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JPH06303691

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DESCRIPTION JPH06303691
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
stereo microphone for collecting a distant sound in stereo with high S / N.
[0002]
2. Description of the Related Art A conventional stereo microphone will be described below.
[0003]
FIG. 7 shows the configuration of a conventional stereo microphone.
60 is a first directional microphone unit, 61 is a second directional microphone unit, and the
main axis of the first directional microphone unit is directed in the direction of an angle θ from
the front direction to the left, and the second directional microphone unit is The main axis of the
sexual microphone unit is directed in the direction of the angle θ from the front direction to the
right. Reference numeral 62 denotes a first output terminal, which receives an output signal from
the first directional microphone unit. Reference numeral 63 denotes a second output terminal,
which receives an output signal from the second directional microphone unit.
[0004]
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The operation of the conventional stereo microphone configured as described above will be
described below.
[0005]
The first directional microphone unit 60 whose directivity main axis is directed in the direction of
the angle θ from the front direction to the left side emphasizes the sound on the left side and
picks up the directivity characteristics as shown in FIG. 7B. obtain.
Further, the second directional microphone unit 61 whose directivity main axis is directed in the
direction of the angle θ from the front direction to the right side emphasizes and collects the
sound on the right side, as shown in FIG. 7C. Get the characteristics. Thereby, stereo sound
collection is realized. At this time, the range of θ is usually set to 45 ° ≦ θ ≦ 90 °.
[0006]
SUMMARY OF THE INVENTION However, in the above configuration, the sound collection angle
is wide because the purpose is to obtain a stereo feeling of the nearby sound field, and a wide
range sound is collected, so a superdirectional microphone is used. It has the problem that it is
not possible to pick up distant sounds that can be picked up, and even if the surroundings are
quiet and it is possible to pick up distant sounds, it is not possible to obtain a stereo feeling of a
distant sound field .
[0007]
The present invention solves the above-mentioned problems, and provides a stereo microphone
which distributes the directivity characteristic of superdirectivity to right and left and collects
distant sounds in stereo.
[0008]
In order to achieve the above object, according to the stereo microphone of the present
invention, the first superdirective microphone and the second superdirective microphone are
provided parallel to each other with their main axes directed in the front direction. A first signal
delaying means provided downstream of the first superdirective microphone, a second signal
delaying means provided downstream of the second superdirective microphone, and a first
superdirective microphone First signal subtracting means which receives the output signal from
the second signal delay means and the output signal from the second signal delay means, the
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output signal from the second superdirective microphone and the output signal from the first
signal delay means By obtaining an output signal from each of the first signal subtracting means
and the second signal subtracting means, a microphone having superdirectivity and capable of
stereo sound collection can be obtained.
[0009]
Further, by making the signal delay amounts of the first signal delay means and the second signal
delay means variable, it is possible to adjust the sense of stereo according to the sound field.
The range of the signal delay amount τ1 at this time is 0 <τ1 ≦ d / c, where d is the distance
between the sound holes of the first superdirective microphone and the second superdirective
microphone and c is the speed of sound. is there.
[0010]
Furthermore, the first superdirective microphone and the second superdirective microphone are
waveform-type superdirective microphones provided with sound holes on the side of the acoustic
tube, and the sound holes of the first superdirective microphone and By providing in opposite
directions so that the distance between the sound holes of the second superdirective microphone
is maximized, the distance between the sound holes can be increased within a limited size, and
Characteristics can be improved.
[0011]
Furthermore, a first superdirective microphone and a second superdirective microphone face
main axes in the front direction and are disposed parallel to each other, and a first signal delay
that receives an output signal from the first superdirective microphone as an input Means, a
second signal delay means for receiving an output signal from the second superdirective
microphone, a third signal delay means for receiving an output signal from the first
superdirective microphone, A fourth signal delay unit receiving an output signal from the two
superdirective microphones, a first amplitude phase correction unit receiving the output signal
from the first signal delay unit, and a second signal delay unit A second amplitude / phase
correction unit receiving the output signal from the unit; and a first signal subtraction unit
receiving the output signal from the third signal delay unit and the output signal from the second
amplitude / phase correction unit And fourth signal delay means And second signal subtracting
means for receiving the output signal from the first amplitude phase correction means and the
first output signal from the first amplitude phase correction means, and correcting the variation
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in the characteristics of the first and second superdirective microphones. In the part of the first
and second signal subtraction means, subtraction of the signal from the specific direction is
surely performed, and directivity can be improved.
