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JP2010178266

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DESCRIPTION JP2010178266
To arrange a pair of microphones having nondirectionality at a predetermined distance on the
front side of the same plane, it is possible to obtain an acoustic characteristic so as to obtain a
rotating curved surface directivity characteristic of a fan-shaped cross section in the front side
direction of the plane. Raise. SOLUTION: First and second transmission path forming circuits 4
and 5 controlled based on a detection result of a comparison circuit 2 for detecting a phase
difference of sound waves arriving to a pair of microphones 1a and 1b are delay means 8. Form a
transmission path from the primary subtraction circuit 7 to the tertiary addition circuit 9 and the
secondary subtraction circuit 10 when the arrival level of the other relevant microphone
connected to is smaller than the arrival level of the other relevant microphone From the
secondary addition circuit to the tertiary addition circuit and the secondary subtraction circuit
when the transmission path from the addition circuit to the output terminal 11 is formed and the
arrival level of the other relevant microphone is larger than the arrival level of one of the
relevant microphones And a transmission path from the secondary subtraction circuit to the
output terminal. [Selected figure] Figure 2
Microphone device
[0001]
The present invention relates to a microphone device in which a pair of nondirectional
microphones are arranged on a front side of the same plane at a predetermined distance, and
more particularly to a microphone device capable of obtaining a fan-shaped directivity
characteristic.
[0002]
04-05-2019
1
Conventionally, as a microphone device of this type, an omnidirectional microphone unit with a
single directivity (consistent with the microphone.
) A microphone unit for high frequency having a single directivity is disposed at a predetermined
position closer to the sound source than the), and a low frequency having a single directivity at a
predetermined position farther from the sound source than this microphone unit for all bands
Sound pressure gradient type unidirectional microphone having a microphone unit disposed
therein is disclosed (see, for example, Patent Document 1).
[0003]
According to this second-order sound pressure gradient type unidirectional microphone, two
microphone units having different frequency bands in high and low frequencies are disposed
apart by a predetermined distance, and a sound source corresponding to the distance The fanshaped unidirectionality can be obtained by enhancing the reception sensitivity of the sound
waves arriving from the sound source by using the delay time from.
[0004]
Japanese Patent Application Laid-Open No. 58-88994
[0005]
According to the secondary sound pressure gradient type uni-directional microphone described
in Patent Document 1 described in the background art, two microphone units having different
frequency bands in high and low frequencies are interphones as an aspect of their arrangement.
It is considered that it is difficult to provide a predetermined distance apart on the front side of
the same plane as in the case of a device, and it is likely to be in a three-dimensional arrangement
in many cases.
Also, in order to obtain a fan-shaped directivity characteristic by combining a microphone unit
having unidirectionality and a microphone unit having omnidirectionality, the directivity
characteristic of the microphone unit having unidirectionality is not impaired. It was difficult to
arrange in the case.
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2
[0006]
Therefore, the secondary sound pressure gradient type uni-directional microphone of Patent
Document 1 described in the background art is often limited to a mode in which the microphone
unit is used as a single unit.
[0007]
The present invention has been made to solve these problems, and in arranging a pair of
omnidirectional microphones separated by a predetermined distance on the front side of the
same plane, the cross section is directed in the front side direction of the plane. It is an object of
the present invention to provide a microphone device having improved acoustic characteristics
so as to obtain fan-shaped rotational curved surface directivity characteristics.
[0008]
In order to achieve the above object, in the microphone device according to the first aspect of the
present invention, a pair of microphones having nondirectionality are disposed on the front side
of the same plane at a predetermined distance apart, The comparison means for detecting the
phase difference of the arriving sound waves, the first operation means for performing the
addition of the outputs of the pair of microphones, and the output of one of the pair of
microphones correspond to the distance Delay means for giving a delay time, a second operation
means for adding / subtracting the output of the delay means and the output of the other of the
pair of microphones, the output of the first operation means, and the second Third operation
means for performing addition and subtraction of the output of the operation means, first
transmission path formation means for forming a transmission path between the second
operation means and the third operation means, and third operation The arithmetic means and
the second transmission path forming means for forming the transmission path between the
output terminals are provided, and each of the first and second transmission path forming means
includes a pair of transmission means corresponding to the direction of arrival of the sound
wave. It is switched based on the detection result of the comparison means according to the
phase difference of the sound wave which arrives at a microphone.
