JP6627563B2 - Acoustic sensor and sound wave detection method - Google Patents

Description

  The present invention relates to an acoustic sensor and a sound wave detection method.

  An example of an acoustic sensor that detects underwater sound waves is disclosed in Patent Document 1. The acoustic sensor disclosed in Patent Document 1 uses two detection elements that detect a sound wave signal including a sound wave component, has high sensitivity to sound waves propagating from the detection direction, and propagates from the opposite direction to the detection direction. It has directivity that lowers the sensitivity to incoming sound waves.

  An example of the detection element is disclosed in Patent Document 2. The detection element disclosed in Patent Document 2 has a structure in which an elastic body is placed in an optical fiber coil, and uses optical fiber distortion caused by sound waves to phase-modulate light. A signal detected by such a detection element can be demodulated using a demodulator shown in Non-Patent Document 1 or the like.

FIG. 7 is a schematic diagram illustrating a configuration of an acoustic sensor according to the related art. FIG. 7 shows an optical fiber acoustic sensor that detects underwater sound waves using an optical fiber as an acoustic sensor 100 that can be realized by the conventional techniques described in the above-mentioned documents. The acoustic sensor 100 has a detection element F and a detection element B that modulate light emitted from the light source / demodulator 200 with a sound wave signal. The detection element F and the detection element B are arranged at an interval d along the detection direction, and the detection element F is arranged closer to the detection direction than the detection element B. Source-demodulator 200 generates an acoustic signal p _F demodulates the modulated detection element F light, and generates an acoustic signal p _B demodulates the modulated detection element B light.

The acoustic sensor 100, based on the acoustic signal _{p F} and sonic signals _{p B} generated by the light source, the demodulator 200, the signal adder 610, subtractor 400, integrator-amplifier 700, and the output adder 630 The following equation (1) is used to obtain an output V that is information on sound waves.

Here, t is time and c is sound speed.
When detecting a sine wave having an amplitude P and an angular frequency ω propagating from an angle θ with respect to the detection direction, p _F , p _B , and V are expressed by the following equations (2) to (4), respectively. It is represented by

Here, k is a wave number.
The normalized sensitivity D in the equation (4) is represented by the following equation (5).

  FIG. 8 is a graph showing the calculation result of the normalized sensitivity D with respect to the product kd of the wave number k and the distance d between the two detection elements. FIG. 8 shows how the normalized sensitivity D changes in accordance with kd for θ = 0 and θ = π (rad). From FIG. 8, it can be seen that in the range of kd <1, the sensitivity is high when θ = 0, and the sensitivity is low when θ = π (rad).

JP 2007-12024 A JP 2012-68087 A

JASA Vol. 115, No. 6 “Acoustic Performance of a large-aperture, seabed, fiber-optic hydrophone array”

  However, in the conventional acoustic sensor 100, noise occurs due to a change in the wavelength of the light source. That is, in general, there are many uncorrelated components in the noise components of the sound wave signals corresponding to the two detection elements, so that the noise level does not decrease in the subtraction of the two items in the above equation (1). On the other hand, since the sound wave components of the sound wave signals corresponding to the two detection elements have a correlation, the signal level becomes lower in the subtraction of the two items in the above equation (1). Further, the lower the frequency of the sound wave to be detected, the greater the correlation between the sound wave components. Therefore, when detecting a sound wave with a low frequency, the signal level in the subtraction further decreases.

  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 the two detection elements. Since kd is proportional to the frequency, FIG. 9 shows that the gain increases as the frequency of the detected sound wave decreases. Therefore, in the processing by the conventional acoustic sensor 100, the lower the frequency of the sound wave to be detected, the greater the noise of the output, and the more difficult it is to detect a signal indicating a weak sound wave.

  In the conventional acoustic sensor 100, when the interval d is increased, the gain of the integration / amplifier 700 can be reduced, so that a part of noise can be suppressed. However, when the interval d is increased, the upper limit of the frequency range in which kd <1 is reduced, so that when a high-frequency sound wave is detected, a decrease in sensitivity and a disturbance in directivity occur. Furthermore, even in the case of an acoustic sensor having a detecting element using a piezoelectric material, the noise level generated by the amplifier lowers the signal level of the sound wave to be detected, similarly to the optical fiber acoustic sensor. Disturbance occurs. Therefore, there is a demand for an acoustic sensor and a sound wave detection method that reduce noise and suppress generation of sensitivity and disturbance of directivity regardless of the frequency of a sound wave to be detected.

  The acoustic sensors according to the present invention are arranged at intervals along the detection direction, and are detected by three or more detection elements, each of which detects a sound wave signal containing a sound 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, wherein the arithmetic processing unit performs a subtraction process on each of two sound wave signals corresponding to adjacent detection elements; A subtraction-side delay device that delays each of the sound wave signals subjected to the subtraction processing by the plurality of subtracters in accordance with the position of the detection element corresponding to the sound wave signal, and adds the delay time to the output from the subtraction-side delay device. And a subtraction adder for performing processing.

  In addition, the sound wave detection method according to the present invention includes a sound wave signal detecting step of detecting a sound wave signal containing a sound wave component by each of three or more detection elements arranged at intervals along the detection direction; A subtraction step of performing a subtraction process on each of the two sound wave signals corresponding to the element, and a delay corresponding to the position of the detection element corresponding to the sound wave signal on each of the sound wave signals subjected to the subtraction processing in the subtraction step And a subtraction step of adding each signal delayed and output in the subtraction side delay step.

  According to the present invention, since two sound wave signals corresponding to adjacent detection elements are delayed and added according to the position of the detection element and then added, the noise output from the same detection element is obtained. Can be attenuated, so that noise can be reduced irrespective of the frequency of the sound wave to be detected, and a decrease in sensitivity and the occurrence of disturbance in directivity can be suppressed.

FIG. 2 is a schematic view illustrating the configuration of the acoustic sensor according to the first embodiment of the present invention. 3 is a flowchart illustrating an operation of the acoustic sensor in FIG. 1. It is a mimetic diagram illustrating the composition of the acoustic sensor concerning a 2nd embodiment of the present invention. 4 is a flowchart illustrating an operation of the acoustic sensor in FIG. 3. It is a mimetic diagram illustrating the composition of the acoustic sensor concerning a 3rd embodiment of the present invention. It is a mimetic diagram illustrating the composition of the acoustic sensor concerning a 4th embodiment of the present invention. It is a schematic diagram which shows the structure of the acoustic sensor which concerns on a prior art. 9 is a graph showing a calculation result of normalized sensitivity with respect to a product of a wave number and an interval between two detection elements. 9 is a graph illustrating a gain of an integration process with respect to a product of a wave number and an interval between two detection elements.

