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JPH03131199

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DESCRIPTION JPH03131199
[0001]
A. Industrial Field of Application The present invention relates to a micropon device that uses a
pair of microphone units and obtains signals of first and second channels based on the outputs of
these microphone units. SUMMARY OF THE INVENTION The present invention is a simple
apparatus using a pair of omnidirectional microphone units and applying predetermined signal
processing to outputs from the microphone units to obtain signals of the first and second
channels. The present invention provides a microphone device which is suitable for use as a
stereo microphone device and can be downsized and easy to manufacture because the
configuration can perform sufficient vibration isolation. C9 Conventional Technology
Conventionally, there has been proposed a stereo microphone device configured to distinguish
and detect an acoustic wave propagating from the left front and an acoustic wave propagating
from the right front to obtain a signal constituting a so-called stereophonic sound. As such a
microphone device, there is one configured by using a pair of unidirectional microphone units. In
this microphone device, as shown in FIG. 8, the first and second microphone units MA and Mm
forming a pair having unidirectionality as indicated by oblique lines in FIG. Pa and Pa are
arranged and configured to form predetermined angles shown by arrows ?4 and ?8 with
respect to the front. In this microphone device, the output from the first microphone unit M is
obtained from the output terminal as a signal mainly detecting the sound propagating from the
left front, and the output from the second microphone unit M. Is obtained from the output
terminal R as a signal mainly detecting the sound propagating from the front right. Also, as
shown in FIG. 9, conventionally, as indicated by oblique lines in FIG. 9, a first microphone unit
M.sub.i having a single directivity and a second microphone unit M having two directivity are
shown. A so-called MS (Midside) type stereo microphone device has been proposed. The
microphone system of the MS system is configured such that the directional axis P of the first
microphone unit M and the directional axis P of the second microphone unit M are orthogonal to
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each other. In the output of the second microphone unit M, the output when the sound
propagating from the left is detected and the output when the sound propagating from the right
is detected are signals of opposite phase to each other. In this example, the output when the
sound propagating from the left is detected is made in phase with the output of the first
microphone unit M9.
In this microphone device, a sum signal obtained by adding the output of the first microphone
unit M and the output of the second microphone unit M by the adder 101 is output from the
output terminal as a first signal. can get. Further, in this microphone device, a difference signal
obtained by subtracting the output of the second microphone unit M from the output of the first
microphone unit MM by the subtractor 102 is obtained from the output terminal R as a second
signal. . The first signal thus obtained is a signal mainly detected from the sound propagating
from the front left, and the second signal mainly detects the sound propagating from the front
right Signal has become. That is, these first and second signals have the same directivity, and the
directivity axes make a predetermined angle in the opposite direction to the directivity axis PM of
the first microphone unit M, l. Corresponds to the detected signal. By the way, since the abovedescribed microphone device is configured using a unidirectional microphone unit, it is difficult
to miniaturize the device configuration. That is, although the microphone unit is configured to
have a diaphragm that is vibrated by propagating sound, as shown in FIG. 10, in the
unidirectional microphone unit 103, the pointing axis P vibrates. It is perpendicular to the plate
104. The diaphragm 104 has a disk shape whose diameter indicated by the arrow ? ? ? ? ?
? in FIG. 10 is equal to or greater than a predetermined length in order to realize sufficient
characteristics of sensitivity and frequency characteristics to the sound of the microphone unit
103. It is formed. The diameter of the diaphragm is about 5ff111 or more in a so-called electret
condenser type microphone unit. Further, in order to realize a predetermined directivity, the
unidirectional microphone unit 103 has a length of the support 105 supporting the diaphragm
104 in the direction of the pointing axis P shown by an arrow l in FIG. It can not be made less
than a predetermined length. Therefore, as shown in FIG. 11, when the microphone device
configured by housing the unidirectional microphone unit 103 in the outer casing 106 is such
that the center of the left and right directional axes PA, P is the front side The thickness of the
outer casing 106 indicated by the arrow in FIG. 11 can not be made equal to or less than the
diameter of the diaphragm. In addition, this microphone device can not make the width and
depth of the outer casing 106 equal to or less than a predetermined length.