[0009]
Further, in the microphone device according to the second aspect of the present invention, in the
first aspect of the present invention, the first transmission path forming means determines that
the arrival level of the other relevant microphone is one based on the detection result of the
comparison means. And the transmission path from the subtracter circuit constituting the second
computing means to the third computing means when the level reached by the other one of the
microphones It has a function of forming a transfer path from the adder circuit constituting the
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second operation means to the third operation means when the level is larger than the arrival
level, and the second transfer path forming means When the arrival level of the other relevant
microphone is smaller than the arrival level of one of the relevant microphones based on the
detection result, the output from the adder circuit constituting the third arithmetic means
Forming a transmission path to the output terminal from the subtractor circuit constituting the
third arithmetic means when the arrival level of the other relevant microphone is larger than the
arrival level of one of the relevant microphones. It has a function.
[0010]
According to the microphone device of the present invention, when arranging a pair of
microphones having nondirectionality at predetermined distances on the front side of the same
plane, the output of the microphone is generated for sound waves coming from a specific angle.
On the other hand, for the sound wave coming from the direction out of the angle, the output of
the microphone can be attenuated.
Thus, for example, when a pair of microphones and a speaker are disposed on the front side of
the same plane of one case such as an intercom device, the voice signal emitted by a person
facing the pair of microphones is generated. While the large output can be obtained, only a very
small output of the microphone can be obtained with respect to the output of the speaker, so the
acoustic characteristic is enhanced so that the rotating curved surface directivity characteristic of
the cross section is obtained in the front side direction of the plane. It is possible to realize high
speed simultaneous voice communication.
[0011]
FIGS. 1A, 1B, 1C, and 1D are configuration diagrams showing an arrangement of a pair of
microphones in a microphone device according to an embodiment of the present invention.
FIGS. 2A and 2B are circuit block diagrams showing specific configurations of the microphone
device according to the embodiment of the present invention.
FIGS. 3A and 3B are directivity characteristic diagrams obtained in the microphone device
according to the embodiment of the present invention.
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[0012]
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best embodiment to which
the microphone device of the present invention is applied will be described with reference to the
drawings.
[0013]
As shown in the configuration diagrams of FIGS. 1 (A), (B), (C), and (D), this microphone device
has a pair of omnidirectional microphones (hereinafter referred to as first and second
microphones). It is said.
) 1a, 1b, for example, speakers (not shown).
And a predetermined distance L on the front side of the same plane such as a housing of an
intercom device capable of performing simultaneous voice and speech calls, corresponding to the
distance L, which will be described later Sound waves come at four different predetermined
incident angles φ 1, φ 2 φ 3 and φ 4.
[0014]
Here, the above-mentioned front side indicates the side on which the diaphragms of the first and
second microphones 1a and 1b face each other.
The predetermined incident angles φ1, φ2, φ3, and φ4 are the first incident angle “0 ° <φ1
≦ 90 °” shown in FIG. Second incident angle “90 ° <φ2 ≦ 180 °” shown, third incident
angle “180 ° <φ3 ≦ 270 °” shown in FIG. 1 (C), fourth incident angle shown in FIG. 1 (D)
Four different quadrants (hereinafter referred to as first to fourth quadrants) such as “270 °
<φ4 ≦ 360 °”. Shall be set separately.
[0015]
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5
FIGS. 2A and 2B are circuit block diagrams showing specific configurations of the microphone
devices having the first and second microphones 1a and 1b, respectively. In this microphone
device, both ends of the relay Ry constituting the comparison circuit 2, the primary addition
circuit 3 and the first and second transmission path forming circuits 4 and 5 are provided for the
first and second microphones 1a and 1b. Each is connected.
[0016]
Here, the comparison circuit 2 reaches the first and second microphones 1a and 1b at different
times corresponding to the predetermined distance L and the first to fourth incident angles φ1,
φ2, φ3 and φ4, respectively. It is for detecting the phase difference of the sound wave to be
detected, and specifically, it can be detected based on the amplitude difference.