[First Embodiment]
FIG. 1 is a schematic view illustrating the configuration of the acoustic sensor according to the first embodiment of the present invention. The acoustic sensor according to the first embodiment has three or more detection elements unlike the acoustic sensor according to the related art. Further, the acoustic sensor according to the first embodiment performs a subtraction process on each sound wave signal corresponding to an adjacent detection element by a plurality of subtracters, and outputs the outputs from the plurality of subtractors in accordance with the position of each detection element. The delay is added after the delay. The configuration of an acoustic sensor 10 having four detection elements will be described with reference to FIG.

The acoustic sensor 10 has 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 θ with respect to the detection direction. Each of the detection elements E _{0 to} E ₃ is arranged so as 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 a predetermined interval d along the detection direction. Hereinafter, when the detection elements E _{0 to} E ₃ are collectively referred to or when a configuration equivalent thereto is referred to, the detection elements E _{0 to} E ₃ are also referred to as detection elements E.

  The detection element E splits the light input from the light source / demodulator 20 into two paths having different lengths and reflects the light by a mirror (not shown), thereby converting the interference light including the sound wave component into a sound wave signal. It is to detect. The detection element E is configured to output the detected sound wave signal to the light source / demodulator 20.

Source-demodulator 20 includes a light source (not shown) for transmitting light to the detecting elements E ₀ to E _3, each light modulated by the acoustic signal detected at each detector element E ₀ to E ₃ demodulates individually contains respective sound signal p ₀ ~p ₃ demodulator that generates a corresponding to each of the detecting elements E ₀ to E ₃ (not shown). That is, the light source-demodulator 20 generates a sound signal p ₀ demodulates the light modulated by the acoustic signal detection element E ₀ is detected, the light detecting element E ₁ is modulated by the acoustic signal detected and it generates an acoustic signal p ₁ and demodulates. The light source-demodulator 20 generates a sound signal p ₂ demodulates the light modulated by the acoustic signal detection element E ₂ is detected, the light detection element E ₃ is modulated by the acoustic signal detected and it generates a sound signal p ₃ and demodulated. The light source-demodulator 20 is configured to output a respective ultrasonic signal p ₀ ~p ₃ generated to the arithmetic processing unit 30.

As described above, in the first embodiment, since the signal detected by the detection element E and the signal generated by the light source / demodulator 20 are substantially the same, both are referred to as sound wave signals. Then, the sound signal generated by the light source / demodulator 20 is distinguished by adding a symbol “p” to the sound signal. The same applies to the second to fourth embodiments described later. Later, when the called a signal or if these same quality collectively each acoustic signal p ₀ ~p _3, also referred to as a sound signal p.

The arithmetic processing unit 30 performs arithmetic processing on each of 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 value adder 62, an output adder 63, and an integration / amplifier 70. ing.

Each of the subtractors 40A to 40C performs a subtraction process on each of two sound wave signals p corresponding to the adjacent detection elements E. That is, each of the subtracters 40A to 40C performs a subtraction process on each sound wave signal p corresponding to the two detection elements E associated therewith. In the first embodiment, the subtractor 40A is to subtract the sound signal p ₀ corresponding to the detection element E ₀ from the sound wave signal p ₁ corresponding to the detection element E _1. Subtractor 40B is for subtracting a sound signal _{p 1} corresponding to the detection element _{E 1} from the sound wave signal _{p 2} corresponding to the detection element _{E 2.} Subtractor 40C is for subtracting a sound 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, when each of the subtractors 40A to 40C is collectively referred to or a configuration equivalent thereto is referred to, it is also referred to as a subtractor 40.

  The subtraction-side delay device 51 delays each of the sound wave signals p subjected to the subtraction processing in the plurality of subtracters 40 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 subtraction side delay device 51 includes 0.

  More specifically, the subtraction-side delay device 51 has a subtraction-side delay unit 51B provided after the subtractor 40B and a subtraction-side delay unit 51C provided after the subtractor 40C. Hereinafter, when the subtraction-side delay unit 51B and the subtraction-side delay unit 51C are collectively referred to or a configuration equivalent thereto is referred to, it is also referred to as a subtraction-side delay unit 51m.

Subtractor delay device 51B, the subtraction process is the acoustic signals p ₁ and acoustic signal p ₂ has been subjected in the subtractor 40B, in which applying a delay corresponding to the position of the corresponding detector elements E ₁ and detector element E ₂ . Subtractor delay device 51C is a subtracter wave subtraction process in 40C signal having undergone p ₂ and sonic signals p _3, it is intended to apply a delay corresponding to the position of the corresponding detector element E ₂ and detector element E ₃ .

In the first embodiment, the delay time of the subtractor of the delay device 51B, the time wave from the midpoint of the detector element E ₁ and the detection element E ₂ to the midpoint of the detector element E ₀ and the detection element E ₁ is propagated D / c. The delay time of the subtractor of the delay device 51C is sound waves from the midpoint between the detection element E ₂ and the detection element E ₃ to the midpoint of the detector element E ₁ and the detection element E ₀ is the time to propagate 2d / c It has become.

However, when the propagation time changes due to the influence of reflection, diffraction, and the like of the detection element E, each delay time is corrected according to the propagation time. Here, if the sound signal is incident from the detection direction, sound waves detected by the detector element E ₃ is a sound wave that has returned to the detection element E ₃ is reflected directly incident wave and the other detection element E is superimposed Things. Since the reflected sound wave is delayed from the directly incident sound wave, the sound wave detected by the certain detection element E after being reflected by the other detection element E is delayed from the timing of the directly incident sound wave. The sound waves incident on the detector element E _2, there is component incident late by diffraction at the periphery of the detector element E _3, these diffraction also cause a delay of the acoustic waves detected by the detector elements E. In particular, in a wave receiving element having a structure in which an elastic body is placed in an optical fiber coil, as in the detection element of Patent Document 2, the effect of the delay of the sound wave increases because the reflection by the elastic body is large. As an example of a method for correcting such reflection, diffraction, and the like, there is a method in which a sound wave is incident on the acoustic sensor 10, a delay time of a sound wave signal detected by the detection element E is measured, and correction is performed 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 incident from the detection direction and corrected by the measured delay time, and the sound wave incident from the opposite direction is corrected. When the suppression effect is prioritized, the correction is made based on the delay time measured by applying a sound wave from the opposite direction.

By the way, in the arithmetic processing unit 30, the subtractor 51m is not provided after the subtractor 40A. That is, in the first embodiment, the delay time corresponding to the position of the detector element E ₁ and detector element E ₀ regarding acoustic signals p ₁ and acoustic signal p ₀ subtraction process is performed in a subtractor 40A is a 0 I have. In other words, the subtraction side delay device 51, a delay to be applied to acoustic signals p ₁ and acoustic signal p ₀ subtraction process is performed in a subtractor 40A is zero.

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 subtraction value adder 62 performs an addition process on a signal output through each of the subtractors 40A to 40C, that is, an output from the subtraction side delay device 51. More specifically, the subtraction value adder 62 adds the signal output from the subtractor 40A, the signal output from the subtraction side delay unit 51B, and the signal output from the subtraction side delay unit 51C, It is output to the integrating / amplifier 70.

