JP3344335B2 - Acoustic sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic sensor for detecting the intensity of a sound signal in each frequency band in order to extract characteristics of the sound signal in voice recognition processing, sound signal processing, and the like.

[0002]

2. Description of the Related Art In a system for performing voice recognition, a microphone vibration receiving a voice signal is converted and amplified into an electric signal by an amplifier, and then an analog signal is converted into a digital signal by an A / D converter. A signal is obtained, and the audio digital signal is subjected to a fast Fourier transform by software on a computer to extract features of the audio. For such a speech recognition system, see IE
EE Signal Processing Magazine, Vol.13, No.5, pp.45
-57 (1996).

[0003] In order to efficiently extract the characteristics of an audio signal, it is necessary to calculate an acoustic spectrum within a time period in which the audio signal can be considered to be stationary. In the case of an audio signal, it is generally considered that the audio signal can be regarded as stationary within a time of 10 to 20 msec. Therefore, signal processing such as fast Fourier transform is executed by software on a computer with respect to the audio digital signal included within the time period of 10 to 20 msec.

As described above, in the conventional speech recognition system,
The audio signal including the entire instantaneous band is converted into an electric signal by a microphone, and in order to analyze the spectrum of the electric signal, A / D conversion is performed to digitize each frequency, and the audio digital signal data is specified. The characteristics of the sound are extracted by comparing with the data of the sound waveform.

[0005] Such a speech recognition system has a problem that the amount of calculation is enormous and the calculation load is large because the digital audio signal is subjected to a fast Fourier transform process and the spectrum of the audio signal is analyzed.

There is no problem with voices such as vowels in which the acoustic spectrum does not change with time, but a combination of consonants and vowels, for example,
A sound in which the consonant first appears and the vowel intensity increases with time, such as "ka, ki, k, ke, ko, sa, ta", or a complex consonant and vowel as in English The following problem arises with the sound in combination with the following. Conventionally, voices are recorded instantaneously, and the sound spectrum is analyzed by integrating the acoustic spectrum of the entire band at regular intervals, so it is difficult to determine at what point the consonant changed to a vowel As a result, the discrimination rate of voice recognition has been reduced. In order to solve this problem, more voice patterns are stored in the computer in advance and applied to any of these voice patterns, but this causes an increase in the computational load. ing.

The present inventors have proposed an acoustic sensor capable of solving these problems in M. Harada et al., "Resonator Array.
Sensor toward Artificial Cochlear Modeling, "Tech
nical Digest of the 15th Sensor Symposium, pp.97-1
00 (1997).

FIG. 7 is a plan view showing a configuration of a main part of the disclosed acoustic sensor and a sectional view taken along line VII-VII of FIG. This acoustic sensor has a rectangular table-shaped sensor body 2 formed on a semiconductor silicon substrate by a CMOS process, and a rectangular plate-shaped receiver formed as substantially half (left side in FIG. 7) of the upper plane portion of the sensor body 2. A corrugated portion 23, a rod-shaped holding portion 22 laid on the remaining portion of the upper flat portion in the left-right direction in FIG. 7, and a plurality of rod-shaped resonators 25 protrudingly provided on both sides of the holding portion 22, respectively. , 25,...

When the sound wave propagated in the air is transmitted to the wave receiving section 23, the wave receiving section 23 formed of a diaphragm vibrates, and the vibration propagates in the holding section 22. At this time, the sound waves sequentially increase in length from the left to the right in FIG.
It is transmitted while vibrating. Each resonator 25 has a unique resonance frequency, and resonates when a sound wave of the unique frequency propagates, and its tip vibrates up and down. Due to this vibration, the capacitance of the capacitor formed between the tip portion and the electrodes provided on the semiconductor silicon substrate below the tip portion changes. By obtaining the vibration intensity for each frequency of each resonator 25 based on this change, the detection of the acoustic signal and the frequency spectrum analysis can be performed at high speed and accurately on one piece of hardware, and the low frequency The frequency spectrum analysis can be performed with high accuracy on the side.

[0010]

In the acoustic sensor as described above, further improvement in detection sensitivity has been required in recent years. It is conceivable to increase the size of the wave receiving unit 23 in response to this, but there is a problem that the size of the entire acoustic sensor increases by the increase in the wave receiving unit 23.

The present invention has been made in view of such circumstances, and by arranging a plurality of wave receiving units and resonators which have been conventionally arranged side by side, it is possible to avoid an increase in the size of the entire acoustic sensor. It is another object of the present invention to provide an acoustic sensor capable of improving detection sensitivity.

