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JP2017152895

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DESCRIPTION JP2017152895
Abstract: The present invention provides an acoustic sensor and a sound wave detection method
that reduce noise regardless of the frequency of a sound wave to be detected and suppress the
reduction in sensitivity and the occurrence of directivity disturbance. An acoustic sensor 10 is
disposed at intervals along a detection direction, and three or more detection elements E0 to E3
each detecting an acoustic wave signal including a component of an acoustic wave, and
arithmetic processing on each acoustic wave signal And an arithmetic processing unit 30 for
detecting a sound wave. The arithmetic processing unit corresponds to each of the plurality of
subtractors 40A to 40C for performing subtraction processing on each of two sound wave
signals corresponding to adjacent detection elements, and for each of the sound wave signals
subjected to subtraction processing, the sound wave signals. It has a subtraction side delay
device 51 which applies a delay according to the position of the detection element, and a
reduction value adder 62 which performs addition processing on the output from the subtraction
side delay device. [Selected figure] Figure 1
Acoustic sensor and sound wave detection method
[0001]
The present invention relates to an acoustic sensor and a sound wave detection method.
[0002]
Patent Document 1 discloses an example of an acoustic sensor that detects an acoustic wave in
water.
05-05-2019
1
The acoustic sensor of Patent Document 1 uses two detection elements that detect an acoustic
wave signal containing a component of the acoustic wave, has high sensitivity to the acoustic
wave propagating from the detection direction, and propagates from the direction opposite to the
detection direction. The incoming sound wave is given directivity with low sensitivity.
[0003]
Patent Document 2 discloses an example of a detection element. The detection element of Patent
Document 2 has a structure in which an elastic body is inserted in an optical fiber coil, and phase
modulation of light is performed by utilizing distortion of the optical fiber due to sound waves. A
signal detected by such a detection element can be demodulated using a demodulator shown in
Non-Patent Document 1 or the like.
[0004]
FIG. 7 is a schematic view showing the configuration of an acoustic sensor according to the prior
art. FIG. 7 shows an optical fiber acoustic sensor that detects an acoustic wave in water with an
optical fiber as an acoustic sensor 100 that can be realized by the prior art disclosed in the
above-mentioned documents. The acoustic sensor 100 has a detection element F and a detection
element B that modulate the light emitted by the light source / demodulator 200 with a sound
wave signal. The detection element F and the detection element B are disposed at an interval d
along the detection direction, and the detection element F is disposed on the detection direction
side of the detection element B. The light source / demodulator 200 demodulates the light
modulated by the detection element F to generate a sound wave signal p F, and demodulates the
light modulated by the detection element B to generate a sound wave signal p B.
[0005]
Then, based on the sound wave signal p F and the sound wave signal p B generated by the light
source / demodulator 200, the acoustic sensor 100 includes a signal adder 610, a subtractor
400, an integration / amplifier 700, and an output adder 630. The following equation (1) is
calculated using the equation (1) to obtain an output V which is information of a sound wave.
[0006]
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2
[0007]
Here, t is time and c is the speed of sound.
When a sine wave of amplitude P and angular frequency ω propagating from an angle of θ with
respect to the detection direction is detected, p F, p B and V are respectively given by the
following formulas (2) to (4) Is represented by
[0008]
[0009]
[0010]
[0011]
Here, k is a wave number.
The normalized sensitivity D in the equation (4) is expressed by the following equation (5).
[0012]
[0013]
FIG. 8 is a graph showing the calculation results of the normalized sensitivity D with respect to
the product kd of the wave number k and the distance d between two detection elements.
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3
FIG. 8 shows how the normalized sensitivity D changes in accordance with kd for two ways of θ
= 0 and θ = π (rad).
It can be seen from FIG. 8 that in the range of kd <1, the sensitivity is high when θ = 0 and the
sensitivity is low when θ = π (rad).
[0014]
JP 2007-12024 JP JP 2012-68087 JP
[0015]
JASA Vol.
115, No. 6 “Acoustic Performance of a large-aperture, seabed, fiber-optic hydrophone array”
[0016]
However, in the conventional acoustic sensor 100, noise is generated due to fluctuations in the
wavelength of the light source.
That is, in general, the noise component of the sound wave signal corresponding to the two
detection elements has many uncorrelated components, so the noise level does not decrease in
the subtraction of the two items of the above equation (1).
On the other hand, since there is a correlation between the sound wave components of the sound
wave signal corresponding to the two detection elements, the signal level becomes low in the
subtraction of the two items of the above equation (1). Moreover, since the correlation of the
component of a sound wave is so large that the frequency of the sound wave to detect is low,
when detecting a low sound wave, the signal level in the said subtraction falls further largely.
[0017]
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4
FIG. 9 is a graph showing the gain of the integration process with respect to the product kd of
the wave number k and the distance d between two detection elements. As kd is proportional to
the frequency, it can be seen from FIG. 9 that the lower the frequency of the sound wave to be
detected, the larger the gain. Therefore, in the processing by the conventional acoustic sensor
100, the lower the frequency of the sound wave to be detected, the larger the noise of the output,
and the more difficult the detection of the signal indicating the weak sound wave.
[0018]
In the conventional acoustic sensor 100, if the distance d is increased, the gain of the integration
/ amplifier 700 can be lowered, so that part of the noise can be suppressed. However, when the
distance d is increased, the upper limit of the frequency range in which kd <1 is lowered, so that
the sensitivity is lowered and the directivity is disturbed when detecting the sound wave of high
frequency. Furthermore, even in the case of an acoustic sensor having a detection element using
a piezoelectric material, the noise generated by the amplifier lowers the signal level of the sound
wave to be detected as in the case of the optical fiber acoustic sensor, thereby lowering the
sensitivity and directivity. Disturbance occurs. Therefore, regardless of the frequency of the
sound wave to be detected, an acoustic sensor and a sound wave detection method are desired
which reduce noise and suppress the decrease in sensitivity and the occurrence of disturbance in
directivity.
[0019]
The acoustic sensor according to the present invention is disposed at intervals along the
detection direction, and is detected by three or more detection elements each detecting an
acoustic signal including an acoustic wave component, and three or more detection elements. An
arithmetic processing unit that performs arithmetic processing on a plurality of sound wave
signals to detect sound waves, and the arithmetic processing unit performs subtraction
processing on each of two sound wave signals corresponding to adjacent detection elements; A
subtractor delaying device for adding a delay corresponding to the position of the detection
element corresponding to the sound wave signal to each sound wave signal subjected to
subtraction processing in a plurality of subtractors, and adding to the output from the subtractor
delaying device And a reduction value adder for performing processing.
[0020]
Further, in the sound wave detection method according to the present invention, a sound wave
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5
signal detection step of detecting a sound wave signal containing a sound wave component by
three or more detection elements arranged at intervals along the detection direction; Each of the
sound wave signals subjected to the subtraction process for performing subtraction processing
on each of the two sound wave signals corresponding to the elements and each sound wave
signal subjected to the subtraction process in the subtraction step is delayed according to the
position of the detection element for the sound wave signals. And a subtraction value adding step
of adding each signal delayed and outputted in the subtraction side delay step.
[0021]
According to the present invention, noises output from the same detection element are obtained
by performing delay processing according to the position of the detection element and
performing subtraction processing on two sound wave signals corresponding to adjacent
detection elements. Therefore, regardless of the frequency of the sound wave to be detected,
noise can be reduced, and the reduction in sensitivity and the occurrence of disturbance in
directivity can be suppressed.