The integrator / amplifier 70 amplifies the signal output from the subtraction value adder 62 by an integration process and outputs the amplified signal to the output adder 63. Output summer 63, the signal output from the signal adder 61 adds the signal output from the integrator-amplifier 70, the sound waves based on the detected acoustic signals at each detector element E ₀ to E ₃ An output V is generated as information and output to the outside.

In the above description of the configuration, the case where the acoustic sensor 10 has four detection elements E _{0 to} E ₃ has been described as an example. However, the present invention is not limited thereto, and the acoustic sensor 10 may have any number of three or five or more. May be provided. For example, when the acoustic sensor 10 has 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 subtraction-side delay units 51m. And

That is, the acoustic sensor 10 according to the first embodiment obtains the following 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 calculation represented by the equation (6) is performed to obtain an output V that is information of a sound wave.

Amplitude P propagated through the angle θ with respect to the detection direction, when detecting a sine wave of angular frequency omega, p _i and V are respectively represented by the following formula (7) and (8). With respect to the normalized sensitivity D, from the above equation (5), it can be seen that in the range of kd <1, the sensitivity is high when θ = 0, and the sensitivity is low when θ = π (rad).

The "Σ" in the second term of formula (6), the sound signal p _i that corresponds to each of the detector elements E ₁ to the detecting element E _N-1, the sound signal p _i that correspond to the same detector element E d / The subtraction is performed with a delay of c. Here, since the noise output from the same detection element E has a large correlation even if it is delayed, according to the acoustic sensor 10, the noise is reduced by the arithmetic processing in the subtractor 40 and the subtraction side delay unit 51m. Can be. That is, the acoustic sensor 10 performs the process represented by the two items of the equation (6) to remove noise from the elements other than the detection elements E (detection elements E ₀ and E _N−1 ) disposed at both ends. Can be attenuated.

  As described above, in the conventional acoustic sensor, when the interval d is widened, the sensitivity to a high-frequency sound wave is reduced, and the directivity is disturbed. In this regard, the acoustic sensor 10 can reduce the gain of the integrating / 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. Therefore, according to the acoustic sensor 10, it is possible to suppress a decrease in sensitivity to a high-frequency sound wave and a disturbance in directivity, and to reduce noise.

  By the way, in the first embodiment, the case where the sound wave signal is detected and generated using the plurality of detection elements E and the light source / demodulator 20 has been described as an example, but 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 the detection element using a piezoelectric material or the like, for example, a detection element disclosed in Patent Document 1 (described as a receiver or an underwater receiver in Patent Document 1) can be employed. Since the detection element using a piezoelectric material or the like can directly detect a sound wave signal including a sound wave component propagating in water, the sound wave signal is transmitted to the arithmetic processing unit 30 without passing through the light source / demodulator 20. Can be output.

  FIG. 2 is a flowchart illustrating the operation of the acoustic sensor 10. With reference to FIG. 2, a sound wave detection method by the acoustic sensor 10 will be described.

First, the light source-demodulator 20, transmits light to the detecting elements _E 0 to E ₃ (Figure 2: step S101). Then, each of the detection elements E _{0 to} E ₃ detects a sound wave signal including a sound wave component propagating in water. That is, each of the detection elements E _{0 to} E ₃ modulates the light transmitted from the light source / demodulator 20 by the sound wave signal (FIG. 2: step S102). Next, the light source / demodulator 20 individually demodulates the light modulated by the sound wave signals detected by the respective detection elements E _{0 to} E ₃ , and outputs the sound waves corresponding to the respective detection elements E _{0 to} E _3. generating a signal _p 0 ~p ₃ (Figure 2: step S103).

Here, the three steps from step S101 to step S103, each detector element E ₀ to E _3, a step of detecting an acoustic signal containing a component of the sound waves propagated through the water, "waves of the present invention Signal detection step ". When a plurality of detection elements using a piezoelectric material or the like are used instead of the plurality of detection elements E and the light source / demodulator 20, each of the detection elements includes a sound wave including a sound wave component propagating in water. Signals can be directly detected, generated and output. Therefore, in the case of the acoustic sensor 10 employing such a detecting element, the “sound wave signal detecting step” of the present invention can be realized by one process.

Next, the arithmetic processing unit 30 performs a subtraction process on each of the two sound wave signals p corresponding to the adjacent detection elements E by each of the subtracters 40A to 40C (FIG. 2: Step S104 / subtraction step). Further, the arithmetic processing unit 30 assigns each of the sound wave signals p subjected to the subtraction processing by the subtractors 40A to 40C by the subtraction side delay device 51 to each of the sound wave signals p in accordance with the position of the detection element E corresponding to the sound wave signal p. Delay. That is, the subtractor of the delay circuit 51B is multiplied by a delay wave signals _{p 1} and acoustic signal _{p 2,} the subtractor of the delay device 51C is applied to the delay in acoustic signal _{p 2} and sound signals _{p 3} (Figure 2: step S105 / Subtraction side delay step).

Subsequently, the signal adder 61 adds the sound signals _{p 0} and acoustic signals _{p 1} and acoustic signal _{p 2} and sound signals _{p 3} (Figure 2: step S106 / signal adding step). Further, the arithmetic processing unit 30 adds the signals output via the subtractors 40A to 40C by the subtraction value adder 62, that is, the signals output after being delayed by the subtraction-side delay device 51 ( (FIG. 2: Step S107 / decrease value addition step).

  Then, the arithmetic processing unit 30 amplifies the output from the subtraction value adder 62 by the integration / amplifier 70 (FIG. 2: step S108 / amplification step). Next, the arithmetic processing unit 30 uses the output adder 63 to add the output from the signal adder 61 and the output from the integration / amplifier 70 to generate an output V that is information on sound waves, and output it to the outside. (FIG. 2: Step S109 / output addition step).

  As described above, the acoustic sensor 10 of the first embodiment applies the delay according to the position of the detection element E and the subtraction processing to the two sound wave signals p corresponding to the adjacent detection elements E. Since the above addition is performed, noise output from the same detection element E can be attenuated. The acoustic sensor 10 can lower the gain of the integrating / amplifier 70 as in the case where the distance d between two detection elements in a conventional acoustic sensor is increased to N-1 times. Therefore, according to the acoustic sensor 10, 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. Further, the sensitivity of the acoustic sensor 10 in the detection direction (θ = 0 °) is high in the range of kd <1 (see FIG. 8). Can be enlarged to nearly N-1 times of the above.