[0012]

According to a first aspect of the present invention, there is provided an acoustic sensor having a plate-like wave receiving portion for receiving a sound wave propagating in a medium;
A plurality of resonators each resonating at a different frequency of the sound wave received by the wave receiving unit, and an acoustic sensor including a vibration intensity detection unit that detects a vibration intensity at which each resonator resonates, At least one and the wave receiving unit are provided in a stacked manner.

The acoustic sensor according to a second aspect of the present invention is the acoustic sensor according to the first aspect, further comprising a holding unit that connects the wave receiving unit and the plurality of resonators and holds the plurality of resonators. Are connected at a central portion of the wave receiving section.

An acoustic sensor according to a third aspect of the present invention is the acoustic sensor according to the first aspect, further comprising a supporting portion for movably supporting the wave receiving portion.

An acoustic sensor according to a fourth aspect of the present invention is the acoustic sensor according to the first or second aspect, further comprising a holding portion for holding the wave receiving portion.

The acoustic sensor according to a fifth aspect of the present invention is the acoustic sensor according to the third aspect, wherein the supporting portion supports the wave receiving portion via an elastic body.

In the acoustic sensor according to the first aspect of the invention, the sound wave propagated through the medium is received by the wave receiving unit, and the received sound wave is provided to a plurality of resonators that resonate at different frequencies.
Since the acoustic sensor configured to detect the vibration at each resonator with the vibration intensity detection unit is provided by stacking at least one of the plurality of resonators and the wave receiving unit, the size of the entire acoustic sensor is Without increasing the detection sensitivity.

[0018] In the acoustic sensor according to the second aspect of the present invention, the holding section for connecting and holding the plurality of resonators and the wave receiving section includes:
Because it was configured to be connected at the central part of the wave receiving unit,
For example, it is possible to transmit the vibration to the holding unit at the largest portion of the vibration of the wave receiving unit formed of a diaphragm,
The wave receiving unit can be used most efficiently. Therefore, larger vibration can be transmitted from the wave receiving unit to the holding unit than in the conventional configuration in which the holding unit is in contact with the side surface of the wave receiving unit, and the detection sensitivity can be further improved. . If the conventional detection sensitivity is maintained, the size of the wave receiving unit itself can be reduced.

In the acoustic sensor according to the third aspect of the present invention, since the wave receiving portion is configured to freely support the wave receiving portion, the holding portion is in contact with the other portion, not near the center of the wave receiving portion. Also in this case, the vibration of the wave receiving unit can be efficiently transmitted to the holding unit, and in such a case, the detection sensitivity can be improved.

[0020] In the acoustic sensor according to the fourth aspect of the invention, the wave receiving portion is held. Therefore, when the holding portion is in contact with the vicinity of the central portion of the wave receiving portion, the wave receiving portion is prevented from moving. The entire vibration can be efficiently transmitted to the holding unit,
Even in such a case, the detection sensitivity can be improved.

[0021] In the acoustic sensor according to the fifth aspect of the invention, since the wave receiving portion is supported via an elastic body, the holding portion is not in contact with the central portion of the wave receiving portion but in contact with other portions. In this case, it is possible to achieve a floating holding state as in the wave receiving section in the acoustic sensor of the third invention.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments.

(First Embodiment) FIG. 1 is a front view showing a configuration of a main part of a first embodiment of an acoustic sensor according to the present invention, and a sectional view taken along line II of FIG. The acoustic sensor according to the present embodiment includes a sensor main body 2a formed on a semiconductor silicon substrate (not shown), an electrode 3 described later, and a detection circuit 4 as a peripheral circuit.

The sensor body 2a has a rectangular plate shape,
The right half thereof is omitted except for the edge portion, and all of these portions are formed of semiconductor silicon. Further, a plurality of sensor bodies 2a having different lengths (12 in this example)
Resonating portion 21 having a rod-like portion, plate-like holding portion 22 for holding resonating portion 21 on the fixed end side of resonance, and short rod-shaped propagation standing upright at one end of holding portion 22. Part 26
And a plate-shaped wave receiving portion 23a connected to the propagation portion 26 and receiving the sound wave propagated in the air.

The wave receiving section 23a is composed of a diaphragm configured to dispose the propagation section 26 at the center thereof and to cover the entire portion of the resonance section 21.
It is fixed to the upper surface of.