[0022]
It is a schematic diagram which illustrates the composition of the acoustic sensor concerning a
1st embodiment of the present invention.
It is a flowchart which shows operation | movement of the acoustic sensor of FIG.
It is a schematic diagram which illustrates the composition of the acoustic sensor concerning a
2nd embodiment of the present invention.
It is a flowchart which shows operation | movement of the acoustic sensor of FIG. It is a
schematic diagram which illustrates the composition of the acoustic sensor concerning a 3rd
embodiment of the present invention. It is a schematic diagram which illustrates the structure of
the acoustic sensor which concerns on 4th Embodiment of this invention. It is a schematic
diagram which shows the structure of the acoustic sensor which concerns on a prior art. It is a
graph which shows the calculation result of the normalization sensitivity with respect to the
product of a wave number and the space | interval of two detection elements. It is a graph which
shows the gain of the integral process with respect to the product of a wave number and the
space | interval of two detection elements.
05-05-2019
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[0023]
First Embodiment FIG. 1 is a schematic view illustrating the configuration of an acoustic sensor
according to a first embodiment of the present invention. Unlike the acoustic sensor of the prior
art, the acoustic sensor of the first embodiment has three or more detection elements. Further, in
the acoustic sensor according to the first embodiment, the plurality of subtractors subtract each
sound wave signal corresponding to the adjacent detection elements, and the outputs from the
plurality of subtractors correspond to the positions of the respective detection elements. It is
configured to add after adding a delay. The configuration of the acoustic sensor 10 having four
detection elements will be described with reference to FIG.
[0024]
The acoustic sensor 10 includes four detection elements E 0 to E 3, a light source / demodulator
20, and an arithmetic processing unit 30. Each of the detection elements E 0 to E 3 is formed in a
cylindrical shape, and exhibits directivity as shown in FIG. 8 when detecting a sound wave
propagating from an angle of θ with respect to the detection direction. The detection elements E
0 to E 3 are arranged to be aligned on the same straight line. Hereinafter, the direction in which
the detection elements E 0 to E 3 are arranged is referred to as a detection direction. That is, the
detection elements E 0 to E 3 are arranged at predetermined intervals d in the detection
direction. Hereinafter, when collectively referring to the detection elements E 0 to E 3 or when
referring to a configuration equivalent to these, it is also referred to as a detection element E.
[0025]
The detection element E splits the light input from the light source / demodulator 20 into two
paths with different lengths and reflects the light by a mirror (not shown), thereby making the
interference light including the component of the sound wave as a sound wave signal. It is
something to detect. Further, the detection element E is configured to output the detected sound
wave signal to the light source / demodulator 20.
[0026]
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The light source / demodulator 20 includes a light source (not shown) for emitting light to each
of the detection elements E 0 to E 3, and each light modulated by each sound wave signal
detected in each of the detection elements E 0 to E 3 And a demodulator (not shown) that
individually demodulates to generate respective sound wave signals p 0 to p 3 corresponding to
the respective detection elements E 0 to E 3. That is, the light source / demodulator 20
demodulates the light modulated by the sound wave signal detected by the detection element E 0
to generate a sound wave signal p 0, and the light modulated by the sound wave signal detected
by the detection element E 1 Demodulation is performed to generate a sound signal p 1. Further,
the light source / demodulator 20 demodulates the light modulated by the sound wave signal
detected by the detection element E 2 to generate a sound wave signal p 2, and the light
modulated by the sound wave signal detected by the detection element E 3 Demodulation is
performed to generate a sound signal p 3. The light source / demodulator 20 is configured to
output the generated sound wave signals p 0 to p 3 to the arithmetic processing unit 30.
[0027]
As described above, in the first embodiment, the signal detected by the detection element E and
the signal generated by the light source / demodulator 20 are substantially the same, and thus
both are referred to as sound signals. Then, the sound wave signal generated by the light source
/ demodulator 20 is distinguished by the sign “p”. The same applies to the second to fourth
embodiments described later. Hereinafter, when collectively referring to the respective sound
wave signals p 0 to p 3 or when referring to signals of the same quality, they are also referred to
as a sound wave signal p.
[0028]
The arithmetic processing unit 30 performs arithmetic processing on the sound wave signals p 0
to p 3 to detect sound waves. The arithmetic processing unit 30 includes a plurality of
subtractors 40A to 40C, a subtraction side delay device 51, a signal adder 61, a subtraction
adder 62, an output adder 63, and an integration / amplifier 70. ing.
[0029]
Each of the subtractors 40A to 40C performs a subtraction process on each of the two sound
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8
wave signals p corresponding to the adjacent detection elements E. That is, each of the
subtractors 40A to 40C performs a subtraction process on each sound signal p corresponding to
the associated two detection elements E. In the first embodiment, the subtractor 40A subtracts
the sound wave signal p 0 corresponding to the detection element E 0 from the sound wave
signal p 1 corresponding to the detection element E 1. The subtractor 40B subtracts the sound
wave signal p 1 corresponding to the detection element E 1 from the sound wave signal p 2
corresponding to the detection element E 2. The subtractor 40C subtracts the sound wave signal
p 2 corresponding to the detection element E 2 from the sound wave signal p 3 corresponding to
the detection element E 3. Hereinafter, each of the subtractors 40A to 40C is also referred to as a
subtractor 40 when generically or when referring to a configuration equivalent to these.
[0030]
The subtraction-side delay device 51 applies a delay according to the position of the detection
element E corresponding to the sound wave signal p to each of the sound wave signals p
subjected to the subtraction processing in the plurality of subtractors 40. Here, it is assumed that
the delay applied to the sound wave signal p by the subtraction side delay unit 51 includes zero.
[0031]
More specifically, the subtraction-side delay device 51 has a subtraction-side delay device 51B
provided after the subtractor 40B and a subtraction-side delay device 51C provided after the
subtracter 40C. Hereinafter, the term “subtraction side delay device 51B” and the term
“subtraction side delay device 51C” may be collectively referred to as “subtraction side delay
device 51m”.
[0032]
The subtraction side delay device 51B is for applying a delay according to the position of the
corresponding detection element E 1 and detection element E 2 to the sound wave signal p 1 and
the sound wave signal p 2 subjected to subtraction processing in the subtractor 40 B. . The
subtraction-side delay device 51C applies a delay according to the position of the corresponding
detection element E 2 and detection element E 3 to the sound wave signal p 2 and sound wave
signal p 3 subjected to subtraction processing in the subtractor 40 C. .
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[0033]
In the first embodiment, the delay time of the subtraction side delay device 51B is the time when
the sound wave propagates from the middle point between the detection element E1 and the
detection element E2 to the middle point between the detection element E0 and the detection
element E1. And d / c. Further, the delay time of the subtraction-side delay device 51C is 2d / c,
which is a time during which the sound wave propagates from the middle point between the
detection element E 2 and the detection element E 3 to the middle point between the detection
element E 0 and the detection element E 1. It has become.
[0034]
However, when the propagation time changes due to the influence of reflection, diffraction or the
like of the detection element E, each delay time is corrected according to the propagation time.