[Second embodiment]
FIG. 3 is a schematic view illustrating the configuration of the acoustic sensor according to the second embodiment of the present invention. The acoustic sensor according to the second embodiment performs a subtraction process and an addition process on a sound wave signal p corresponding to an adjacent detection element E by using a plurality of subtracters and a plurality of adders, and outputs the outputs from the respective subtracters and the respective additions. In this configuration, the output from the detector is added after a delay corresponding to the position of each detection element E. Referring to FIG. 3, the structure of the acoustic sensor 10A having four detector elements _E 0 to E _3. The same components as those of the acoustic sensor 10 according to the first embodiment described above are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 3, the acoustic sensor 10A includes a plurality of detector elements _E 0 to E _3, a light source-demodulator 20 has an arithmetic processing unit 30A, a. Arithmetic processing unit 30A is for performing an operation process on each acoustic signal p ₀ ~p _3, to detect the acoustic waves included in the detected sound signal in each detector element E ₀ to E _3.

  The arithmetic processing unit 30A includes a plurality of subtractors 40A to 40C, a subtraction side delay unit 51B, a subtraction side delay unit 51C, a subtraction value adder 62, an output adder 63, and an integration / amplifier 70. The arithmetic processing unit 30A is different from the arithmetic processing unit 30 of the first embodiment described above in that a plurality of binary adders 61A to 61C, an addition-side delay unit 52B, an addition-side delay unit 52C, And an adder 64.

Each of the binary adders 61A to 61C performs an addition process on each of two sound wave signals p corresponding to the adjacent detection elements E. That is, each of the binary adders 61A to 61C performs an addition process on each sound wave signal p corresponding to the two detection elements E associated therewith. In the second embodiment, the binary adder 61A is for adding the sound signal p ₁ corresponding to the detection element E ₁ and the ultrasonic signal p ₀ corresponding to the detection element E _0. Binary adder 61B is for adding the sound signal p ₂ corresponding to the sound signal p ₁ and the detection element E ₂ corresponding to the detection element E _1. Binary adder 61C is for adding the sound signal p ₃ corresponding to the sound signal p ₂ and the detection element E ₃ corresponding to the detection element E _2. Hereinafter, when each of the binary adders 61A to 61C is generically referred to or when the same configuration is referred to, it is also referred to as a binary adder 61m.

  The addition-side delay device 52 delays each of the sound signals p subjected to the subtraction processing in the plurality of binary adders 61m in accordance with the position of the detection element E corresponding to the sound signal p. . Here, it is assumed that the delay applied to the sound wave signal p by the adding-side delay device 52 includes 0.

  More specifically, the addition-side delay device 52 includes an addition-side delay device 52B provided after the binary adder 61B and an addition-side delay device 52C provided after the binary adder 61C. I have. Hereinafter, when the addition-side delay unit 52B and the addition-side delay unit 52C are collectively referred to, or when a configuration equivalent to these is referred to, it is also referred to as an addition-side delay unit 52m.

Adder of the delay circuit 52B is intended to apply addition processing on sound signals p ₁ and acoustic signal p ₂ are subjected in the binary adder 61B, a delay corresponding to the position of the corresponding detector elements E ₁ and detector element E ₂ It is. Adder of the delay circuit 52C is the sound signal p ₂ and sound signals p ₃ addition processing is performed in the binary adder 61C, which applies a delay corresponding to the position of the corresponding detector element E ₂ and detector element E ₃ It is.

In the second embodiment, the addition-side delay unit 52B has the same configuration as the subtraction-side delay unit 51B, and the addition-side delay unit 52C has the same configuration as the subtraction-side delay unit 51C. Therefore, the delay time of the adder of the delay circuit 52B is sound waves from the midpoint between the detection element E ₂ and the detection element E ₃ to the midpoint of the detector element E ₁ and the detection element E ₂ is the time to propagate d / c It has become. The delay time of the adder of the delay device 52C includes a 2d / c is the time wave from the midpoint of the detector element E ₃ and the detection element E4 to the midpoint of the detector element E ₁ and the detection element E ₂ is propagated Has become. However, when the propagation time changes due to the influence of reflection, diffraction, and the like of the detection element E, each delay time is corrected according to the propagation time.

Incidentally, in the arithmetic processing unit 30A, the addition-side delay unit 52m is not provided after the binary adder 61A. In other words, in the second embodiment, the delay time corresponding to the position of the detector element E ₁ and detector element E ₀ regarding acoustic signals p ₁ and acoustic signal p ₀ subtraction process is performed in the binary adder 61A is 0 and Has become. In other words, the adder of the delay device 52, a delay applied to the acoustic signals p ₁ and acoustic signal p ₀ subtraction process is performed in the binary adder 61A is 0.

  The adder 64 performs an addition process on a signal output via each of the binary adders 61A to 61C, that is, an output from the addition-side delay device 52. More specifically, the adder 64 adds the signal output from the binary adder 61A, the signal output from the addition-side delay unit 52B, and the signal output from the addition-side delay unit 52C. And outputs it to the integration / amplifier 70.

In the description of the above configuration, the case where the acoustic sensor 10A has four detector elements E ₀ to E ₃ as an example, not limited thereto, an acoustic sensor 10A includes three or any number of 5 or more May be provided. For example, when the acoustic sensor 10A has 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. And N-2 subtraction-side delay units 51m and N-2 addition-side delay units 52m.

That is, the acoustic sensor 10A of the second embodiment is based on the sound wave signals p _i (i = 0, 1,..., N−1) corresponding to the _N detection elements E _{0 to} E _N−1. Then, an operation represented by the following equation (9) is performed to obtain an output V that is information on sound waves.

Amplitude P propagated through the angle θ with respect to the detection direction, when detecting a sine wave of angular frequency omega, p _i is represented by the above formula (7), the output V is represented by the following formula (10) You. With respect to the normalized sensitivity D, from the above equation (5), it can be seen that in the range of kd <1, the sensitivity is high when θ = 0, and the sensitivity is low when θ = π (rad).

In the acoustic sensor 10A of the second embodiment, since the addition-side delay unit 52m is provided after the binary adder 61m, it is possible to suppress a decrease in sensitivity to a sound wave having a higher frequency. Waves and detecting a direction incident from the opposite direction (reverse direction), relatively, is detected early in the detector element E _0, it is detected late in the detection element E _{N-1 (in} FIG. 3 E _3). The signal detected by the detection element EN _-1 is further delayed by the subtractor 51C and the adder 52C.
Here, the following equation (11) is a modification of the above equation (9).

By the way, in the acoustic sensor 10 of the first embodiment, due to the effect of increasing the delay, the effect of reducing the sensitivity to the sound wave incident from the opposite direction is smaller than that of the acoustic sensor including only the two detection elements E.
In this regard, in the acoustic sensor 10 </ b> A of the second embodiment, the inside of {} in the above equation (11) is a form in which the delay is applied in the above equation (1), and the inside of the {} with the same delay is applied. Is the same as the arithmetic processing in the case of an acoustic sensor composed of only two detection elements E. Therefore, even if terms in {} are added by Σ as in equation (11), the effect of reducing the sensitivity to sound waves 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 including only the two detection elements E.