In a recording device such as a so-called tape recorder or video tape recorder, when the above
microphone device is integrally attached and configured, the microphone device occupies a
volume corresponding to the outer casing 106 in the recording device. , Makes it difficult to
miniaturize the recording device. Further, in the microphone device as described above, it is
difficult to set the directivity of the microphone unit constituting the microphone device to a
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predetermined directivity and to accurately set the arrangement angle of each microphone unit. ,
Can not facilitate the design, manufacture. And, as described above, in the case of the
microphone mounting configured by using the unidirectional microphone unit, it is easy to detect
mechanical vibration as noise, that is, the noise due to the vibration has many low frequency
components, In the low frequency band, unidirectional microphone units are more sensitive to
vibration than omnidirectional microphone units. Here, the vibration acceleration is ? and the
noise output by the vibration is ?. Then, the vibration sensitivity Sv is expressed by 5V-EV / ?.
Also, assuming that the sound pressure is p and the output from which the sound pressure is
detected is E, the sound pressure sensitivity S is represented by 5r-EP / p. And, the ratio S, / S of
the vibration sensitivity to the sound pressure sensitivity is Sv / Sp??m (1 + j kda) / s (1 + j kd
a?e ? ? ?). It can be shown in). In this first equation, m is the effective mass of the diaphragm
of the microphone unit, S is the effective area of the diaphragm, and k is the ratio of the angular
frequency of the sound to be detected to the speed of sound (angular frequency / sonic speed) , D
is the acoustical effective distance between the sound source and the microphone unit, a is a
coefficient determined by the directivity of the microphone unit, and a- A-1 and a = O in both
directions. When a = ?, Sv / SP = m / S (2nd equation) As shown in FIG. 7 in which the value of
the first equation is graphed, FIG. 7 The values of S, / S, for the unidirectional microphone unit
shown by r, are larger than the values of S, / S, for the omnidirectional microphone unit shown
by r2 in FIG. 7, single It can be seen that directional microphone units are more sensitive to
vibration than omnidirectional microphone units. As described above, since the unidirectional
microphone unit is sensitive to vibration, the vibration does not propagate to the microphone
unit when attached to a portable recording device such as a so-called tape recorder or video tape
recorder. It is necessary to provide a vibration isolation mechanism.
That is, in the above recording apparatus, when the above microphone device is integrally
attached and configured, simplification of the configuration of the recording apparatus becomes
difficult due to the anti-vibration mechanism. Therefore, the present invention is proposed in
view of the above-described situation, and can be used as a stereo microphone device, and the
device configuration is miniaturized, simplified and easily designed and manufactured, and
resistant to An object of the present invention is to provide a microphone device which is
excellent in vibration characteristics and enables simplification of a vibration isolation
mechanism when attached to another device. SUMMARY OF THE INVENTION In order to solve
the above-mentioned problems and achieve the above object, the microphone device according to
the present invention comprises a pair of omnidirectional microphone units, and the output from
the first microphone unit is predetermined And subtracting the output from the second
microphone unit subjected to the signal processing to obtain a signal of the first channel, and
performing the predetermined signal processing from the output from the second microphone
unit The output from the microphone unit is subjected to subtraction processing to obtain a
signal of the second channel. In the microphone device according to the invention, signals of the
first and second channels are obtained on the basis of the output from the pair of
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omnidirectional microphone units. The signals of the first and second channels can be used as
signals of the left channel and the right channel. G. Examples Hereinafter, specific examples of
the present invention will be described with reference to the drawings. The microphone device
according to the present invention, as shown in FIG. 1, comprises a pair of first and second
microphone units M, Mz. The first and second microphone units M + and Mt are omnidirectional
microphone units, respectively, and are arranged at predetermined intervals shown by arrows in
FIG. An output from the first microphone device M + obtained by detecting the sound by the first
microphone holon unit M is sent to the non-inverting input terminal of the first subtractor 1.
Also, the output from the first microphone unit M + is sent to the inverting input terminal of the
second subtracter 3 via the first delay circuit 2. The output from the second microphone unit M2
obtained by the second microphone holon unit M2 detecting the sound is sent to the noninverting input terminal of the second subtractor 3. Further, the output from the second
microphone unit M 2 is sent to the inverting input terminal of the first subtractor 1 via the
second delay circuit 4.