Here, when the sound wave signal is incident from the detection direction, the sound wave
detected by the detection element E 3 is a combination of the sound wave directly incident and
the sound wave reflected by the other detection element E and returned to the detection element
E 3 It is a thing. Since the reflected sound waves are delayed from the sound waves directly
incident, the sound waves detected after reflection by the other detection elements E in one
detection element E have a delay from the timing of the sound waves incident directly. The sound
wave incident on the detection element E 2 has a component that is delayed due to the
diffraction around the detection element E 3, and such diffraction also causes the delay of the
sound wave detected by the detection element E. In particular, in a wave receiving element
having a structure in which an elastic body is inserted in an optical fiber coil as in the detection
element of Patent Document 2, since the reflection by the elastic body is large, the influence of
the delay of the sound wave becomes large. As an example of a method of correcting these
reflections, diffractions, etc., there is a method of making a sound wave incident on the acoustic
sensor 10, measuring the delay time of the sound wave signal detected in the detection element
E, and correcting using the delay time. Since the delay time changes depending on the direction
in which the sound wave is incident, if priority is given to increasing the sensitivity in the
detection direction, the sound wave is made incident from the detection direction and corrected
with the delay time measured. When priority is given to the suppression effect, sound waves are
incident from the opposite direction and corrected by the delay time measured.
[0035]
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10
By the way, in the arithmetic processing unit 30, the subtraction side delay device 51m is not
provided after the subtracter 40A. That is, in the first embodiment, the delay time according to
the positions of the detection element E 1 and the detection element E 0 with respect to the
sound wave signal p 1 and the sound wave signal p 0 to be subjected to subtraction processing in
the subtractor 40A is 0 There is. In other words, the delay applied by the subtraction-side delay
device 51 to the sound wave signal p 1 and the sound wave signal p 0 subjected to the
subtraction processing in the subtractor 40A is zero.
[0036]
The signal adder 61 adds the sound wave signals p 0 to p 3 generated in the light source /
demodulator 20 and outputs the result to the output adder 63. The reduction value adder 62
performs addition processing on the signals output via the subtracters 40A to 40C, that is, the
output from the subtraction-side delay device 51. More specifically, the reduction value adder 62
adds the signal output from the subtractor 40A, the signal output from the subtraction delay
device 51B, and the signal output from the subtraction delay device 51C, This signal is output to
the integration / amplifier 70.
[0037]
The integration / amplifier 70 amplifies the signal output from the reduction adder 62 by
integration processing and outputs the amplified signal to the output adder 63. The output adder
63 adds the signal output from the signal adder 61 and the signal output from the integration /
amplifier 70 to generate an acoustic wave based on the acoustic signal detected by each of the
detection elements E 0 to E 3. An output V is generated as information and output to the outside.
[0038]
Although the case where acoustic sensor 10 has four detection elements E0-E3 was shown as an
example in explanation of the above-mentioned composition, not only this but acoustic sensor
10, 3 or 5 or more arbitrary numbers The detection element E may be provided. For example,
when the acoustic sensor 10 includes N (N is an integer of 3 or more) detection elements E, the
arithmetic processing unit 30 includes N-1 subtractors 40 and N-2 subtractor delays 51m. And is
configured to have
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[0039]
That is, according to the acoustic sensor 10 of the first embodiment, from the sound wave signals
p i (i = 0, 1,..., N−1) corresponding to the N detection elements E 0 to E N−1, The operation
represented by the equation (6) is performed to obtain an output V which is information of a
sound wave.
[0040]
[0041]
When a sine wave of amplitude P and angular frequency ω propagating from the angle of θ
with respect to the detection direction is detected, p i and V are expressed by the following
equations (7) and (8), respectively.
As for the normalized sensitivity D, it can be seen from the above equation (5) that in the range
of kd <1, the sensitivity is high when θ = 0 and the sensitivity is low when θ = π (rad).
[0042]
[0043]
[0044]
In “Σ” in the two items of the equation (6), the sound wave signal p i corresponding to the
same detection element E for the sound wave signal p i corresponding to each of the detection
element E 1 to the detection element E N−1 is d / It is supposed to subtract it with a delay of c.
Here, since the noise output from the same detection element E has a large correlation even
when delayed, according to the acoustic sensor 10, the noise is reduced by arithmetic processing
in the subtractor 40 and the subtraction side delay device 51m. Can.
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That is, the acoustic sensor 10 performs the processing represented by the two items of the
equation (6) to generate noise from other than the detection element E (the detection element E 0
and the detection element E N-1) disposed at both ends. It can be attenuated.
[0045]
As described above, in the case of the conventional acoustic sensor, when the distance d is
increased, the sensitivity to the high frequency sound wave is lowered, and the directivity is
disturbed.
In this respect, the acoustic sensor 10 can lower the gain of the integration / amplifier 70 to a
level close to the case where the distance between the two detection elements in the conventional
acoustic sensor is increased from d to (N-1) d. For this reason, according to the acoustic sensor
10, it is possible to reduce the noise as well as to suppress the deterioration of the sensitivity to
the high frequency sound wave and the disturbance of the directivity.
[0046]
By the way, although the case where a sound wave signal is detected and generated using a
plurality of detection elements E and the light source / demodulator 20 has been described as an
example in the first embodiment, the present invention is not limited to this. For example, the
acoustic sensor 10 may have a plurality of detection elements using a piezoelectric material or
the like instead of the plurality of detection elements E and the light source / demodulator 20. As
a detection element using a piezoelectric material or the like, for example, a detection element
shown in Patent Document 1 (in Patent Document 1, it is described as a receiver or an
underwater receiver) can be adopted. Since a detection element using a piezoelectric material or
the like can directly detect an acoustic wave signal including a component of an acoustic wave
propagating in water, the acoustic wave signal is sent to the arithmetic processing unit 30
without passing through the light source / demodulator 20. It can be output.
[0047]
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FIG. 2 is a flowchart showing the operation of the acoustic sensor 10. A sound wave detection
method by the acoustic sensor 10 will be described with reference to FIG.
[0048]
First, the light source / demodulator 20 transmits light to each of the detection elements E 0 to E
3 (FIG. 2: step S101). And each detection element E0-E3 detects the sound wave signal
containing the component of the sound wave which propagates in water. That is, each of the
detection elements E 0 to E 3 modulates the light emitted from the light source / demodulator 20
with the sound wave signal (FIG. 2: step S102). Next, the light source / demodulator 20
individually demodulates the light modulated by each sound wave signal detected in each
detection element E 0 to E 3, and the sound wave corresponding to each of each detection
element E 0 to E 3 The signals p 0 to p 3 are generated (FIG. 2: step S103).
[0049]
Here, the three steps from step S101 to step S103 are steps in which each of the detection
elements E 0 to E 3 detects a sound wave signal including the component of the sound wave
propagating in the water. It corresponds to "signal detection step". When a plurality of detection
elements using a piezoelectric material or the like is used instead of the plurality of detection
elements E and the light source / demodulator 20, each of the detection elements is an acoustic
wave containing a component of the acoustic wave propagating in water. Signals can be directly
detected, generated and output. Therefore, in the case of the acoustic sensor 10 employing such
a detection element, the “sound wave signal detection step” of the present invention can be
realized by one process.