[0017]
The primary addition circuit 3 is for adding the sound waves arriving to the first and second
microphones 1a and 1b, and on the output side thereof, the tertiary addition circuit 9 and the
secondary subtraction circuit 10 have input sides. One end is connected respectively.
[0018]
Further, to any one of the first and second microphones 1a and 1b, here, to the first microphone
1a referred to as the other corresponding microphone, the inputs of the secondary addition
circuit 6 and the primary subtraction circuit 7 One end of each side is connected, and the other
end of the input side of the secondary addition circuit 6 and the primary subtraction circuit 7 is
connected to the second microphone 1b called one of the microphones via the delay circuit 8
There is.
[0019]
Further, the first make contact P4a of the changeover switch SW4 constituting the first
transmission path forming circuit 4 is connected to the output side of the secondary addition
circuit 6, and the output side of the primary subtraction circuit 7 is a changeover switch. The
second make contact P4b of SW4 is connected to the common contact P4c of the changeover
switch SW4, and the other ends on the input side of the tertiary addition circuit 9 and the
secondary subtraction circuit 10 are connected to each other.
[0020]
Furthermore, the first make contact P5a of the changeover switch SW5 constituting the second
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transmission path forming circuit 5 is connected to the output side of the tertiary addition circuit
9, and the output side of the secondary subtraction circuit 10 is a changeover switch. The second
make contact P5b of SW5 is connected, and the output terminal 11 is connected to the common
contact P5c of the changeover switch SW5.
[0021]
Here, the delay circuit 8 is a predetermined one detected by the above-mentioned comparison
circuit 2 with respect to the sound wave that arrives at the second microphone 1b, which is
referred to as one of the first and second microphones 1a and 1b. It is for sending out with a
time delay corresponding to the distance L and the first to fourth incident angles φ1, φ2, φ3
and φ4.
[0022]
The secondary addition circuit 6 is for adding the output wave from the first microphone 1a and
the output wave from the delay circuit 8 which are referred to as the other one of the first and
second microphones 1a and 1b. It is.
[0023]
The primary subtraction circuit 7 is for subtracting the output wave from the delay circuit 8 from
the output wave from the first microphone 1a, which is referred to as the other one of the first
and second microphones 1a and 1b. .
[0024]
The tertiary addition circuit 9 adds the output wave from the primary addition circuit 3 and the
output wave from the secondary addition circuit 6 or the primary subtraction circuit 7 via the
changeover switch SW4 constituting the first transmission path forming circuit 4 It is for.
[0025]
The secondary subtraction circuit 10 subtracts the output wave from the secondary addition
circuit 6 or the primary subtraction circuit 7 via the changeover switch SW4 constituting the first
transmission path forming circuit 4 from the output wave from the primary addition circuit 3 It
is for.
[0026]
The first transmission path forming circuit 4 is composed of the above-mentioned relay Ry and
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the changeover switch SW4, and based on the detection result of the comparison circuit 2, the
first transmission path forming circuit 4 and one of the first and second microphones 1a and 1b
When the level of the sound wave reaching the second microphone 1b referred to is smaller than
the level of the sound wave reaching the first microphone 1a referred to as the other relevant
microphone, the first subtraction circuit 7 to the second make contact P4b, common While
forming a transmission path to the third-order addition circuit 9 and the second-order
subtraction circuit 10 via the contact point P4c, the level of the sound wave reaching the second
microphone 1b is compared as the level of the sound wave reaching the first microphone 1a Of
the secondary addition circuit 6 through the first make contact P4a and the common contact
P4c, the tertiary addition circuit 9 and the secondary subtraction circuit 10 Transmission path is
used for forming a.
[0027]
The second transmission path forming circuit 5 is composed of the above-described relay Ry and
the changeover switch SW5, and based on the detection result of the comparison circuit 2, one of
the first and second microphones 1a and 1b and the corresponding microphone When the level
of the sound wave reaching the second microphone 1b referred to is smaller than the level of the
sound wave reaching the first microphone 1a referred to as the other relevant microphone, the
third-order summing circuit 9 to the first make contact P5a, common While forming a
transmission path to the output terminal 11 via the contact point P5c, when the level of the
sound wave reaching the second microphone 1b is larger as the level of the sound wave reaching
the first microphone 1a, the secondary The transmission path is formed from the subtraction
circuit 10 to the output terminal 11 via the second make contact P5b and the common contact
P5c.