The signal of the first channel is obtained via the output 5 of the first subtractor 1 and the signal
of the second channel is obtained via the output 6 of the second subtracter 3. Here, the sound
pressure sensitivity SP + of the signal of the first channel is 3 r + = S, ?3, 6?j I k D cos # ?)... It
is indicated by). In the third aspect, S1 is the sound pressure sensitivity of the first microphone
unit M1, S is the sound pressure sensitivity of the second microphone unit M2, and D is the first
and second microphone units. Is an interval between them, ? is an incident angle of sound as
shown by an arrow ? in FIG. 1, and ? is a value showing a delay amount in the second delay
circuit 4 as a phase delay angle of sound. In this microphone device, the sound pressure
sensitivity St of the first microphone unit M is equal to the sound pressure sensitivity s of the
second microphone unit M ?, and the phase delay angle ? is set to ??kD, The above third
equation is approximated as S ? # jkDS + (Cos? + 1) (fourth equation) in the frequency band of
kD <1. The sound pressure sensitivity shown by the fourth equation is, as indicated by Pl in FIG.
2, the first microphone unit M and the second microphone unit M! And a line connecting the two
microphones with the first microphone unit M1 on the front side. Similarly, the sound pressure
sensitivity Spy of the signal of the second channel is expressed by 13,, = 3, 5-j fmocat? '-? (Eq.
5). In the fifth equation, ? is a value representing the amount of delay in the first delay circuit 2
as the phase delay angle of sound. Then, the above-mentioned equation 5 is approximated as S
de 2 D j k D S z (Cosa + 1) (equation 6) as in the case of the equation 3. As indicated by P2 in FIG.
2, the sound pressure sensitivity represented by the sixth equation has a line connecting the first
microphone unit M1 and the second microphone unit M2 as a pointing axis, and This
corresponds to the single directivity in which the microphone unit M2 of the above is the front
side. Thus, since the signals of the first and second channels obtained in this microphone device
have single directivity in which the opposite direction is the front side, this microphone device is
used as a stereo microphone device be able to. Since the signals of the first and second channels
have a frequency characteristic having a slope indicated by 6 dBloct, for example, the frequency
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characteristic is corrected using a predetermined frequency characteristic correction circuit. ,
Left channel signal and right channel signal.
In the microphone device according to the present invention configured as described above, each
microphone unit M1. Since Mz has omnidirectionality, it is supported by the support member 7
such that the directions of the diaphragms 8a and 8b of these microphone units M, M are the
directions shown in FIG. 3 to FIG. 5 It can be arranged. That is, as shown in FIG. 3, the respective
microphone units) Mt and Mz may be disposed such that the respective diaphragms 8a and 8b
are on the same plane, and as shown in FIG. The diaphragms 8a and 8b may be disposed so as to
face each other in parallel, and as shown in FIG. 5, the diaphragms 8a and 8b are disposed so as
to be perpendicular to each other. May be Therefore, this microphone device is configured by
arranging the above-mentioned microphone units M + and Mz in a desired direction according to
the shape and structure of the main body of the device such as a so-called tape recorder or video
tape recorder to which this microphone device is attached. can do. Then, as shown in FIG. 3, in
the case where the microphone units M + and Mt are arranged with the respective vibrations 1Ji
8a and 8b parallel to the line connecting the microphone units M + and Mt as shown in FIG. The
thickness of this microphone device shown under the arrow in FIG. 3 can be made substantially
equal to the thickness in the direction orthogonal to the diaphragms 8a and 8b of each of the
above-mentioned microphone units Mt and Mz, thereby achieving thinning of the device be able
to. The thickness of the omnidirectional microphone unit can be set to about 211Iffi. Further,
since the microphone device according to the present invention is configured using the
omnidirectional microphone units M + and Mz, detection of mechanical vibration as noise is
reduced. Further, as shown in FIG. 6, this microphone device is a support member 9 integrally
constructed such that the above-mentioned microphone units M + and Mt are in the same
direction as the respective diaphragms 8a and 8b. By supporting the apparatus according to the
present invention, it is possible to further reduce detection of mechanical vibration as noise. That
is, in this case, the vibrations of the diaphragms 8a and 8b due to the mechanical vibrations
propagating from the outside become the same frequency and the same phase. If the effective
surface density m / s of each of the microphone units M + and Mt O) diaphragms 8a and 8b are