[0050]
Next, the arithmetic processing unit 30 performs subtraction processing on each of the two
sound wave signals p corresponding to the adjacent detection elements E by the subtractors 40A
to 40C (FIG. 2: step S104 / subtraction step). Further, the arithmetic processing unit 30 controls
the position of the detection element E corresponding to the sound wave signal p for each of the
sound wave signals p subjected to the subtraction process by the subtractors 40A to 40C by the
subtraction side delay device 51. Add a delay. That is, the subtraction side delay device 51B
delays the sound wave signal p 1 and the sound wave signal p 2, and the subtraction side delay
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device 51 C delays the sound wave signal p 2 and the sound wave signal p 3 (FIG. 2: step S105 /
Subtractive delay step).
[0051]
Subsequently, the signal adder 61 adds the sound wave signal p 0, the sound wave signal p 1, the
sound wave signal p 2, and the sound wave signal p 3 (FIG. 2: step S106 / signal addition step).
Further, the arithmetic processing unit 30 adds the signals output via the subtractors 40A to 40C
by the reduction value adder 62, that is, the respective signals to be delayed and output by the
subtraction-side delay device 51 FIG. 2: Step S107 / Reduction Value Addition Step).
[0052]
Then, the arithmetic processing unit 30 amplifies the output from the reduction value adder 62
by the integration / amplifier 70 (FIG. 2: step S108 / amplification step). Next, the arithmetic
processing unit 30 adds the output from the signal adder 61 and the output from the integration
/ amplifier 70 by the output adder 63 to generate an output V which is information of a sound
wave, and outputs it to the outside (FIG. 2: step S109 / output addition step).
[0053]
As described above, the acoustic sensor 10 according to the first embodiment applies a
subtraction process to the two sound wave signals p corresponding to the adjacent detection
elements E while applying a delay according to the position of the detection elements E. Because
of the above addition, the noise output from the same detection element E can be attenuated. The
acoustic sensor 10 can lower the gain of the integration / amplifier 70 as in the case where the
distance d between the two detection elements in the conventional acoustic sensor is increased to
N-1 times. Therefore, according to the acoustic sensor 10, regardless of the frequency of the
sound wave to be detected, noise can be reduced, and the reduction in sensitivity and the
occurrence of disturbance in directivity can be suppressed. Further, since the sensitivity of the
acoustic sensor 10 in the detection direction (θ = 0 °) is high in the range of kd <1 (see FIG. 8),
according to the acoustic sensor 10, the acoustic wave band that can be detected is a
conventional acoustic sensor Can be expanded to nearly N-1 times of.
05-05-2019
15
[0054]
Second Embodiment FIG. 3 is a schematic view illustrating the configuration of an acoustic
sensor according to a second embodiment of the present invention. In the acoustic sensor
according to the second embodiment, the sound wave signal p corresponding to the adjacent
detection element E is subjected to subtraction processing and addition processing by a plurality
of subtractors and a plurality of adders, and the output from each subtractor and each addition
The configuration is such that the output from the device is delayed according to the position of
each detection element E and then added. The configuration of the acoustic sensor 10A having
four detection elements E 0 to E 3 will be described with reference to FIG. The same members of
the present embodiment as those of the acoustic sensor 10 according to the first embodiment
described above are designated by the same reference numerals and the description thereof will
be omitted.
[0055]
As shown in FIG. 3, the acoustic sensor 10A includes a plurality of detection elements E 0 to E 3,
a light source / demodulator 20, and an arithmetic processing unit 30A. The arithmetic
processing unit 30A performs arithmetic processing on the respective sound wave signals p 0 to
p 3 and detects sound waves included in the sound wave signals detected by the respective
detection elements E 0 to E 3.
[0056]
The arithmetic processing unit 30A includes a plurality of subtractors 40A to 40C, a subtraction
side delay device 51B, a subtraction side delay device 51C, a reduction value adder 62, an output
adder 63, and an integration / amplifier 70. In addition, unlike the arithmetic processing unit 30
of the first embodiment described above, the arithmetic processing unit 30A adds a plurality of
binary adders 61A to 61C, an addition delayer 52B, an addition delayer 52C, and an addition
value. And an adder 64.
[0057]
Each of the binary adders 61A to 61C performs addition processing on each of the two sound
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wave signals p corresponding to the adjacent detection elements E. That is, each of the binary
adders 61A to 61C performs addition processing on each sound wave signal p corresponding to
the two associated detection elements E. In the second embodiment, the binary adder 61A adds
the sound wave signal p 0 corresponding to the detection element E 0 and the sound wave signal
p 1 corresponding to the detection element E 1. The binary adder 61 B adds the sound wave
signal p 1 corresponding to the detection element E 1 and the sound wave signal p 2
corresponding to the detection element E 2. The binary adder 61C adds the sound wave signal p
2 corresponding to the detection element E 2 and the sound wave signal p 3 corresponding to
the detection element E 3. In the following, when the binary adders 61A to 61C are collectively
referred to or referred to as the same configuration as these, they are also referred to as a binary
adder 61m.
[0058]
The addition-side delay device 52 applies a delay according to the position of the detection
element E corresponding to the sound wave signal p to each of the sound wave signals p
subjected to subtraction processing in the plurality of binary adders 61 m. . Here, it is assumed
that the delay applied to the sound wave signal p by the addition-side delay device 52 includes
zero.
[0059]
More specifically, the addition-side delay unit 52 includes an addition-side delay 52B provided
after the binary adder 61B and an addition-side delay 52C provided after the binary adder 61C.
There is. Hereinafter, the term “addition side delay 52 </ b> B” and the term “addition side
delay 52 </ b> C” are collectively referred to as “adding side delay 52 m”.
[0060]
The addition-side delay device 52B applies a delay according to the position of the corresponding
detection element E 1 and detection element E 2 to the sound wave signal p 1 and the sound
wave signal p 2 subjected to addition processing in the binary adder 61 B It is. The addition-side
delay device 52C applies a delay according to the position of the corresponding detection
element E 2 and detection element E 3 to the sound wave signal p 2 and sound wave signal p 3
subjected to addition processing in the binary adder 61 C. It is.
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[0061]
In the second embodiment, the adding delay unit 52B has the same configuration as the
subtracting delay unit 51B, and the adding delay unit 52C has the same configuration as the
subtracting delay unit 51C. Therefore, the delay time of the addition-side delay 52B is the time
for the sound wave to propagate from the middle point between the detection element E 2 and
the detection element E 3 to the middle point between the detection element E 1 and the
detection element E 2 d / c. It has become. Further, the delay time of the addition-side delay 52C
is 2d / c, which is the time for the sound wave to propagate from the middle point between the
detection element E 3 and the detection element E 4 to the middle point between the detection
element E 1 and the detection element E 2. It has become. However, when the propagation time
changes due to the influence of reflection, diffraction or the like of the detection element E, each
delay time is corrected according to the propagation time.
[0062]
By the way, in the arithmetic processing unit 30A, the addition side delay device 52m is not
provided after the binary adder 61A. That is, in the second embodiment, the delay time according
to the position of the detection element E 1 and the detection element E 0 with respect to the
sound wave signal p 1 and the sound wave signal p 0 subjected to subtraction processing in the
binary adder 61 A is 0 It has become. In other words, the delay applied to the sound wave signal
p 1 and the sound wave signal p 0 subjected to the subtraction process in the binary adder 61 A
is zero.
