audio signal. The output from the first nondirectional microphone
unit is supplied to the second subtraction means via the second phase shift means, and the
output of the second nondirectional microphone unit is output by the second subtraction means.
Subtract the output of the second phase-shifting means from the above, supply the subtraction
output of the second subtraction means to the third addition means, and in the third addition
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16
means subtraction from the second subtraction means By adding the output and the output from
the low pass filter and outputting the result as the second audio signal, stereo can be obtained.
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