[0028]
In the microphone device according to the embodiment of the present invention configured as
described above, in describing the specific operation, the incident angle of the sound wave
reaching the first and second microphones 1a and 1b is “0 ° < A first quadrant with a first
incident angle of φ1 ≦ 90 °, a second quadrant with a second incident angle of “90 ° <φ2
≦ 180 °”, “180 ° <φ3 ≦ 270 °” The operation corresponding to each quadrant is
divided into a third quadrant, which is the third incident angle, and a fourth quadrant, which is
the third incident angle of “270 ° <φ4 ≦ 360 °”. The fourth to fourth operations will be
described.
[0029]
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8
First, as shown in FIG. 1A as the first operation, the first and second microphones 1a and 1b
disposed on the front side of the same plane at a predetermined distance L apart are For
example, when a sound wave having an acoustic velocity of 34000 cm / s [sec] arrives at the first
incident angle “0 ° <φ1 ≦ 90 °”, the arrival time to the second microphone 1 b is
determined by the first microphone 1 a. As compared with the arrival time, the time τ [sec]
shown in equation (1) is delayed.
τ = L · sin {(π / 2) −φ1} / 34000 (1)
[0030]
As a result, sound waves X1a (t) and X1b (t) that have reached the first and second microphones
1a and 1b can be expressed by equation (2).
X1a (t) = sin ωt X1b (t) = sin ω (t−τ) (2)
[0031]
Further, referring to FIG. 2A as the first operation, the sound wave X1a (t) arriving at the first
microphone 1a is transmitted to the comparison circuit 2, the primary addition circuit 3, the first
and second transmission paths. The relays Ry constituting the forming circuits 4 and 5, the
secondary adding circuit 6 and the primary subtracting circuit 7 are respectively sent.
On the other hand, the sound wave X1b (t) arriving at the second microphone 1b is sent out to
the relay Ry constituting the comparison circuit 2, the primary addition circuit 3 and the first and
second transmission path formation circuits 4 and 5, respectively. And to the delay circuit 8.
[0032]
Thereby, the primary addition circuit 3 adds the sound waves X1a (t) and X1b (t) that have
reached the first and second microphones 1a and 1b, and outputs the output wave Y1a (t) shown
in equation (3). It is generated and sent to the third-order addition circuit 9 and the second-order
04-05-2019
9
subtraction circuit 10, respectively.
Y1a (t) = X1a (t) + X1b (t) = sin ωt + sin ω (t−τ) (3)
[0033]
Here, the comparison circuit 2 compares the sound wave X1b (t) arriving at the second
microphone 1b with the phase that the sound wave X1a (t) arriving at the first microphone 1a is
advanced. The relays Ry constituting the first and second transmission path forming circuits 4
and 5 which detect based on the difference and receive the comparison result control the
changeover switches SW4 and SW5 of the own circuit to make the second make contact. P4b
closes the first make contact P5a.
[0034]
By this control, the transmission paths from secondary addition circuit 6 to tertiary addition
circuit 9 and secondary subtraction circuit 10 are cut off, while primary subtraction circuit 7 to
tertiary addition circuit 9 and secondary subtraction circuit 10, respectively. The transmission
path from the secondary subtraction circuit 10 to the output terminal 11 is cut off, while the
transmission path from the tertiary addition circuit 9 to the output terminal 11 is formed.
[0035]
Further, the comparison circuit 2 detects the time corresponding to the predetermined distance L
and the first incident angle φ1, that is, the time τ shown in the equation (1), and sends the
detection result to the delay circuit 8.
The delay circuit 8 receiving this detection result delays the sound wave X1b (t) arriving at the
second microphone 1b by time τ, and then sends it to the secondary addition circuit 6 and the
primary subtraction circuit 7, respectively.
[0036]
Thus, the output wave X1b (t−τ) sent to the secondary addition circuit 6 and the primary
subtraction circuit 7 can be expressed by equation (4).