[0063]
The adder adder 64 performs addition processing on the signals output via the respective binary
adders 61A to 61C, that is, the output from the adder-side delay device 52. More specifically, the
adder adder 64 adds the signal output from the binary adder 61A, the signal output from the
addition delay unit 52B, and the signal output from the addition delay unit 52C. And output to
the integration / amplifier 70.
[0064]
05-05-2019
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Although the case where acoustic sensor 10A has four detection elements E0-E3 was shown as
an example in explanation of the above-mentioned composition, not only this but acoustic sensor
10A, three or five or more arbitrary numbers The detection element E may be provided. For
example, when the acoustic sensor 10A includes N (N is an integer of 3 or more) detection
elements E, the arithmetic processing unit 30A includes N−1 subtractors 40 and N−1 binary
adders 61m. , N-2 subtraction-side delay devices 51m, and N-2 addition-side delay devices 52m.
[0065]
That is, the acoustic sensor 10A of the second embodiment is based on the sound wave signal p i
(i = 0, 1,..., N−1) corresponding to the N detection elements E 0 to E N−1. Then, the calculation
represented by the following equation (9) is performed to obtain an output V which is
information of a sound wave.
[0066]
[0067]
When a sine wave of amplitude P and angular frequency ω propagating from the angle of θ
with respect to the detection direction is detected, p i is represented by the above equation (7),
and the output V is represented by the following equation (10) Ru.
As for the normalized sensitivity D, it can be seen from the above equation (5) that in the range
of kd <1, the sensitivity is high when θ = 0 and the sensitivity is low when θ = π (rad).
[0068]
[0069]
In the acoustic sensor 10A of the second embodiment, since the addition-side delay 52m is
provided after the binary adder 61m, it is possible to suppress the reduction in sensitivity to the
sound wave of higher frequency.
05-05-2019
19
A sound wave incident from a direction (reverse direction) opposite to the detection direction is
relatively quickly detected by the detection element E 0 and is detected late by the detection
element E N-1 (E 3 in FIG. 3).
Then, the signal detected by the detection element E N-1 is further delayed by the subtraction
side delay device 51C and the addition side delay device 52C. Here, the following equation (11) is
a modification of the above equation (9).
[0070]
[0071]
By the way, in the acoustic sensor 10 of the first embodiment, the reduction effect of the
sensitivity to the sound wave incident from the opposite direction becomes smaller than that of
the acoustic sensor constituted by only two detection elements E due to the influence of the delay
becoming large.
In this point, in the acoustic sensor 10A of the second embodiment, the inside of {} in the above
equation (11) has a form in which the delay in the above equation (1) is multiplied, and within {}
in which the same delay is applied. The term of is the same as the arithmetic processing in the
case of an acoustic sensor constituted of only two detection elements E. Therefore, even if the
terms in {} are added by Σ as in equation (11), the effect of reducing the sensitivity to the sound
wave incident from the opposite direction does not change. For this reason, according to the
acoustic sensor 10A, it is possible to obtain the same sensitivity reduction effect as in the case of
the acoustic sensor configured with only two detection elements E.
[0072]
FIG. 4 is a flowchart showing the operation of the acoustic sensor 10A. A sound wave detection
method by the acoustic sensor 10A will be described with reference to FIG.
05-05-2019
20
[0073]
First, the acoustic sensor 10A executes the operations of steps S101 to S103 as in the case of
FIG. Next, the arithmetic processing unit 30A performs addition processing on each of the two
sound wave signals p corresponding to the adjacent detection elements E by each of the binary
adders 61A to 61C (FIG. 4: step S201 / binary addition step) . Further, the arithmetic processing
unit 30A performs subtraction processing on each of the two sound wave signals p
corresponding to the adjacent detection elements E by the subtractors 40A to 40C (FIG. 4: step
S202 / subtraction step).
[0074]
Then, the arithmetic processing unit 30A responds to the position of the detection element E
corresponding to the sound wave signal p for each sound wave signal p subjected to the addition
processing by the binary adder 61 m by the addition-side delay device 52. A delay is applied (FIG.
4: step S203 / additional delay step). Further, the arithmetic processing unit 30A applies a delay
according to the position of the detection element E corresponding to the sound wave signal p to
each of the sound wave signals p to be subjected to the subtraction process by the subtractor 40
by the subtraction side delay device 51. (FIG. 4: Step S204 / subtraction side delay step).
[0075]
Subsequently, the arithmetic processing unit 30A causes the add value adder 64 to output the
signals output via the respective binary adders 61A to 61C, that is, the respective signals that are
delayed by the adding side delay device 52 and output. to add. More specifically, the adding
value adder 64 adds the signals output from the binary adder 61A, the adding delay 52B, and the
adding delay 52C (FIG. 4: step S205 / add value adding step). . Then, the arithmetic processing
unit 30A executes the operations of steps S107 to S109 as in the case of FIG.
[0076]
As described above, the acoustic sensor 10A of the second embodiment applies a subtraction
process to the two sound wave signals p corresponding to the adjacent detection elements E
while applying a delay according to the position of the detection elements E. Add up. Therefore,
05-05-2019
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the acoustic sensor 10A can attenuate the noise output from the same detection element E and
can lower the gain of the integration / amplifier 70. That is, according to the acoustic sensor
10A, regardless of the frequency of the sound wave to be detected, noise can be reduced, and the
reduction in sensitivity and the occurrence of disturbance in directivity can be suppressed.
[0077]
Furthermore, the acoustic sensor 10A can detect the acoustic wave with higher accuracy because
the sensitivity to the acoustic wave incident from the opposite direction is low as in the case of
the acoustic sensor configured with only two detection elements E. The other effects are similar
to those of the first embodiment described above.
[0078]
Third Embodiment FIG. 5 is a schematic view illustrating the configuration of an acoustic sensor
according to a third embodiment of the present invention. In the acoustic sensor according to the
third embodiment, the intervals between the detection elements E are made uneven, and the
delay time of each delay element is changed according to the arrangement interval of the
detection elements E. And the second embodiment. The configuration of the acoustic sensor 10B
in which the intervals between the detection elements E are nonuniform will be described with
reference to FIG. The same members of the present embodiment as those of the acoustic sensors
10 and 10A according to the first and second embodiments described above are denoted by the
same reference numerals and the description thereof will be omitted.
[0079]
As shown in FIG. 5, the acoustic sensor 10B has a plurality of detection elements E 0 to E 3, a
light source / demodulator 20, and an arithmetic processing unit 30B. In FIG. 5, the distance
between the detection element E 0 and the detection element E 1 is set to d 0, the distance
between the detection element E 1 and the detection element E 2 is set to d 1, and the detection
element E 2 and the detection element E It illustrates the case where the distance to 3 is set to d
2. There is a relationship of “d 0 <d 1 <d 2” between the interval d 0, the interval d 1 and the
interval d 2. That is, the detection elements E are arranged such that the distance between the
detection elements E increases in the detection direction.
05-05-2019
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[0080]
In the third embodiment, the demodulator included in the light source / demodulator 20
individually demodulates each light modulated by each sound wave signal detected in each
detection element E 0 to E 3, and each detection element E A plurality of sound wave signals p
B0 to p B3 corresponding to each of 0 to E 3 are generated. The arithmetic processing unit 30B
performs arithmetic processing on the sound wave signals p B0 to p B3 to detect sound waves.
Hereinafter, the sound wave signals p B0 to p B3 may be collectively referred to as “sound wave
signal p”.