  FIG. 4 is a flowchart showing the operation of the acoustic sensor 10A. With reference to FIG. 4, a sound wave detection method by the acoustic sensor 10A will be described.

  First, the acoustic sensor 10A performs the operations of steps S101 to S103 in the same manner as in the case of FIG. Next, the arithmetic processing unit 30A performs an addition process 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 a subtraction process on each of the two sound wave signals p corresponding to the adjacent detection elements E by each of the subtracters 40A to 40C (FIG. 4: Step S202 / subtraction step).

  Then, the arithmetic processing unit 30A assigns each of the sound wave signals p subjected to the addition processing by the binary adder 61m to the position of the detection element E corresponding to the sound wave signal p by the addition side delay device 52. A delay is applied (FIG. 4: step S203 / addition-side delay step). Further, the arithmetic processing unit 30A delays each of the sound signals p subjected to the subtraction processing by the subtractor 40 by the subtraction side delay device 51 according to the position of the detection element E corresponding to the sound signal p. (FIG. 4: Step S204 / subtraction side delay step).

  Subsequently, the arithmetic processing unit 30A converts the signals output via the binary adders 61A to 61C, that is, the signals delayed and output by the addition-side delay device 52, by the adder 64. to add. More specifically, the value adder 64 adds the signals output from the binary adder 61A, the addition-side delay device 52B, and the addition-side delay device 52C (FIG. 4: Step S205 / value addition step). . Then, the arithmetic processing unit 30A executes the operations of steps S107 to S109 in the same manner as in the case of FIG.

  As described above, the acoustic sensor 10A according to the second embodiment applies the delay according to the position of the detection element E and the subtraction processing to the two sound wave signals p corresponding to the adjacent detection elements E. Add above. Therefore, the acoustic sensor 10A can attenuate the noise output from the same detection element E and lower the gain of the integrating / amplifier 70. That is, according to the acoustic sensor 10A, it is possible to reduce noise, regardless of the frequency of the sound wave to be detected, and to suppress a decrease in sensitivity and a disturbance in directivity.

  Furthermore, since the acoustic sensor 10A has a low sensitivity to a sound wave incident from the opposite direction, similarly to an acoustic sensor including only two detection elements E, the sound wave can be detected with higher accuracy. Other effects are the same as those of the first embodiment.

[Third embodiment]
FIG. 5 is a schematic view illustrating the configuration of the acoustic sensor according to the third embodiment of the present invention. The acoustic sensor according to the third embodiment employs a configuration in which the intervals between the detection elements E are made non-uniform and the delay time of each delay device 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 non-uniform will be described with reference to FIG. The same components as those of the acoustic sensors 10 and 10A of the above-described first and second embodiments are denoted by the same reference numerals, and description thereof is omitted.

As shown in FIG. 5, the acoustic sensor 10B includes a plurality of detector elements _E 0 to E _3, a light source-demodulator 20, has a calculation processing unit 30B, a. In Figure 5, the distance between the detector elements _{E 0} and the detection element _{E 1} is set to _{d 0,} the distance between the detector element _{E 1} and the detection element _{E 2} is set to _{d 1,} detector element _{E 2} and the detection element E spacing and ₃ illustrate a case where set to d _2. It is assumed that 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 respective detection elements E are arranged such that the distance between the respective detection elements E increases in the detection direction.

In the third embodiment, the demodulator included in the light source / demodulator 20 individually demodulates each light modulated by each sound signal detected by each of the detection elements E _{0 to} E ₃ , A plurality of sound 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 each of the sound wave signals p _{B0 to} p _B3 to detect sound waves. Hereinafter, when the sound wave signals p _{B0 to} p _B3 are collectively referred to or when signals of the same quality are referred to, they are also referred to as sound wave signals p.

  The arithmetic processing unit 30B includes a plurality of subtracters 40A to 40C, a subtraction value adder 62, an output adder 63, an addition value adder 64, and an integration / amplifier 70. In addition, the arithmetic processing unit 30B includes a plurality of binary adders 61A to 61C and an add / drop delay device 53.

  The adding / decreasing delay device 53 delays each sound wave signal p in accordance with 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 adjusting delay device 53 includes 0. More specifically, the add / drop delay device 53 includes a plurality of add / delay delays that apply a delay according to the position of the detection element E corresponding to the sound wave signal p to each sound wave signal p on which the subtraction process and the addition process are performed. Devices 53A to 53D.

Acceleration delay device 53A multiplies the delayed sound signal _{p B1} corresponding to the detector element _{E 1,} and outputs it to the subtractor 40B and binary adder 61B. Acceleration delay device 53B multiplies the delayed sound signal _{p B2} corresponding to the detection element _{E 2,} and outputs it to the subtractor 40B and binary adder 61B. Acceleration delay device 53C is multiplied by a delay in the sound signal _{p B2} corresponding to the detection element _{E 2,} and outputs to the subtracter 40C and the binary adder 61C. Acceleration delay device 53D multiplies the delayed sound signal _{p B3} corresponding to the detection element _{E 3,} and outputs to the subtracter 40C and the binary adder 61C. Hereinafter, when the respective adjustable delay devices 53A to 53D are collectively referred to or when the same configuration is referred to, these are also referred to as adjustable delay devices 53m.

In the third embodiment, the delay time of acceleration or delay device 53A and acceleration delay unit 53B is sound waves from the midpoint of the detector element E ₁ and the detection element E ₂ to the midpoint of the detector element E ₁ and the detection element E ₀ Is the propagation time ((d ₀ + d ₁ ) / (2c)). Acceleration delay device 53C and the delay time of the acceleration delay device 53D, the detection element E ₂ and the detection element E ₃ the midpoint of the detection element E ₀ and the detection element E ₁ and the time that sound waves to the midpoint propagate to the ((d ₀ + 2d ₁ + _d 2) and has a / (2c)). However, when the propagation time changes due to the influence of reflection, diffraction, and the like of the detection element E, each delay time is corrected according to the propagation time.

By the way, in the arithmetic processing unit 30B, the addition / subtraction delay unit 53m is not provided before the subtractor 40A and the binary adder 61A. In other words, in the third embodiment, according to the position of the subtracter 40A and sonic signals p _B1 and sonic signals p _B0 relating to the detection elements E ₁ and detector element E ₀ processing in the binary adder 61A is subjected delay The time is 0. In other words, the addition / subtraction delay device 53 delays the sound wave signal p _B1 and the sound wave signal p _B0 by zero, and outputs the result to the subtractor 40A and the binary adder 61A.