equal to each other, the vibration sensitivity of the omnidirectional microphone unit is Sv-(m / 5)
Since Sr------(Equation 7), the vibration sensitivity SVI of the signal of the first channel is Sv +-(m /
5) (St 5te-") (eighth) Can be expressed by
The vibration sensitivity Sv + and the sound pressure sensitivity SP ++ for the front side with ? =
0. , And the ratio S vr / S p + t. ,, Sv1 / SrI +. = M (St-3 ee-") / s (St-5 te-" "dispute)) ... (9), and each
of the above microphone units M 1. If the sound pressure sensitivities S, S of Mt are made equal
to each other, the above equation (9) becomes Sv + / S ? to) = m (1-e ? ? ?) / s (1?e?j (kD
? ?) иии ииииииииииииииииииииииииииииииииииииииииииииииии (Equation 10) Here, if the phase delay angle ? is set to ? = kD,
the ratio of the vibration sensitivity Sv1 to the sound pressure sensitivity S, 1 (. In the low
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frequency band where kD <1, as shown by ro in FIG. 7 in which the value of the above equation
10 is graphed, the ratio to the unidirectional microphone unit or the omnidirectional microphone
unit is shown. Then you are low. Therefore, when the microphone device is attached to the main
body of a device such as a tape recorder or a video tape recorder, the mechanism for supporting
the microphone device may be simple and low in anti-vibration characteristic. That is, this
microphone device is particularly suitable for use in devices such as portable tape recorders and
video tape recorders, and the configuration of a device configured using this microphone device
can be simplified. As described above, in the microphone device according to the present
invention, the signals of the first and second channels are obtained based on the outputs from
the pair of omnidirectional microphone units. Since the signals of the first and second channels
can be used as signals of the left channel and the right channel, this microphone device is
suitable for use as a stereo microphone device. And since the omnidirectional microphone unit
which constitutes this microphone device is easy to design and manufacture as compared with a
unidirectional microphone unit, this microphone device can be designed and manufactured
easily. . In addition, since this microphone device is configured using an omnidirectional
microphone unit, the microphone unit can be disposed with the direction of the diaphragm as an
arbitrary direction, and the device configuration can be miniaturized. It is not necessary to
maintain the orientation of the microphone unite with high precision, and the manufacture can
be facilitated. Furthermore, the omnidirectional microphone unit has high vibration resistance as
compared to the unidirectional microphone unit, and the vibration isolation mechanism
supporting the microphone device is simplified when the microphone device is attached to
another device. Can be
That is, the present invention is suitable for use as a stereo microphone device, and the device
configuration is miniaturized and simplified to facilitate the design and manufacture, and the
vibration resistance is good and it is mounted on another device. It is possible to provide a
microphone device capable of surface conversion of the vibration isolation mechanism.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a block diagram showing the configuration of a microphone device according to the
present invention, and FIG. 2 is a graph showing the directivity of the microphone device with
respect to sound.
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FIGS. 3 to 5 are schematic views showing the direction of the diaphragm of the microphone unit
which is the main part of the microphone device, and FIG. 3 shows the state where the respective
diaphragms are arranged on the same plane, FIG. 4 shows a state in which the respective
diaphragms are arranged to be opposed in parallel to each other, and FIG. 5 shows a state in
which the respective diaphragms are arranged to be perpendicular to each other. FIG. 6 is a
cross-sectional view showing a configuration for supporting a microphone unit which is a main
part of the microphone device. FIG. 7 is a graph showing the ratio of vibration sensitivity to
sound pressure sensitivity in the microphone device, the unidirectional microphone unit, and the
omnidirectional microphone unit. FIG. 8 is a plan view showing the configuration of the
conventional microphone device, FIG. 9 is a plan view showing another example of the
configuration of the conventional microphone device, and FIG. 10 is a single unit constituting the
conventional microphone device. FIG. 11 is a side sectional view showing the structure of a
unidirectional microphone unit, and FIG. 11 is a perspective view showing the structure of a
conventional microphone device. Ml ииииииииииииииииииииииииииииииииииииииииииииииииииииииии и и и и и и и и и и и и и и и и и 1 first
microphone unit second microphone unit first subtractor first delay circuit Second subtractor
second delay circuit
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