[0081]
The arithmetic processing unit 30B includes a plurality of subtractors 40A to 40C, a subtraction
adder 62, an output adder 63, an addition adder 64, and an integration / amplifier 70. Further,
the arithmetic processing unit 30B includes a plurality of binary adders 61A to 61C and an
adjustment / delay device 53.
[0082]
The adjustment delay device 53 applies a delay to each of the sound wave signals p according to
the position of the detection element E corresponding to the sound wave signal p. Here, it is
assumed that the delay applied to the sound wave signal p by the adjustable delay device 53
includes zero. More specifically, the adjusting and delaying device 53 delays the sound wave
signals p subjected to the subtraction process and the addition process according to the position
of the detection element E corresponding to the sound wave signal p. Vessels 53A to 53D.
[0083]
The adder-subtractor 53A delays the sound wave signal p B1 corresponding to the detection
element E 1 and outputs it to the subtractor 40B and the binary adder 61B. The adder-subtractor
53B delays the sound wave signal p B2 corresponding to the detection element E 2 and outputs it
to the subtractor 40B and the binary adder 61B. The adder-subtractor 53C delays the sound
wave signal p B2 corresponding to the detection element E 2 and outputs it to the subtractor 40C
05-05-2019
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and the binary adder 61C. The adder-subtractor 53D delays the sound wave signal p B3
corresponding to the detection element E 3 and outputs it to the subtractor 40C and the binary
adder 61C. In the following, when collectively referring to each of the adjustment delay devices
53A to 53D or when referring to a configuration similar to these, it is also referred to as an
adjustment delay device 53m.
[0084]
In the third embodiment, the delay time of the add-subtractor 53A and the add-subtractor 53B is
a sound wave from the middle point between the detection element E 1 and the detection
element E 2 to the middle point between the detection element E 0 and the detection element E 1
Time for propagation ((d 0 + d 1) / (2c)). The delay time of the delaying device 53C and the
delaying device 53D is the time when the sound wave propagates from the middle point between
the detection element E 2 and the detection element E 3 to the middle point between the
detection element E 0 and the detection element E 1 ((d It is 0 + 2 d 1 + d 2) / (2 c)). However,
when the propagation time changes due to the influence of reflection, diffraction or the like of
the detection element E, each delay time is corrected according to the propagation time.
[0085]
Incidentally, in the arithmetic processing unit 30B, the adder / subtractor 53m is not provided in
front of the subtractor 40A and the binary adder 61A. That is, in the third embodiment, the delay
according to the position of the detection element E 1 and the detection element E 0 with respect
to the sound wave signal p B1 and the sound wave signal p B0 subjected to arithmetic processing
in the subtractor 40A and the binary adder 61A. The time is 0. In other words, the adder /
subtractor 53 applies a delay 0 to the sound wave signal p B1 and the sound wave signal p B0
and outputs the result to the subtractor 40A and the binary adder 61A.
[0086]
The binary adder 61A adds the sound wave signal p B0 and the sound wave signal p B1. The
subtractor 40A subtracts the sound wave signal p B0 from the sound wave signal p B1. The
binary adder 61B is disposed after the addition / subtraction device 53A and the addition /
subtraction device 53B. The binary adder 61B is to add the output of the addition / deletion
delay 53A and the output of the addition / deletion delay 53B. The subtractor 40B is disposed
05-05-2019
24
after the addition / subtraction device 53A and the addition / subtraction device 53B. The output
of the addition / subtraction device 53A is subtracted from the output of the addition /
subtraction device 53B. The binary adder 61C is disposed after the addition / subtraction device
53C and the addition / subtraction device 53D. The binary adder 61C is to add the output of the
addition / deletion delay 53C and the output of the addition / deletion delay 53D. The subtractor
40C is disposed after the addition / subtraction device 53C and the addition / subtraction device
53D. The output of the addition / subtraction delay 53C is subtracted from the output of the
addition / subtraction delay 53D. The reduction value adder 62 adds the signals output from the
subtractors 40A to 40C. The addition adder 64 adds the signals output from the binary adders
61A to 61C.
[0087]
Although the case where acoustic sensor 10B has four detection elements E0-E3 was shown as
an example in explanation of the above-mentioned composition, not only this but acoustic sensor
10B, three or five or more arbitrary numbers The detection element E may be provided. Here, the
distance between N (N is an integer of 3 or more) detection elements E is N-1 (d0, d1, ..., dN-2). In
the acoustic sensor 10B, the intervals between the detection elements E are irregular, and the
irregular intervals determine the position of the detection element E. In the acoustic sensor 10B,
the addition / subtraction device 53m delays each sound wave signal p i based on the position
according to the interval between the irregular detection elements E. However, at θ = 0 °, the
range in which the sensitivity is high is a range in which kd max <1 for the widest distance d max
of the detection elements E (d 2 in FIG. 3).
[0088]
That is, the acoustic sensor 10B of the third embodiment is based on the sound signal p i (i = 0,
1,..., N−1) corresponding to the N detection elements E 0 to E N−1. Then, the operation
represented by the following equation (12) is performed to obtain an output V which is
information of a sound wave. Here, τ i (i = 0, 1,..., N−1) is defined as the following equation
(13). Moreover, Formula (12) can be deform | transformed like following formula (14).
[0089]
[0090]
05-05-2019
25
[0091]
[0092]
The term in {} in equation (14) is a form multiplied by the delay in the above equation (1), and
the term in {} to which the same delay is applied is an acoustic signal composed of only two
detection elements E. It is the same as the arithmetic processing in the case of the sensor.
Therefore, even if the terms in {} are added by よ う as in equation (14), the sensitivity reduction
effect on the sound wave incident from the opposite direction can be obtained.
[0093]
The acoustic sensor 10B operates in the same manner as the acoustic sensor 10A of the third
embodiment described above, except that the delay corresponding to the non-uniform intervals
of the detection elements E is applied.
That is, in the sound wave detection method by the acoustic sensor 10B, a demodulation step of
individually demodulating each sound wave signal detected in each detection element E to
generate a sound wave signal p corresponding to each detection element E; Two acoustic waves
corresponding to the adjacent detection elements E and delayed in the addition and subtraction
delay steps, which add a delay corresponding to the position of the detection element E
corresponding to the sound wave signal p to each of p. It has a subtraction value subtraction step
of performing subtraction processing on each of the signals p, and a subtraction value addition
step of adding each signal output after the subtraction processing in the subtraction value
subtraction step.
Further, the sound wave detection method by the acoustic sensor 10B is a binary addition step of
performing addition processing on each of the two sound signals p corresponding to the adjacent
detection elements E and delayed in the addition / deletion delay step; And an addition value
addition step of adding each signal output after the addition processing in the binary addition
step.
05-05-2019
26
[0094]
Since the acoustic sensor 10B is configured and operates as described above, noise can be
reduced regardless of the frequency of the sound wave to be detected, and the reduction in
sensitivity and the occurrence of disturbance in directivity can be suppressed. By the way, like
the detection element of Patent Document 2, the detection element E is an optical fiber coil
formed by winding an optical fiber in a cylindrical shape, and a hollow elastic member disposed
inside the optical fiber coil with a space from the optical fiber coil. It can be configured to have a
body. Here, in the acoustic sensor 10 according to the first embodiment described above, when
the elastic modulus of the hollow elastic body included in the detection element E is reduced, the
phases of the reflected waves from the plurality of hollow elastic bodies at a frequency at which
the wavelength becomes equal to 2d. As a result, the disturbance of the sound field occurs
around each detection element E, which causes the directivity to be disturbed. In this respect,
since the acoustic sensor 10B according to the third embodiment makes the intervals between
the detection elements E uneven, the disturbance of the sound field can be suppressed. The same
effect as that of the second embodiment can be obtained.