Binary adder 61A is for adding the sound signals _{p B0} and acoustic signal _{p B1.} The subtractor 40A subtracts the sound wave signal _pB0 from the sound wave signal _pB1 . The binary adder 61B is arranged after the adjustable delay device 53A and the adjustable delay device 53B. The binary adder 61B adds the output of the adjustable delay device 53A and the output of the adjustable delay device 53B. The subtractor 40B is arranged after the addition / subtraction delay unit 53A and the addition / subtraction delay unit 53B. This is to subtract the output of the adjustable delay device 53A from the output of the adjustable delay device 53B. The binary adder 61C is arranged after the adjustable delay device 53C and the adjustable delay device 53D. The binary adder 61C adds the output of the adjustable delay device 53C and the output of the adjustable delay device 53D. The subtractor 40C is arranged after the addition / subtraction delay unit 53C and the addition / subtraction delay unit 53D. This is to subtract the output of the adjustable delay device 53C from the output of the adjustable delay device 53D. The subtraction value adder 62 adds signals output from the respective subtracters 40A to 40C. The adder 64 adds signals output from the binary adders 61A to 61C.

In the description of the above configuration, the case where the acoustic sensor 10B has four detector elements E ₀ to E ₃ as an example, not limited thereto, an acoustic sensor 10B is three or any number of 5 or more May be provided. Here, the interval of the detector elements E of N (N is an integer of 3 or more) of _{N-1 (d 0, d} 1, ···, d N-2) only is present. In the acoustic sensor 10B, the intervals between the detection elements E are irregular, and the positions of the detection elements E are determined by the irregular intervals. In the acoustic sensor 10B, acceleration delay device 53m is, based on the position corresponding to the irregular spacing of each detector element E, applying a delay to the sound signal p _i. However, when θ = 0 °, the range in which the sensitivity is high is a range where kd _max <1 for the largest distance d _max (d _{2 in} FIG. 3) between the detection elements E.

That is, the acoustic sensor 10B of the third embodiment is based on sound wave signals p _i (i = 0, 1,..., N−1) corresponding to the _N detection elements E _{0 to} E _N−1. Then, an operation represented by the following equation (12) is performed to obtain an output V which is information on sound waves. Here, τ _i (i = 0, 1,..., N−1) is defined as in the following equation (13). Equation (12) can be modified as in the following equation (14).

  The expression in {} of Expression (14) is a form in which the delay is multiplied in Expression (1), and the term in {} to which the same delay is applied is a sound composed of only two detection elements E. This is the same as the calculation processing for the sensor. Therefore, even if the terms in {} are added by Σ as in equation (14), the effect of reducing the sensitivity to sound waves incident from the opposite direction can be obtained.

  The acoustic sensor 10B operates in the same manner as the acoustic sensor 10A of the above-described third embodiment, except that the acoustic sensor 10B applies a delay according to the non-uniform spacing of the detection elements E. That is, the sound wave detection method using the acoustic sensor 10B includes a demodulation step of individually demodulating each sound wave signal detected by each detection element E and generating a sound wave signal p corresponding to each detection element E; p to each of the two sound waves corresponding to the adjacent detection elements E and being delayed by the addition and subtraction delay steps. It has a subtraction step of performing subtraction processing on each signal p and outputting the same, and a subtraction addition step of adding each signal output after the subtraction processing in the subtraction step. Further, the sound wave detection method by the acoustic sensor 10B includes a binary addition step of performing an addition process on each of the two sound wave signals p corresponding to the adjacent detection elements E and delayed in the addition / subtraction delay step, and outputting the result. An addition step of adding signals output after the addition processing in the binary addition step.

Since the acoustic sensor 10B is configured and operates as described above, the acoustic sensor 10B can reduce noise, regardless of the frequency of the sound wave to be detected, and can suppress a decrease in sensitivity and a disturbance in directivity.
Incidentally, similarly to the detection element of Patent Document 2, the detection element E has an optical fiber coil configured by winding an optical fiber in a cylindrical shape, and a hollow elastic coil disposed inside the optical fiber coil with a space between the optical fiber coil and the optical fiber coil. And a body. Here, in the acoustic sensor 10 of the above-described first embodiment, when the elastic modulus of the hollow elastic body of the detection element E is reduced, the phase of the reflected waves from the plurality of hollow elastic bodies at a frequency at which the wavelength is equal to 2d. Are aligned, the sound field is disturbed around each detecting element E, which causes the directivity to be disturbed.
In this regard, in the acoustic sensor 10B of the third embodiment, since the intervals between the detection elements E are made non-uniform, the disturbance of the sound field can be suppressed, and thus the above-described range is satisfied in the range where kd _max <1. The same effect as in the second embodiment can be obtained.

The sound waves incident on the detection element E include not only sound waves directly incident on the detection element E but also sound waves reflected by other detection elements E. In the first embodiment, for example, a sound wave having a wavelength of 2d is incident from the direction of θ = 180 ° and is directly reflected on the detection element E ₀ and reflected by each of the detection elements E ₁ , E ₂ , and E _3. all sound waves in phase to to enter the detection element E ₀ is equal. Therefore, the amplitude increases due to the sound wave detected by the other detection element E, and the effect of suppressing the sound wave incident from the opposite direction decreases. On the other hand, in the third embodiment, since the phase of the sound reflected on each of the detection elements E ₁ , E ₂ , and E ₃ and incident on the detection element E ₀ becomes non-uniform, the sound is detected by the detection element E. Since the amplitude error of the sound wave is reduced, the effect of suppressing the sound wave incident from the opposite direction is improved.

Although FIG. 5 illustrates a case where “d ₀ <d ₁ <d ₂ ” is present between the interval d ₀ , the interval d _1, and the interval d ₂ , the relationship is not limited to this. For example, the acoustic sensor 10 </ b> B may include “d ₀ <d ₁ = d ₂ ”, “d ₀ <d ₁ > d ₂ ”, and “d ₀ = d” between the intervals d ₀ , d _1, and 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 ” May be configured so that the following relationship holds. This is the same also when 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 be all different intervals, or the same intervals may be partially included.

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 light is reflected by the detection element E ₃ having a long delay time. propagation distance of the sound incident on the detector element E ₀ and becomes longer. For this reason, the sound wave is attenuated, the amplitude error of the sound wave detected by the wave receiving element is reduced, and the effect of suppressing 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 increases in the detection direction, it is possible to further improve the effect of suppressing sound waves incident from the opposite direction. .

  However, in the acoustic sensor 10B, the intervals between the plurality of detection elements E may not be irregular, and may be unified with the interval d as in the first and second embodiments. Then, for example, the addition / subtraction delay device 53 may add the same delay as that of the subtraction-side delay device 51 and the addition-side 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.

In addition, after unifying the intervals between the plurality of detection elements E with d, for example, the acoustic sensor 10B is provided with the signal adder 61 instead of the additive adder 64 without providing the plurality of binary adders 61m. You may do so. In this case, the addition / subtraction delay device 53 may be configured to add the same delay as the subtraction-side delay device 51 of the first embodiment. That is, the arithmetic processing unit 30B corresponds to the adjusting / delaying device 53 that applies a delay according to the position of the detecting element E corresponding to the sound wave signal p to each sound wave signal p, and the adjacent detecting element E, and A plurality of subtractors 40 for performing a subtraction process on each of the two sound signals delayed by the addition / delay device 53; a subtraction adder 62 for performing an addition process on outputs from the plurality of subtracters 40; And a signal adder 61 that adds the sound wave signals p _{0 to} p ₃ generated in the device 20. Even in this case, the same effect as the acoustic sensor 10 of the first embodiment can be obtained.