[0012]
Furthermore, in addition to the above configuration, the first amplitude phase correction means
is provided with a cross correlation operation means that receives an output signal from the first
superdirective microphone and an output signal from the second superdirective microphone. The
first adaptive amplitude phase correction means is exchanged, and the amplitude phase
characteristic thereof is updated based on the output signal from the second signal subtraction
means and the output signal from the cross correlation calculation means, and the second
amplitude phase correction means By replacing the first adaptive amplitude and phase correction
means with the amplitude and phase characteristics being updated based on the output signal
from the first signal subtraction means and the output signal from the cross correlation
calculation means. The first adaptive amplitude phase correction means and the second adaptive
amplitude phase correction means can realize appropriate characteristics by self-learning.
[0013]
[Operation] The stereo microphone configured as described above is the sound collected by the
first superdirective microphone installed on the right side with respect to the front direction and
the second superdirective microphone installed on the left side. A signal is calculated and
separated into left and right signals.
It is assumed that the characteristics of the first and second superdirective microphones are
approximately equal.
The first signal subtraction means subtracts the output signal from the first superdirective
microphone and the output signal from the second superdirective microphone delayed by time
.tau.1, and as a result of the subtraction, the front surface is obtained. Cancellation of the signal
in the direction of the angle θ = sin -1 (τ1 · c / d) is performed from the direction to the left
(where d is the distance between the sound holes of the first and second superdirective
microphones, c is the speed of sound ).
Therefore, the output from the first signal subtraction means is a directivity characteristic in
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which a dead angle is formed in the direction of the angle θ on the left of the directivity
characteristic of the first superdirective microphone, and a superdirective that takes sound from
the front to the right It becomes a characteristic.
[0014]
Similarly, the second signal subtraction means subtracts the output signal from the second
superdirective microphone and the output signal from the first superdirective microphone
delayed by time .tau.1, and as a result, The output of the second signal subtraction means is a
directional characteristic in which a dead angle is formed in the direction of the angle θ to the
right of the directional characteristic of the second superdirective microphone, that is, Become.
At this time, the value of .tau.1 is 0 <.tau.1.ltoreq.d / c, where 0 <.theta..ltoreq.90.degree.
The angles .theta. And .tau.1 from the front of the dead angle direction are given by (Equation 1).
[0016]
Further, by making τ 1 variable, it is possible to change the angle in the dead angle direction so
that the directivity setting according to the sound field and the condition of the hollow of the
sound in the front direction can be adjusted. Become.
[0017]
Furthermore, the third and fourth signal delay means and the first and second amplitude phase
correction means are provided in the above-described configuration, and the transfer
characteristic of the first amplitude and phase correction means is H1 (ω), the second amplitude
phase Assuming that the transfer characteristic of the correction means is H2 (ω), each
characteristic is determined by (Equation 2) and (Equation 3).
[0020]
Where M1R (ω) and M2R (ω) are the frequency characteristics of the first and second
superdirective microphones in the right θ ° direction, and M1L (ω) and M2L (ω) are the first
frequency characteristics in the left θ ° direction 1 is a frequency characteristic of a second
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superdirective microphone.
If the characteristics of the first and second superdirective microphones are exactly the same,
M1R (.omega.) = M2R (.omega.), M1L (.omega.) = M2L (.omega.), But in practice the individual
superdirective microphones The first and second amplitude phase correction means are provided
for the purpose of matching the characteristics in the dead angle direction.
[0021] Further, the third and fourth signal delaying means are provided for the purpose of
compensating for the delay of the signal in the first and second amplitude and phase correcting
means. In this way, directivity is improved by more accurate cancellation of the blind spot signal.
[0022] Further, the cross correlation calculation means is provided as described above, and the
transfer characteristic H1 (ω) of the first adaptive amplitude phase correction means is
generated from the second signal subtraction means only when the correlation of the sound
wave from the right θ ° is high. The output signal from the second signal subtracting means is
used for updating so that the output signal from the second signal is reduced. Similarly, the
transfer characteristic H2 (ω) of the second adaptive amplitude phase correction means is the
output signal from the first signal subtraction means only when the correlation of the sound
wave from the left θ ° is high in the calculation result of the cross correlation calculation
means Update is performed using the output signal from the first signal subtraction means so as
to be smaller. By such operation, the first and second superdirective microphones are selfcorrected by the first and second adaptive amplitude and phase correction means in the dead
angle direction of the directivity (right and left directions θ ° respectively). Therefore, it is not
necessary to obtain M1R (ω), M2R (ω), M1L (ω), M2L (ω) by anechoic chamber measurement
etc., and even when the dead angle direction is changed by changing τ1 Appropriate H1 (ω)
and H2 (ω) are obtained.