[0095]
The sound waves incident on the detection element E include not only sound waves directly
incident but also sound waves reflected by other detection elements E. In the first embodiment,
for example, sound waves having a wavelength of 2 d are incident from the direction of θ = 180
° and are directly incident on the detection element E 0 and reflected by each of the detection
elements E 1, E 2, and E 3. The phases of the sound waves incident on the detection element E 0
are all equal. Therefore, the amplitude is increased by the sound waves detected by the other
detection elements E, and the suppression effect of the sound waves incident from the opposite
direction is reduced. On the other hand, in the third embodiment, the phase of the sound
reflected by each of the detection elements E 1, E 2, E 3 and incident on the detection element E
0 becomes nonuniform, so detection is performed by the detection element E Since the amplitude
error of the sound wave is reduced, the suppression effect of the sound wave incident from the
opposite direction is improved.
[0096]
05-05-2019
27
Although FIG. 5 exemplifies the case where there is a relationship of “d 0 <d 1 <d 2” between
the interval d 0, the interval d 1 and the interval d 2, the present invention is not limited to this.
For example, in the acoustic sensor 10B, “d 0 <d 1 = d 2”, “d 0 <d 1> d 2”, and “d 0 = d”
between the interval d 0, the interval d 1 and the interval d 2. 1 <d 2 "," d 0 = d 1> d 2 "," d 0> d 1
<d 2 "," d 0> d 1 = d 2 ", or" d 0> d 1> d 2 " It may be configured such that the following
relationship holds. The same applies to the case where the acoustic sensor 10B has three or five
or more arbitrary number of detection elements E. That is, the intervals between the detection
elements E may all be different intervals, or some of them may include the same interval.
[0097]
However, as shown in FIG. 5, when there is a relationship of “d 0 <d 1 <d 2” between the
interval d 0, the interval d 1 and the interval d 2, the reflection is performed by the detection
element E 3 having a long delay time. As a result, the propagation distance of the sound incident
on the detection element E 0 becomes long. Therefore, the sound wave is attenuated, the
amplitude error of the sound wave detected by the wave receiving element is reduced, and the
suppression effect of the sound wave incident from the opposite direction is improved. That is,
when the plurality of detection elements E are arranged such that the distance between the
adjacent detection elements E becomes larger in the detection direction, the suppression effect of
the sound wave incident from the opposite direction can be further improved. .
[0098]
However, the acoustic sensor 10B may unify the intervals of the plurality of detection elements E
and unify the intervals d as in the first and second embodiments. Then, for example, the addition
/ subtraction device 53 may add the same delay as the subtraction delay device 51 and the
addition delay device 52 of the first or second embodiment. Even in this case, the same effect as
the acoustic sensor 10A of the second embodiment can be obtained.
[0099]
Further, after unifying the intervals of the plurality of detection elements E by d, for example, the
acoustic sensor 10B is provided with the signal adder 61 instead of the addition adder 64
without providing the plurality of binary adders 61m. You may do so. In this case, the adjustable
delay device 53 may be configured to add the same delay as that of the subtractive delay device
05-05-2019
28
51 of the first embodiment. That is, the arithmetic processing unit 30B corresponds to each of
the detection elements E adjacent to each other, with the addition / subtraction device 53 that
applies a delay according to the position of the detection element E corresponding to the sound
wave signal p to each sound wave signal p. A plurality of subtractors 40 for performing
subtraction processing on each of the two sound signals delayed by the addition / subtraction
device 53, a subtraction adder 62 for performing addition processing on the outputs from the
plurality of subtractors 40, light source / demodulation And the signal adder 61 which adds each
sound wave signal p0-p3 produced | generated in the unit 20. FIG. Even in this case, the same
effect as the acoustic sensor 10 of the first embodiment can be obtained.
[0100]
Fourth Embodiment FIG. 6 is a schematic view illustrating the configuration of an acoustic sensor
according to a fourth embodiment of the invention. The acoustic sensor of the fourth
embodiment is different from the detection element E of each of the embodiments described
above in that the shapes of the detection elements are irregular. Here, the shape of the detection
element includes the shape of the detection element, the direction in which the detection element
is installed, and the presence or absence of division of the detection element, and when the
detection element is divided, the position of the divided detection element and The orientation
shall be included. The configuration of the acoustic sensor 10C in which the shapes of the
detection elements are irregular will be described with reference to FIG. The same members of
the present embodiment as those of the acoustic sensor 10A according to the second
embodiment described above are designated by the same reference numerals, and the
description thereof is omitted.
[0101]
As shown in FIG. 6, the acoustic sensor 10 </ b> C includes a plurality of detection elements E C0
to E C3, a light source / demodulator 20, and an arithmetic processing unit 30 </ b> A. In the
fourth embodiment, the detection element E C0 is configured in the same manner as the
detection element E in each of the embodiments described above. The detection element E C1 has
a shape divided into two, ie, is constituted by two detection elements. Each detection element is
formed in a cylindrical shape, and both are installed so as to face the detection direction. In each
detection element, the length along the detection direction is shorter than that of the detection
element E C0, and the cross-sectional area in the plane perpendicular to the detection direction is
larger than that of the detection element E C0. The detection element E C2 has a shape divided
into two, and each cylindrical detection element is installed so as to face in a direction
05-05-2019
29
perpendicular to the detection direction. Each detection element has the same size as each
detection element constituting the detection element E C1. The detection element E C3 is formed
in a cylindrical shape, and is installed so as to face in a direction perpendicular to the detection
direction. The length of the detection element E C3 in the vertical direction perpendicular to the
detection direction is longer than that of the detection element E C0, and the cross-sectional area
in the plane perpendicular to the vertical direction is smaller than that of the detection element E
C0. Hereinafter, when collectively referring to the respective detection elements E C0 to E C3 or
when referring to a configuration similar to these, it is also referred to as a detection element E C.
[0102]
In the fourth embodiment, the light source / demodulator 20 individually demodulates each light
modulated by each sound wave signal detected in each detection element E 0 to E 3 to form a
plurality of sound wave signals p C0 to p It generates C3. That is, the light source / demodulator
20 demodulates the light modulated by the sound wave signal detected by the detection element
E C0 to generate a sound wave signal p C0, and modulates the light modulated by the sound
wave signal detected by the detection element E C1 Demodulation is performed to generate a
sound signal p C1. The light source / demodulator 20 also demodulates the light modulated by
the sound wave signal detected from the detection element E C2 to generate a sound wave signal
p C2, and the light modulated by the sound wave signal detected by the detection element E C3
To generate a sound signal p C3. The light source / demodulator 20 is configured to output the
generated sound wave signals p C0 to p C3 to the arithmetic processing unit 30. Hereinafter, the
sound wave signals p C0 to p C3 may be collectively referred to as “sound wave signal p”.