[Fourth embodiment]
FIG. 6 is a schematic view illustrating the configuration of the acoustic sensor according to the fourth embodiment of the present invention. The acoustic sensor of the fourth embodiment is different from the detection elements E of the above embodiments 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 whether or not the detection element is divided.If the detection element is divided, the position and position of the divided detection element The orientation shall be included. With reference to FIG. 6, the configuration of the acoustic sensor 10C in which the shapes of the detection elements are irregular will be described. The same components as those of the acoustic sensor 10A according to the above-described second embodiment are denoted by the same reference numerals, and description thereof is omitted.

As illustrated in FIG. 6, the acoustic sensor 10C includes a plurality of detection elements E _{C0 to} E _C3 , a light source / demodulator 20, and an arithmetic processing unit 30A. In the fourth embodiment, the detection element _ECO is configured similarly to the detection element E in each of the above-described embodiments. The detection element E _C1 has a shape divided into two, that is, is configured by two detection elements. Each detection element is formed in a cylindrical shape, and is installed so that both are directed to the detection direction side. Each detection element has a length along the detection direction shorter than the detection element E _C0 , and a cross-sectional area on a plane perpendicular to the detection direction is larger than the detection element E _C0 . The detection element _EC2 has a shape divided into two, and each detection element formed in a cylindrical shape is installed so as to face in a direction perpendicular to the detection direction. Each detector element has a size comparable to the respective detecting elements constituting the detector element E _C1. The detection element _EC3 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 a plane perpendicular to the vertical direction is smaller than that of the detection element E _C0 . Hereinafter, when each of the detection elements E _{C0 to} E _C3 is collectively referred to or when a configuration similar to these is referred to, it is also referred to as a detection element E _C.

In the fourth embodiment, the light source / demodulator 20 individually demodulates each light modulated by each sound wave signal detected by each of the detection elements E _{0 to} E _{3 to} generate a plurality of sound wave signals p _{C0 to} p _{C0. C3} is generated. That is, the light source-demodulator 20 generates a sound signal p _C0 demodulates the light modulated by the acoustic signal detection element E _C0 detects the light detecting element E _C1 is modulated by the acoustic signal detected The sound wave signal p _C1 is generated by demodulation. The light source-demodulator 20 generates a sound signal p _C2 demodulates the light modulated by the acoustic signal detected from the detection element E _C2, detecting element E _C3 is modulated by acoustic signals detected light Is demodulated to generate a sound wave signal _pC3 . 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, when the sound wave signals p _{C0 to} p _C3 are collectively referred to or a signal of the same quality is also referred to as a sound wave signal p.

The operation of the acoustic sensor 10C, that is, the method of detecting sound waves by the acoustic sensor 10C is the same as that of the acoustic sensor 10A of the second embodiment described above. However, the reflection of the detection element E _C, the influence of the propagation time due to diffraction or the like is larger than the detector element E in the second embodiment. Therefore, reflection of the detection element E _C, depending on the propagation time varied effects such as diffraction, the subtractor of the delay unit 51m
It is preferable to correct each delay time of the addition-side delay unit 52m.

Since the acoustic sensor 10 </ b> C is configured and operates as described above, the acoustic sensor 10 </ b> C can reduce noise, regardless of the frequency of the sound wave to be detected, and can suppress the decrease in sensitivity and the occurrence of disturbance in directivity. That is, according to the acoustic sensor 10C, similarly to 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. The disturbance of the place 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 irregular, the acoustic sensor 10C has a reduced sensitivity when detecting a high-frequency sound wave. In addition, disturbance of directivity can be suppressed.

Incidentally, in the fourth embodiment, for each detector element E _C, although all shapes exemplified the case where different, not limited to this, part of the detection element E _C may be the same shape. That is, a plurality of detector elements E _C having acoustic sensor 10C may be configured by combining detector elements E _C of different shapes. However, the shape of the detector element E _C, i.e., the shape of the detector element E _C, orientation or the like for installing the detector element E _C is not limited to the example shown in FIG.

  The above-described embodiment is a preferred specific example 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 unit 51m is disposed after the subtractor 40 and the integration / amplifier 70 is disposed after the subtraction value adder 62 has been described. The configuration of the acoustic sensor 10 may be changed within the range where the condition is satisfied, and the order of the arithmetic processing may be changed.

  Further, in the third embodiment, the example in which the plurality of subtracters 40 and the subtraction value adders 62 are provided has been described, but the present invention is not limited to this. The acoustic sensor 10B corresponds to, for example, each detection element E in the detection direction of each of the adjacent detection elements E, instead of each of the subtracters 40 and the decrement value adders 62, and the delay in the addition / subtraction delay device 53 A first adder that adds the applied sound wave signals p, and a detection element E that is opposite to the detection direction of each of the adjacent detection elements E and that is delayed by the adjusting / delaying device 53. A second adder for adding the sound wave signals p and a subtractor for subtracting the output of the second adder from the output of the first adder may be provided. Further, the acoustic sensor 10B corresponds to an adjacent detection element E instead of a plurality of arithmetic units such as each of the subtractor 40 and the decremental adder 62 or the first and second adders and the subtractor, and further includes an add / drop delay device. It is also possible to have one adder / subtractor that performs addition processing on each of the two sound wave signals p delayed in 53 and addition processing on each output of the addition processing. Note that each of the subtractors 40 and the decremental adders 62 and the first and second adders and the subtractors are included in the “addition / subtraction unit” of the present invention.

  In addition, in the third embodiment, an example in which the plurality of binary adders 61m and the additive adders 64 are provided has been described, but the present invention is not limited to this. The acoustic sensor 10B corresponds to, for example, each detection element E in the detection direction of each of the adjacent detection elements E, instead of each of the binary adders 61m and the adder 64. A first adder for adding the delayed sound wave signals p, and each of the adjacent detection elements E corresponding to each of the detection elements E on the opposite side to the detection direction, and the delay in the adjusting / delaying device 53 A second adder for adding the applied sound wave signals p and a third adder for adding the output of the first adder and the output of the second adder may be provided. Then, instead of a plurality of adders such as the binary adder 61m and the adder 64 or the first to third adders, the acoustic sensor 10B corresponds to the adjacent detection element E, and has an add / drop delay device 53. May be added to each of the two sound wave signals p delayed, and one addition arithmetic unit that performs addition processing for each output of the addition processing. Note that each of the binary adders 61m and the adder 64, and the first to third adders are included in the "addition arithmetic unit" of the present invention.