[0023] As described above, the output of the first signal subtraction means is a superdirective
characteristic that picks up the right side from the front, and the output of the second signal
subtraction means is a superdirective characteristic that picks up the left side from the front .
[0024] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A stereo microphone
according to a first embodiment of the present invention will be described below with reference
to the drawings.
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[0025] FIG. 1 shows the configuration of a stereo microphone according to a first embodiment of
the present invention. In FIG. 1, 1 is a first superdirective microphone, 2 is a second
superdirective microphone, and a first superdirective microphone on the left side of the first
superdirective microphone with respect to the front, Install parallel and equidistant from the
front sound source. A first signal delay unit 11 receives an output signal from the first
superdirective microphone 1 as an input. A second signal delay unit 12 receives an output signal
from the second superdirective microphone 2 as an input. A first signal subtracting means 31
receives an output signal from the first superdirective microphone 1 and an output signal from
the second signal delay means 12 as input. The second signal subtracting means 32 receives the
output signal from the second superdirective microphone 2 and the output signal from the first
signal delay means 11 as input. Reference numeral 51 denotes a first output terminal, which is
provided downstream of the first signal subtracting means 31. Reference numeral 52 denotes a
second output terminal, which is provided downstream of the second signal subtracting means
32.
[0026] The operation of the stereo microphone configured as described above will be described
below with reference to FIGS. 1, 2 and 3.
[0027] In FIG. 1, it is assumed that the directivity characteristics of the first superdirective
microphone 1 and the second superdirective microphone 2 are substantially the same
characteristics as shown in FIG. 3 (a). The first signal subtraction means 31 subtracts the output
signal of the first superdirective microphone 1 and the output signal of the second superdirective
microphone 2 delayed by time τ1. As a result, the directivity characteristic of the output signal
from the first signal subtracting means 31 is such that a dead angle is formed in the direction of
the left θ ° of the superdirective characteristic of FIG. 3A. The angle θ is expressed by
Equation 4 when the distance between the sound holes of the first superdirective microphone 1
and the second superdirective microphone 2 is d and the speed of sound is c.
[0029] Further, when the relationship between θ, d, τ 1 and c is shown in FIG. 2, the sound
wave arriving from the front to the left from the direction of the angle θ ° first reaches the
second superdirective microphone 2 and time The first superdirective microphone 1 is reached
with a delay of d · cos (θ) / c. Therefore, the output signal from the second superdirective
microphone 2 is delayed by the second signal delay means 12 at time τ1 = d · cos (θ) / c, and
from the output signal of the first superdirective microphone 1 By pulling, the sensitivity to the
θ ° direction is made zero from the front to the left. This is a method of forming directivity of a
so-called sound pressure gradient microphone, and the directivity added by this calculation is as
shown in FIG. 3 (b). Therefore, the directivity characteristic of the output signal from the first
signal computing means 31 is as shown in FIG. 3 (c) in which the superdirectivity of FIG. 3 (a) is
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multiplied by the directivity of FIG. 3 (b). Similarly, the output signal from the second signal
subtraction means 32 has a superdirective characteristic (FIG. 3 (e)) having a dead angle in the
direction of the right angle θ °. A distant sound can be collected in stereo by directivity as
shown in FIG. 3 (c) (e).
[0030] In addition, in order to miniaturize the entire apparatus by arranging the first and second
superdirective microphones 1 and 2 as close as possible, as shown in FIG. 4A, the first
superdirective microphone 1 is provided. The second superdirective microphone 2 is a line
microphone (waveform microphone) provided with a sound hole on the side surface of the
acoustic tube, and the sound holes of the first and second superdirective microphones 1 and 2
are followed. The distance d is increased by arranging the sound hole on the side opposite to the
other superdirective microphone (Fig. 4 (a)), rather than arranging it so as to face (Fig. 4 (b)) The
characteristics of the bass range are improved (equal to the relationship between the distance
between the sound holes of the sound pressure gradient microphone (or between the
microphone elements) and the bass characteristics).