[0103]
The operation of the acoustic sensor 10C, that is, the sound wave detection method by the
acoustic sensor 10C is the same as that of the acoustic sensor 10A of the second embodiment
described above. However, the influence on the propagation time due to the reflection, diffraction
or the like of the detection element E C is larger than that of the detection element E in the
second embodiment. For this reason, it is preferable to correct each delay time of the subtraction
side delay device 51m and the addition side delay device 52m according to the propagation time
changed due to the influence of reflection, diffraction or the like of the detection element E c.
[0104]
05-05-2019
30
Since the acoustic sensor 10C is configured and operates as described above, noise can be
reduced regardless of the frequency of a sound wave to be detected, and the reduction in
sensitivity and the occurrence of directivity disturbance can be suppressed. That is, according to
the acoustic sensor 10C, as in the acoustic sensor 10A of the second embodiment, an increase in
noise can be suppressed when the frequency of the sound wave to be detected is low, and as in
the acoustic sensor 10B of the third embodiment The disturbance of the field can be suppressed.
In addition, even if the distance between the detection elements E C is smaller than the structure
of the third embodiment in which the distance between the detection elements E is uneven, the
acoustic sensor 10C lowers the sensitivity in the case of detecting sound waves of high
frequency. And disturbance of directivity can be suppressed.
[0105]
By the way, although the case where all the shapes differ about each detection element Ec was
illustrated in the 4th embodiment of the present invention, not only this but a part of detection
elements Ec may be the same shape. That is, the plurality of detection elements E c of the
acoustic sensor 10C may be configured by combining detection elements E c of different shapes.
However, the shape of the detection element E C, that is, the shape of the detection element E C,
the direction in which the detection element E C is installed, and the like are not limited to the
example shown in FIG.
[0106]
The embodiments described above are preferable specific examples of the acoustic sensor and
the sound wave detection method, and the technical scope of the present invention is not limited
to these embodiments. For example, in the first embodiment, an example in which the
subtraction-side delay device 51m is disposed after the subtractor 40 and the integration /
amplifier 70 is disposed after the reduction value adder 62 has been described. The order of
arithmetic processing may be changed by changing the configuration of the acoustic sensor 10
as long as
[0107]
05-05-2019
31
Moreover, although the example which provides several subtractor 40 and the subtraction value
adder 62 was shown in 3rd Embodiment, it is not limited to this. The acoustic sensor 10B
corresponds to each detection element E on the detection direction side of each of the adjacent
detection elements E, for example, instead of each subtractor 40 and the reduction value adder
62, and the delay in the addition / subtraction device 53 is The first adder for adding each
applied sound wave signal p and each detection element E of the adjacent detection elements E
corresponding to each detection element E on the opposite side, and delayed by the addition /
subtraction device 53 A second adder for adding each sound wave signal p and a subtracter for
subtracting the output of the second adder from the output of the first adder may be provided.
Furthermore, the acoustic sensor 10B corresponds to the adjacent detection element E instead of
each arithmetic unit such as each subtractor 40 and the subtraction adder 62 or the first and
second adders and the subtractor, and an addition / subtraction device It is also possible to have
one adder / subtractor that executes addition processing for each of the two sound wave signals
p delayed at 53 and addition processing for each output of the addition processing. The
respective subtractors 40, the subtraction adders 62, and the first and second adders and the
subtracters are included in the "add / subtractor" in the present invention.
[0108]
In addition, in the third embodiment, an example in which the plurality of binary adders 61m and
the adders 64 are provided is shown, but the present invention is not limited to this. The acoustic
sensor 10B corresponds to, for example, each detection element E on the detection direction side
among the adjacent detection elements E instead of each binary adder 61m and the addition
adder 64, and The first adder for adding each delayed sound wave signal p and each detection
element E of the adjacent detection elements E correspond to each detection element E on the
opposite side, and the delay is added or decreased in the adder / subtractor 53 A second adder
for adding each applied sound wave signal p and a third adder for adding the output of the first
adder and the output of the second adder may be provided. The acoustic sensor 10B corresponds
to the adjacent detection element E instead of the plurality of adders such as each binary adder
61m and the adders 64 or the first to third adders, and the addition / subtraction device 53 It is
possible to have one addition operator that performs addition processing on each of the two
sound wave signals p delayed at time t and addition processing on each output of the addition
processing. The respective binary adders 61m, the adders 64, and the first to third adders are
included in the "addition operator" in the present invention.
[0109]
In the second and fourth embodiments, the subtractor-side delay unit 51m is disposed after the
subtractor 40, the addition-side delayer 52m is disposed after the binary adder 61m, and the
05-05-2019
32
reduction value adder 62 is disposed. Although the example which arrange | positions
integration and the amplifier 70 was shown, you may make it change the structure of acoustic
sensor 10A and 10C, and change the order of arithmetic processing in the range in which the
relationship equivalent to said Formula (9) is materialized.
[0110]
Furthermore, in the third embodiment, an example is described in which the addition /
subtraction device 53m is disposed before the subtractor 40 or the binary adder 61m, and the
integration / amplifier 70 is disposed after the subtraction adder 62. The configurations of the
acoustic sensors 10A and 10C may be changed as long as the same relationship as (9) holds, and
the order of the arithmetic processing may be changed.
[0111]
In the first embodiment, the output of the subtractor 40 is integrated. However, the acoustic
sensor 10 may be configured by a method of differentiating the output of the signal adder 61.
The same effect as described above can be obtained by the acoustic sensor 10 having such a
configuration.
Similarly, although the examples of integrating the output of the subtractor 40 are shown in the
second to fourth embodiments, a method of differentiating the output of the binary adder 61m
may be adopted. The same effects as described above can also be obtained by the acoustic
sensors 10A to 10C having such a configuration.
[0112]
In addition, although an example using an optical fiber acoustic sensor is shown in the second to
fourth embodiments, the acoustic sensors 10A to 10C may be, for example, detection elements
using a piezoelectric material as in the first embodiment. Other types of detection elements may
be used to directly detect the sound signal. The same effects as described above can also be
obtained by the acoustic sensors 10A to 10C having such a configuration.
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[0113]
Furthermore, in the first embodiment, the sound wave signal p corresponding to all the detection
elements E is added by the signal adder 61. However, the sound wave signal p corresponding to a
part of the detection elements E is added It may be configured. Alternatively, the sound wave
signal p corresponding to any one detection element E may be input to the reduction value adder
62 without using the signal adder 61.
[0114]
In addition, a configuration in which the intervals between the detection elements E are uneven
may be applied to the configurations of the first, second, and fourth embodiments, and each
detection element may be applied to the configurations of the first to third embodiments. A
configuration may be applied to make the shape of E irregular.
[0115]
10, 10A to 10C, 100 acoustic sensor, 20, 200 demodulator, 30, 30A, 30B arithmetic processing
unit, 40A, 40B, 40C, 400 subtractor, 51 subtractor delay device, 51B, 51C subtractor delay
device, 52 Adder delay device 52B, 52C Adder delay device, 53 add / drop delay device, 53A to
53D add / drop delay device, 61, 610 signal adder, 61A to 61C binary adder, 62 decrease value
adder, 63, 630 output Adder, 64 add value adder, 70, 700 integration / amplifier, E 0 to E 3, E
C0 to E C3 detection element, p 0 to p 3, p B0 to p B3, p C0 to p C3, p i Sound wave signal.
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34
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