04-05-2019
10
X1 b (t-τ) = sin ω (t-2 τ) (4)
[0037]
Of the primary subtraction circuit 7 and the tertiary addition circuit 9 provided on the
transmission path from the first and second microphones 1a and 1b to the output terminal 11 by
the above-described first operation, the primary subtraction circuit 7 The output wave Y1b (t)
shown in the equation (5) is generated by subtracting the output wave X1b (t-.tau.) From the
delay circuit 8 from the sound wave X1a (t) arriving at the microphone 1a of 1. And the
secondary subtraction circuit 10 respectively.
Y1b (t) = X1a (t) -X1b (t-τ) = sin ωt-sin ω (t-2τ) (5)
[0038]
On the other hand, the tertiary addition circuit 10 adds the output wave Y1a (t) from the primary
addition circuit 3 and the output wave Y1b (t) from the primary subtraction circuit 7 to the
output terminal 11 as shown in equation (6). The output wave Z1 (t) shown is to be transmitted.
Z1 (t) = Y1a (t) + Y1b (t) = 2 · sin ωt + sin ω (t−τ) −sin ω (t−2τ) (6)
[0039]
Next, as shown in FIG. 1B as the second operation, the first and second microphones 1a and 1b
disposed on the front side of the same plane and separated by a predetermined distance L For
example, when an acoustic wave having an acoustic velocity of 34000 cm / S [sec] arrives at an
incident angle of “90 ° <φ2 ≦ 180 °” at 2, the arrival time to the first microphone 1a
reaches the second microphone 1b. As compared with the time, the time τ [sec] shown in
equation (7) is delayed.
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τ = L · sin {φ2- (π / 2)} / 34000 (7)
[0040]
As a result, sound waves X2a (t) and X2b (t) that have reached the first and second microphones
1a and 1b can be expressed by equation (8).
X2a (t) = sin ω (t−τ) X2b (t) = sin ω (t) (8)
[0041]
Further, referring to FIG. 2B as the second operation, the sound wave X2a (t) that has reached
the first microphone 1a is transmitted to the comparison circuit 2, the primary addition circuit 3,
the first and second transmission paths. It is sent to the relay Ry constituting the forming circuits
4 and 5, the first secondary addition circuit 6 and the primary subtraction circuit 7, respectively.
On the other hand, the sound wave X2b (t) that has reached the second microphone 1b is sent
out to the relay Ry constituting the comparison circuit 2, the primary addition circuit 3 and the
first and second transmission path forming circuits 4 and 5, respectively. And to the delay circuit
8.
[0042]
Thereby, the primary addition circuit 3 adds the sound waves X2a (t) and X2b (t) that have
reached the first and second microphones 1a and 1b, and outputs the output wave Y2a (t) shown
in equation (9). It is generated and sent to the third-order addition circuit 9 and the second-order
subtraction circuit 10, respectively.
Y2a (t) = X2a (t) + X2b (t) = sin ω (t−τ) + sin ω (t) (9)
[0043]
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Here, the comparison circuit 2 compares the sound wave X2a (t) that has reached the first
microphone 1a with the phase that the sound wave X2b (t) that has reached the second
microphone 1b has advanced in amplitude. The relays Ry constituting the first and second
transmission path forming circuits 4 and 5 which detect based on the difference and receive the
comparison result control the changeover switches SW4 and SW5 of the own circuit to make the
first make contact. P4a and the second make contact P5b are closed respectively.
[0044]
By this control, the respective transmission paths from primary subtraction circuit 7 to tertiary
addition circuit 9 and secondary subtraction circuit 10 are cut off, while secondary addition
circuit 6 to tertiary addition circuit 9 and secondary subtraction circuit 10 are respectively cut
off. The transmission path from the third-order adder circuit 9 to the output terminal 11 is cut
off, while the transmission path from the second-order subtraction circuit 10 to the output
terminal 11 is formed.
[0045]
Further, the comparison circuit 2 detects the time corresponding to the predetermined distance L
and the second incident angle φ2, that is, the time τ shown in the equation (7), and sends the
detection result to the delay circuit 8.
The delay circuit 8 receiving this detection result delays the sound wave X2b (t) arriving at the
second microphone 1b by time τ, and sends it to the secondary addition circuit 6 and the
primary subtraction circuit 7, respectively.