[0031] Further, by making the signal delay amounts .tau.1 of the first and second signal delay
means variable, it is possible to vary the angle .theta. In the dead angle direction according to the
above (Equation 5). Further, the range of .tau.1 at this time is 0 <.tau.1.ltoreq.d / c, considering
the range of .theta. As an appropriate value of 0.degree. <. Theta..ltoreq.90.
[0032] Hereinafter, a stereo microphone according to a second embodiment of the present
invention will be described with reference to the drawings.
[0033] FIG. 5 shows the configuration of a stereo microphone according to a second embodiment
of the present invention. In FIG. 5, 1 is a first superdirective microphone. 2 is a second
superdirective microphone. A first signal delay unit 11 receives an output signal from the first
superdirective microphone 1 as an input. A second signal delay unit 12 receives an output signal
from the second superdirective microphone 2 as an input. A third signal delay unit 13 receives
an output signal from the first superdirective microphone 1 as an input. A fourth signal delay
unit 14 receives an output signal from the second superdirective microphone 2 as an input.
Reference numeral 21 denotes a first amplitude / phase correction unit, which receives an output
signal from the first signal delay unit 11. The second amplitude / phase correction means 22
receives an output signal from the second signal delay means 12 as an input. The first signal
subtracting means 31 receives the output signal from the third signal delaying means 13 and the
output signal from the second amplitude / phase correcting means 22 as input. A second signal
subtracting means 32 receives the output signal from the fourth signal delay means 14 and the
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output signal from the first amplitude / phase correcting means 21 as input. Reference numeral
51 denotes a first output terminal, which is provided after the first signal subtracting means.
Reference numeral 52 denotes a second output terminal, which is provided after the second
signal subtracting means.
[0034] The operation of the stereo microphone configured as described above will be described
below with reference to FIG.
[0035] The third embodiment differs from the first embodiment in that the third signal delay
means 13 is provided between the first superdirective microphone 1 and the first signal
subtraction means 31 in FIG. The signal delay means 14 is provided between the second
superdirective microphone 2 and the second signal subtraction means 32, and the first amplitude
and phase correction means 21 is comprised of the first signal delay means 11 and the second
signal delay means 11. The second amplitude phase correction means 22 is provided between
the second signal delay means 12 and the first signal subtraction means 31. The purpose is to
match the amplitude phase characteristics of the first and second superdirective microphones 1
and 2 with respect to the left and right angle θ directions, and It is about making cancellation
enough. With regard to the determination of the transfer characteristics of the first and second
amplitude and phase correction means 21 and 22, the sound pressure frequency characteristics
in the right θ ° direction of the first and second superdirective microphones 1 and 2 measured
under the same conditions, respectively The transfer characteristic H1 (.omega.) Of the first
amplitude and phase correction means 21 is determined as M1R (.omega.) And M2R (.omega.) As
in Eq.
[0037] The output to the sound wave from the direction of the angle θ ° to the right of the first
superdirective microphone 1 is delayed by time τ 1 by the first signal delay means 11 and then
the first amplitude phase correction means 21 is equalized to the sound pressure frequency
characteristic for the sound wave from the direction of the right θ ° of the second
superdirective microphone 2, and the second signal subtraction means 32 The signal of the
sound wave in the direction of the right θ ° is canceled. At this time, the fourth signal delay
means 14 is provided in the first amplitude and phase correction means 21 for compensation
when a time delay of a signal occurs. Similarly, the transfer function of the second amplitude and
phase correction means 22 is determined as in (Equation 6).
[0039] The output to the sound wave from the direction of the angle θ ° at the left of the
second superdirective microphone 2 is delayed by time τ 1 by the second signal delay means 12
and then the second amplitude phase correction means The characteristics expressed in Eq. 6 are
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multiplied by 22 and equalized to the sound pressure frequency characteristics for the sound
wave from the left θ ° direction of the first superdirective microphone 1, and subtraction is
performed by the first signal subtraction means 31. And the sound wave signal in the left θ °
direction is canceled. At this time, the third signal delay means 13 is provided in the second
amplitude / phase correction means 22 for compensation when a time delay of a signal occurs.
[0040] As described above, in the second embodiment, even when the first and second
superdirective microphones 1 and 2 have slight characteristic variations, at least the formation of
the dead angle in the direction of the angle θ ° is sufficient at the left and right. To be done.