  In the second and fourth embodiments, the subtraction side delay unit 51m is arranged after the subtractor 40, the addition side delay unit 52m is arranged after the binary adder 61m, and the subtraction side adder 62 is arranged after the subtraction unit 62. Although the example in which the integrator / amplifier 70 is arranged has been described, the configuration of the acoustic sensors 10A and 10C may be changed and the order of the arithmetic processing may be changed as long as the relationship equivalent to the above equation (9) is satisfied.

  Further, in the third embodiment, an example is shown in which the addition / subtraction delay unit 53m is arranged before the subtractor 40 or the binary adder 61m, and the integration / amplifier 70 is arranged after the subtraction adder 62. The configuration of the acoustic sensors 10A and 10C may be changed in a range where the same relationship as (9) is established, and the order of the arithmetic processing may be changed.

  In the first embodiment, the example in which the output of the subtracter 40 is integrated has been described. However, the acoustic sensor 10 may be configured by a method of differentiating the output of the signal adder 61. With the acoustic sensor 10 having such a configuration, the same effect as described above can be obtained. Similarly, in the second to fourth embodiments, the example in which the output of the subtracter 40 is integrated has been described, but a method of differentiating the output of the binary adder 61m may be adopted. With the acoustic sensors 10A to 10C having such a configuration, the same effect as described above can be obtained.

  In addition, in the second to fourth embodiments, an example in which the optical fiber acoustic sensor is used has been described. However, the acoustic sensors 10A to 10C have the same structure as the first embodiment, such as a detection element using a piezoelectric material. The sound wave signal may be directly detected using another type of detection element. With the acoustic sensors 10A to 10C having such a configuration, the same effect as described above can be obtained.

  Further, in the first embodiment, the example in which the sound wave signals p corresponding to all the detection elements E are added by the signal adder 61 has been described, but the sound wave signals p corresponding to some of the detection elements E are added. You may comprise. Further, the sound wave signal p corresponding to any one of the detection elements E may be input to the subtraction value adder 62 without using the signal adder 61.

  Further, a configuration in which the intervals between the detection elements E are irregular may be applied to the configurations of the first, second, and fourth embodiments, and each of the detection elements E may be added to the configuration of the first to third embodiments. A configuration in which the shape of E is irregular may be applied.

10, 10A to 10C, 100 Acoustic sensor, 20, 200 Demodulator, 30, 30A, 30B Operation processing unit, 40A, 40B, 40C, 400 Subtractor, 51 Subtraction-side delay device, 51B, 51C Subtraction-side delay device, 52 Addition-side delay device, 52B, 52C Addition-side delay device, 53 addition / subtraction delay device, 53A-53D addition / subtraction delay device, 61,610 signal adder, 61A-61C binary adder, 62 subtraction value adder, 63,630 output Adder, 64 adder, 70, 700 integrator / amplifier, E _{0 to} E ₃ , E _{C0 to} E _C3 detection elements, p _{0 to} p ₃ , p _{B0 to} p _B3 , p _{C0 to} p _C3 , p _i Sound wave signal.

Claims (11)

Three or more detection elements arranged at intervals along the detection direction, each detecting a sound wave signal including a sound wave component,
An arithmetic processing unit that performs arithmetic processing on the plurality of sound wave signals detected by the three or more detection elements to detect sound waves;
Has,
The arithmetic processing unit,
A plurality of subtracters for performing subtraction processing on each of the two sound wave signals corresponding to the adjacent detection elements;
A subtraction-side delay device that applies a delay corresponding to the position of the detection element corresponding to the sound wave signal to each of the sound wave signals subjected to the subtraction processing in the plurality of subtractors,
A subtraction adder for performing an addition process on an output from the subtraction-side delay device. The arithmetic processing unit,
A plurality of binary adders for performing an addition process on each of the two sound wave signals corresponding to the adjacent detection elements;
Each of the sound wave signals subjected to the addition processing in the plurality of binary adders, an addition-side delay device that delays according to the position of the detection element corresponding to the sound wave signal,
The acoustic sensor according to claim 1, further comprising: an adder that performs an addition process on an output from the adding-side delay device. Three or more detection elements arranged at intervals along the detection direction, each detecting a sound wave signal including a sound wave component,
An arithmetic processing unit that performs arithmetic processing on the plurality of sound wave signals detected by the three or more detection elements to detect sound waves;
Has,
The arithmetic processing unit,
Each of the plurality of sound wave signals, an adjustable delay device that applies a delay according to the position of the detection element corresponding to the sound wave signal,
A subtraction process for each of the two sound wave signals corresponding to the adjacent detection elements and delayed by the addition / delay device, and an addition / subtraction calculator that performs an addition process for each output of the subtraction process, Acoustic sensor having.   An addition operation unit that performs an addition process on each of the two sound wave signals corresponding to the adjacent detection elements and that has been delayed in the add / drop delay device, and an addition process on each output of the addition process, The acoustic sensor according to claim 3, comprising:   The acoustic sensor according to any one of claims 1 to 4, wherein three or more of the detection elements are arranged so that the intervals are irregular.   The acoustic sensor according to claim 5, wherein the three or more detection elements are arranged such that the interval increases in the detection direction.   The acoustic sensor according to any one of claims 1 to 6, wherein the three or more detection elements are configured by combining the detection elements having different shapes. A sound wave signal detecting step of detecting a sound wave signal including a sound wave component by each of three or more detection elements arranged at intervals along the detection direction;
A subtraction step of performing a subtraction process on each of the two sound wave signals corresponding to the adjacent detection elements;
Each of the sound wave signals subjected to the subtraction process in the subtraction step, a subtraction-side delay step of outputting a delay according to the position of the detection element corresponding to the sound wave signal,
A sound value detection method, comprising: a subtraction value addition step of adding signals output after being delayed in the subtraction side delay step. A binary addition step of performing an addition process on each of the two sound wave signals corresponding to the adjacent detection elements;
Each of the sound wave signals subjected to the addition process in the binary addition step, an addition-side delay step of outputting a delay according to the position of the detection element corresponding to the sound wave signal,
9. The sound wave detection method according to claim 8, further comprising: an addition step of adding each signal output after being delayed in the addition-side delay step. A sound wave signal detecting step of detecting a sound wave signal including a sound wave component by each of three or more detection elements arranged at intervals along the detection direction;
Each of a plurality of sound wave signals detected by three or more of the detection elements, an adjustable delay step of applying a delay according to the position of the detection element corresponding to the sound wave signal,
A decrement subtraction step of performing a subtraction process on each of the two sound wave signals corresponding to the adjacent detection elements and delayed in the addition and subtraction delay step, and outputting the subtracted signal;
A sound wave detection method, comprising: a subtraction value adding step of adding signals output after the subtraction processing in the subtraction value subtraction step. A binary addition step of performing an addition process on each of the two sound wave signals corresponding to the adjacent detection elements and being delayed in the addition / subtraction delay step, and outputting the result;
11. The sound wave detection method according to claim 10, further comprising: an addition step of adding signals output after the addition processing in the binary addition step.

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