[0046]
Thereby, the output wave X2b (t-τ) sent to the secondary addition circuit 6 and the primary
subtraction circuit 7 can be expressed by the equation (10).
X2b (t-τ) = sin ω (t-τ) (10)
[0047]
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The secondary addition circuit 6 of the secondary addition circuit 6 and the secondary
subtraction circuit 10 provided on the transmission path from the first and second microphones
1a and 1b to the output terminal 11 by the second operation described above Generates the
output wave Y2b (t) shown in equation (11) by adding the sound wave X2a (t) that has reached
the first microphone 1a and the output wave X2b (t-.tau.) From the delay circuit 8 The signal is
sent to the adding circuit 9 and the secondary subtracting circuit 10 respectively.
Y2b (t) = X2a (t) + X2b (t-τ) = 2 · sin ω (t-τ) (11)
[0048]
On the other hand, the secondary subtraction circuit 10 subtracts the output wave Y2b (t) from
the secondary addition circuit 6 from the output wave Y2a (t) from the primary addition circuit 3
so that the output terminal 11 receives The output wave Z2 (t) shown in) is sent out.
Z2 (t) = Y2a (t) -Y2b (t) = sin ωt-sin ω (t-τ) (12)
[0049]
Next, as shown in FIG. 1C as the third operation, the first and second microphones 1a and 1b
disposed on the front side of the same plane at a predetermined distance L apart are For
example, when an acoustic wave having an acoustic velocity of 34000 cm / S [sec] arrives at the
incident angle “180 ° <φ3 ≦ 270 °” of 3, the arrival time to the first microphone 1a
reaches the second microphone 1b. The time τ [sec] shown in equation (13) is delayed
compared to time.
τ = L · sin {(3π / 2) −φ3} / 34000 (13)
[0050]
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As a result, sound waves X3a (t) and X3b (t) that have reached the first and second microphones
1a and 1b can be expressed by equation (14). X3a (t) = sin ω (t−τ) X3b (t) = sin ω (t) (14)
[0051]
Further, referring to FIG. 2B as the third operation, the sound wave X3a (t) that has reached the
first microphone 1a is transmitted to the comparison circuit 2, the primary addition circuit 3, the
first and second transmission paths. The relays Ry constituting the forming circuits 4 and 5, the
secondary adding circuit 6 and the primary subtracting circuit 7 are respectively sent. On the
other hand, the sound wave X3b (t) that has reached the second microphone 1b is sent out to the
relay Ry constituting the comparison circuit 2, the primary addition circuit 3 and the first and
second transmission path forming circuits 4 and 5, respectively. And to the delay circuit 8.
[0052]
Thereby, the primary addition circuit 3 adds the sound waves X3a (t) and X3b (t) that have
reached the first and second microphones 1a and 1b, and outputs the output wave Y3a (t) shown
in equation (15). It is generated and sent to the third-order addition circuit 9 and the secondorder subtraction circuit 10, respectively. Y3a (t) = X3a (t) + X3b (t) = sin ω (t−τ) + sin ω (t)
(15)
[0053]
Here, the comparison circuit 2 compares the sound wave X3a (t) that has reached the first
microphone 1a with the phase that the sound wave X3b (t) that has reached the second
microphone 1b has advanced in amplitude. The relays Ry constituting the first and second
transmission path forming circuits 4 and 5 which detect based on the difference and receive the
comparison result control the changeover switches SW4 and SW5 of the own circuit to make the
first make contact. P4a and the second make contact P5b are closed respectively.
[0054]
By this control, the respective transmission paths from primary subtraction circuit 7 to tertiary
addition circuit 9 and secondary subtraction circuit 10 are cut off, while secondary addition
circuit 6 to tertiary addition circuit 9 and secondary subtraction circuit 10 are respectively cut
off. The transmission path from the third-order adder circuit 9 to the output terminal 11 is cut
off, while the transmission path from the second-order subtraction circuit 10 to the output
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terminal 11 is formed.
[0055]
Further, the comparison circuit 2 detects the time corresponding to the predetermined distance L
and the third incident angle φ3, that is, the time τ shown in the equation (13), and sends the
detection result to the delay circuit 8.