[0041] Hereinafter, a stereo microphone according to a third embodiment of the present
invention will be described with reference to the drawings.
[0042] FIG. 6 shows the configuration of the stereo microphone in the third embodiment of the
present invention. In FIG. 6, a first superdirective microphone 1, a second superdirective
microphone 2, a first signal delay means 11, a second signal delay means 12, a third signal delay
means 13, a fourth signal The delay means 14, the first signal subtraction means 31, the second
signal subtraction means 32, the first output terminal 51, and the second output terminal 52
have the same configuration as that of the second embodiment described above.
[0043] Points different from the second embodiment will be described below. First, reference
numeral 40 denotes a cross-correlation calculation unit, which receives output signals from the
first superdirective microphone 1 and the second superdirective microphone 2. A first adaptive
amplitude phase correction means 23 is replaced with the amplitude phase correction means 21
in the second embodiment, and receives an output signal from the first signal delay means 11 as
an input, and a second signal subtraction means A signal is output to 32. Further, the output
signal from the second signal subtracting means 32 and the output signal from the cross
correlation calculating means 40 are used as inputs to adaptively update its own transfer
characteristics. The second adaptive amplitude and phase correction means 24 is replaced with
the amplitude and phase correction means 22 in the second embodiment, and receives the
output signal from the second signal delay means 12 as an input, and the first signal subtraction
means A signal is output to 31. Further, the output signal from the first signal subtracting means
31 and the output signal from the cross correlation calculating means 40 are used as inputs to
adaptively update its own transfer characteristics.
[0044] The operation of the stereo microphone configured as described above will be described
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below with reference to FIG.
[0045] In FIG. 6, the operation different from that of the second embodiment is that the first and
second adaptive amplitude and phase correction means 23 and 24 have first and second
superdirectivities with respect to sound waves from dead angle directions of left and right θ °.
This is a point of adaptively equalizing the variation of the characteristics of the microphones 1
and 2. Here, as a specific example for realizing the first and second adaptive amplitude phase
correction means 23, 24, a normalized LMS algorithm (learning identification method) (for
example, S.I. Heikin, Takebe, M. Translation: "Introduction to Adaptive Filters", pp. 119 to 122) is
applied to the case of applying an adaptive equalizer.
[0046] The impulse response (filter coefficient) giving the transfer characteristic of the first
adaptive amplitude phase correction means 23 is hL (n), the output signal from the first signal
delay means 11 uL (n), the fourth signal delay means 14 The learning identification method is
expressed as in Eq. 7 and Eq. 8 where dL (n) is the output signal from the second and eL (n) is
the output signal from the second signal subtraction means 32, and In the adaptive amplitude
phase correction means 23, the updating of the filter coefficient of (Equation 7) and the
calculation of the second term of the right side of (Equation 8) are performed. (Math 8) The
minus on the right side corresponds to the second signal subtraction means 32. Also, when dL (n)
and uL (n) are independent of each other, Eq. 7 can not converge, so the sound wave strength
from the direction to be canceled is strong for normal operation as an equalizer. Only when
(Equation 7) the filter coefficients need to be updated. Therefore, the cross correlation calculation
means 40 sends a signal to the first adaptive amplitude phase correction means 23 indicating
whether the correlation of the sound wave in the direction of the angle θ ° is high to the right,
and updating of Eq. I do. The fourth signal delaying means 14 is provided to satisfy the causality
of time of each signal, and sets a time delay .tau.2 corresponding to the time length of the filter
impulse response hL (n). With such a configuration, the filter coefficient hL (n) is set so that uL
(n) matches dL (n) and eL (n) approaches zero for sound waves from the direction of angle θ °
from the front to the right. Is updated, and a clear blind spot is produced in the right θ °
direction.
[0049] The impulse response (filter coefficient) for giving the transfer characteristic of the
second adaptive amplitude and phase correction means 24 is hR (n), the output signal from the
second signal delay means 12 is uR (n), the third signal Assuming that the output signal from the
delay means 13 is dR (n) and the output signal from the first signal subtraction means 31 is eR
(n), the learning identification method is expressed as in Eq. 9 and Eq. 10 In the second adaptive
amplitude phase correction means 24, the updating of the filter coefficient of (Equation 9) and
the calculation of the second term of the right side of (Equation 10) are performed.