The delay circuit 8 receiving this detection result delays the sound wave X3b (t) arriving at the
second microphone 1b by time τ, and then sends it to the secondary addition circuit 6 and the
primary subtraction circuit 7, respectively.
[0056]
Thus, the output wave X3b (t-τ) sent to the secondary addition circuit 6 and the primary
subtraction circuit 7 can be expressed by equation (16).
X3b (t-τ) = sin ω (t-τ) (16)
[0057]
The secondary addition circuit 6 of the secondary addition circuit 6 and the secondary
subtraction circuit 10 provided on the transmission path from the first and second microphones
1a and 1b to the output terminal 11 by the third operation described above Generates the output
wave Y3b (t) shown in equation (17) by adding the sound wave X3a (t) that has reached the first
microphone 1a and the output wave X3b (t-.tau.) From the delay circuit 8 The signal is sent to
the adding circuit 9 and the secondary subtracting circuit 10 respectively. Y3b (t) = X3a (t) + X3b
(t-τ) = 2 · sin ω (t-τ) (17)
[0058]
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On the other hand, the secondary subtraction circuit 10 subtracts the output wave Y3b (t) from
the secondary addition circuit 6 from the output wave Y3a (t) from the primary addition circuit 3
so that the output terminal 11 receives The output wave Z3 (t) shown in) is sent out. Z3 (t) = Y3a
(t) -Y3b (t) = sin ωt-sin ω (t-τ) (18)
[0059]
Next, as shown in FIG. 1D as the fourth operation, the first and second microphones 1a and 1b
arranged at the predetermined distance L on the front side of the same plane are separated as
shown in FIG. For example, when an acoustic wave having an acoustic velocity of 34000 cm / S
[sec] arrives at an incident angle of “270 ° <φ4 ≦ 360 °” at 4, the arrival time to the
second microphone 1b reaches the first microphone 1a. The time τ [sec] shown in equation (19)
is delayed compared to time. τ = L · sin {φ 4- (3π / 2)} / 34000 (19)
[0060]
As a result, sound waves X4a (t) and X4b (t) that have reached the first and second microphones
1a and 1b can be expressed by equation (20). X4a (t) = sin ω (t) X4b (t) = sin ω (t−τ) (20)
[0061]
Further, referring to FIG. 2A as the fourth operation, the sound wave X4a (t) that has reached the
first microphone 1a is transmitted to the comparison circuit 2, the primary addition circuit 3, the
first and second transmission paths. The relays Ry constituting the forming circuits 4 and 5, the
secondary adding circuit 6 and the primary subtracting circuit 7 are respectively sent. On the
other hand, the sound wave X4b (t) arriving at the second microphone 1b is sent out to the relay
Ry constituting the comparison circuit 2, the primary addition circuit 3 and the first and second
transmission path formation circuits 4 and 5, respectively. And to the delay circuit 8.
[0062]
Thereby, the primary addition circuit 3 adds the sound waves X4a (t) and X4b (t) that have
reached the first and second microphones 1a and 1b, and outputs the output wave Y4a (t) shown
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in equation (21). It is generated and sent to the third-order addition circuit 9 and the secondorder subtraction circuit 10, respectively. Y4a (t) = X4a (t) + X4b (t) = sin ωt + sin ω (t−τ) (21)
[0063]
Here, the comparison circuit 2 compares the sound wave X4b (t) arriving at the second
microphone 1b with the phase that the sound wave X4a (t) arriving at the first microphone 1a is
advanced. The relays Ry constituting the first and second transmission path forming circuits 4
and 5 which detect based on the difference and receive the comparison result control the
changeover switches SW4 and SW5 of the own circuit to make the second make contact. P4b
closes the first make contact P5a.
[0064]
By this control, the transmission paths from secondary addition circuit 6 to tertiary addition
circuit 9 and secondary subtraction circuit 10 are cut off, while primary subtraction circuit 7 to
tertiary addition circuit 9 and secondary subtraction circuit 10, respectively. The transmission
path from the secondary subtraction circuit 10 to the output terminal 11 is cut off, while the
transmission path from the tertiary addition circuit 9 to the output terminal 11 is formed.
[0065]
Further, the comparison circuit 2 detects the time corresponding to the predetermined distance L
and the fourth incident angle φ4, that is, the time τ shown in the equation (19), and sends the
detection result to the delay circuit 8.
The delay circuit 8 receiving this detection result delays the sound wave X4b (t) arriving at the
second microphone 1b by time τ, and then sends it to the secondary addition circuit 6 and the
primary subtraction circuit 7, respectively.
[0066]
Thus, the output wave X4b (t-τ) sent to the secondary addition circuit 6 and the primary
subtraction circuit 7 can be expressed by equation (22).
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X4b (t-τ) = sin ω (t-2τ) (22)
[0067]
Of the primary subtraction circuit 7 and the tertiary addition circuit 9 provided on the
transmission path from the first and second microphones 1a and 1b to the output terminal 11 by
the above-described fourth operation, the primary subtraction circuit 7 The output wave Y4b (t)
shown in equation (23) is generated by subtracting the output wave X4b (t-.tau.) From the delay
circuit 8 from the sound wave X4a (t) that has reached the microphone 1a of 1. And the
secondary subtraction circuit 10 respectively. Y4b (t) = X4a (t)-X4b (t-τ) = sin ωt-sin ω (t-2τ)
(23)
[0068]
On the other hand, the tertiary addition circuit 10 adds the output wave Y4a (t) from the primary
addition circuit 3 and the output wave Y4b (t) from the primary subtraction circuit 7 to the
output terminal 11 as shown in equation (24). The output wave Z4 (t) shown is to be transmitted.
Z4 (t) = Y4a (t) + Y4b (t) = 2 · sin ωt + sin ω (t−τ) −sin ω (t−2τ) (24)
[0069]
The output waves Z1 (t) and Z2 (t) shown in the equations (6), (12), (18) and (24), respectively,
which are sent to the output terminal 11 by the first to fourth operations described above When
calculating the values of Z.sub.1 (Z), Z.sub.3 (t), Z.sub.4 (t), predetermined intervals L of the first
and second microphones 1a and 1b spaced apart on the front side of the same plane are set as 1.
When the frequency of the sound source is fixed as 0 [cm], the frequency of the sound source is
varied as F1 = 300, F2 = 1000, F3 = 2000, F4 = 3000, F5 = 5000, F6 = 7000, F7 = 10000 [Hz].
As shown in the directivity characteristic diagram of FIG. 3A, it is possible to obtain a rotational
curved directivity characteristic of a fan-shaped section in the front side direction of the plane.
[0070]
Similarly, the output waves Z1 (t) and Z2 (t) shown in the equations (6), (12), (18) and (24),
respectively, which are sent to the output terminal 11 by the first to fourth operations. In the
case of fixing the frequency of the sound source as F = 1000 [Hz] in calculating the values of Z1),
Z3 (t), and Z4 (t), the first, When the predetermined intervals of the second microphones 1a and
1b are changed as L1 = 1.0, L2 = 2.0, L3 = 3.0, L4 = 4.0 [cm], as shown in FIG. As shown in the
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directivity characteristic diagram of (4), it is possible to obtain a rotating curved surface
directivity characteristic of a fan-shaped section in the front side direction of the plane.
[0071]
Thereby, for example, a pair of microphones 1a and 1b and a speaker (not shown) on the front
side of the same plane of one case such as an intercom device.
Even in the case of the above-mentioned arrangement, it is possible to realize a simultaneous
voice call with enhanced sound characteristics.
[0072]
Although the microphone device of the present invention has been described with reference to a
specific embodiment, the present invention is not limited to this embodiment, and any device
having any configuration heretofore known can be used as long as the effects of the present
invention can be obtained. It is needless to say that can be adopted.
[0073]
1a, 1b ··· First and second microphones (pair of microphones) 2 ··· Comparison circuit
(comparison means) 3 ··· Primary addition circuit (first operation means) 4 · Ry, SW 4 ··· First
Transmission path formation circuit (first transmission path formation means) 5, Ry, SW5 ...
second transmission path formation circuit (second transmission path formation means) 6 ...
secondary addition circuit (second arithmetic means) 7 ... primary subtraction circuit (second
operation means) 8 ... delay circuit (delay means) 9 ... tertiary addition circuit (third operation
means) 10 ... secondary subtraction circuit (third operation means) 11 ...... Output terminal
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