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[0050] (Math 10) The minus on the right side corresponds to the first signal subtracting means
31. Also, when dR (n) and uR (n) are independent of each other, Eq. 9 can not converge, so the
sound wave strength from the direction to be canceled is strong for normal operation as an
equalizer. Only when (Equation 7) the filter coefficients need to be updated. Therefore, the crosscorrelation calculation means 40 sends a signal to the second adaptive amplitude phase
correction means 24 indicating whether the correlation of the sound wave in the direction of the
angle θ ° is high to the left, and updating of Eq. I do. The third signal delay means 13 is
provided to satisfy the causality of the time of each signal, and sets a time delay .tau.2
corresponding to the time length of the filter impulse response hR (n). With such a configuration,
the filter coefficient hR (n) is set so that uR (n) matches dR (n) and eR (n) approaches zero with
respect to sound waves from the direction of angle θ ° from the front to the left. Is updated,
and a clear blind spot is produced in the left θ ° direction.
[0051] Where hL (n) and hR (n) are vectors indicating a filter coefficient sequence at time n, and
uL (n) and uR (n) are tap input vectors (uL (n) = {uL (n), uL (n−1), uL (n−2),.
[0054] According to the present invention, the first superdirective microphone and the second
superdirective microphone are provided parallel to each other with their main axes facing in the
front direction, and provided at the rear stage of the first superdirective microphone. A first
signal delaying means, a second signal delaying means provided downstream of the second
superdirective microphone, an output signal from the first superdirective microphone, and an
output from the second signal delaying means A first signal subtracting unit that receives a
signal, and a second signal subtracting unit that receives an output signal from the second
superdirective microphone and an output signal from the first signal delay unit; By obtaining an
output signal from each of the signal subtraction means and the second signal subtraction means
of the above, it is possible to realize a stereo microphone which distributes the directivity of
superdirectivity to the left and right, and collects distant sounds in stereo.
[0055] Further, by making the signal delay amounts of the first signal delay means and the
second signal delay means variable, it is possible to adjust the sense of stereo according to the
sound field. The range of the signal delay amount .tau.1 at this time is 0 <.tau.1.ltoreq.d / c,
where d is the distance between the sound holes of the first superdirective microphone and the
second superdirective microphone and c is the speed of sound. .
[0056] Furthermore, the first superdirective microphone and the second superdirective
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microphone are waveform-type superdirective microphones provided with sound holes on the
side surface of the acoustic tube, and the first superdirective microphone and the second
superdirective microphone. By providing the sound holes of the superdirective microphone in
opposite directions so as to maximize the distance between the sound holes, it is possible to
increase the distance between the sound holes within a limited size, and the characteristics of the
bass range Can improve.
[0057] Furthermore, a first superdirective microphone and a second superdirective microphone
face main axes in the front direction and are disposed parallel to each other, and a first signal
delay that receives an output signal from the first superdirective microphone as an input Means,
a second signal delay means for receiving an output signal from the second superdirective
microphone, a third signal delay means for receiving an output signal from the first
superdirective microphone, A fourth signal delay unit receiving an output signal from the two
superdirective microphones, a first amplitude phase correction unit receiving the output signal
from the first signal delay unit, and a second signal delay unit A second amplitude / phase
correction unit receiving the output signal from the unit; and a first signal subtraction unit
receiving the output signal from the third signal delay unit and the output signal from the second
amplitude / phase correction unit And fourth signal delay means And second signal subtracting
means for receiving the output signal from the first amplitude phase correction means and the
first output signal from the first amplitude phase correction means, and correcting the variation
in the characteristics of the first and second superdirective microphones. In the part of the first
and second signal subtraction means, subtraction of the signal from the specific direction is
surely performed, and directivity can be improved.
[0058] Furthermore, in addition to the above configuration, the first amplitude phase correction
means is provided with a cross correlation operation means that receives an output signal from
the first superdirective microphone and an output signal from the second superdirective
microphone. The first adaptive amplitude phase correction means is exchanged, and the
amplitude phase characteristic thereof is updated based on the output signal from the second
signal subtraction means and the output signal from the cross correlation calculation means, and
the second amplitude phase correction means By replacing the first adaptive amplitude and
phase correction means with the amplitude and phase characteristics being updated based on the
output signal from the first signal subtraction means and the output signal from the cross
correlation calculation means. The first adaptive amplitude phase correction means and the
second adaptive amplitude phase correction means can realize appropriate characteristics by
self-learning.
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