The resonating portion 21 is a cantilever, and each bar-shaped portion is composed of six pairs of resonators 25 whose length is adjusted so as to resonate at a specific frequency.
Each resonator 25 has a resonance frequency f expressed by the following equation (1).
Oscillates selectively in response.

F = (CHE ^1/2 ) / (L ² ρ ^1/2 ) (1) where: C: constant determined experimentally H: thickness of each resonator 25 L: each resonator 25 Length E: Young's modulus of material (semiconductor silicon) ρ: Density of material (semiconductor silicon)

As can be seen from the above equation (1), by changing the thickness H or the length L of each resonator 25, its resonance frequency f can be set to a desired value.
5 has a unique resonance frequency (see FIG. 2). Note that the pair of resonators 25, 25 connected to the same position in the longitudinal direction of the holding unit 22 have the same resonance frequency. The thickness H of all the resonators 25 is fixed.

The length L is set to the left side (the propagation section 26 side).
Resonator 2 so that it becomes longer gradually from
5, 25, ... are arranged. Thus, the resonance frequency at which each resonator 25 inherently vibrates from the left side to the right side is set from a high frequency to a low frequency.

Specifically, the resonators 25, 25,...
It is possible to handle from high frequency to low frequency within a range of about kHz.

The holding section 22 has a width equal to that of the wave receiving section 2.
A configuration that improves the propagation sensitivity of the holding unit 22 is also possible as a configuration that is thickest in the vicinity of 3a and gradually narrows from there toward the right side in FIG.

The sensor main body 2a having the above configuration
Is formed on the semiconductor silicon substrate using a semiconductor integrated circuit manufacturing technique or a micromachining technique. In such a configuration, when a sound wave is transmitted to the wave receiving portion 23a, the plate-shaped wave receiving portion 23a vibrates, and the vibration indicating the sound wave propagates to the holding portion 22 via the propagation portion 26, and is held there. The rod-shaped resonators 25 of the resonating portion 21 are transmitted from the left to the right in FIG. 1 while sequentially resonating at respective specific frequencies.

The shape of the wave receiving portion 23a is preferably rectangular in order to obtain the maximum area of the diaphragm, since the sensor main body 2a has a rectangular planar shape. In order to reduce the signal noise and reduce the signal noise, it is preferable that the shape is a disk shape or an elliptical shape. Further, although processing is difficult, by forming a three-dimensional shape such as a cone, not only signal noise can be further suppressed, but also the receiving sensitivity can be improved. This is because it is easy to efficiently converge acoustic waves. In addition, by forming the shape into a polygon and / or a polyhedron, it is possible to obtain a suitable wave receiving portion 23a that meets appropriate design specifications.

In the design of the wave receiving section 23a as described above, it is possible to use a diaphragm design method used for transmitting and receiving waves such as an ultrasonic sensor and an ultrasonic microphone.

Further, in the present embodiment, silicon crystal is used as a material of the wave receiving portion 23a so as to be able to be processed integrally with the semiconductor silicon substrate. Materials such as ceramics can be used, and one of these materials is selectively used to improve the matching of acoustic impedance.

FIG. 2 is a perspective view for explaining the operation principle of the acoustic sensor according to the present invention. In FIG.
The wave receiving section 23a shows only the vicinity of the propagation section 26, respectively.

As shown in FIG. 2, an appropriate bias voltage V _bias is applied to the sensor body 2a, and the tip of each resonator 25 of the resonance section 21 and the semiconductor silicon at a position facing the tip are provided. A capacitor is constituted by the electrode 3 formed on the substrate. The tip of each resonator 25 is a movable electrode whose position moves up and down with these vibrations, while the electrode 3 formed on the semiconductor silicon substrate is a fixed electrode whose position does not move. When each resonator 25 vibrates at a specific frequency, the distance between the two electrodes changes, so that the capacitance of the capacitor changes.

Each electrode 3 is connected to a detection circuit 4 which converts such a change in capacitance into a voltage signal, integrates the converted voltage signal within a predetermined time, and outputs the integrated signal.

[0039] FIG. 3 is a block diagram showing the configuration of the detection circuit 4, the detection circuit 4 includes an operational amplifier for amplifying at amplification ratio corresponding to an impedance ratio between the capacitor C _s and the reference capacity C _f of the capacitor 41, 42, an integrating circuit 43 for integrating the output signal of the operational amplifier 42 higher than the reference voltage _Vref for a predetermined time, and a sample and hold circuit 44 for taking out the output signal from the integrating circuit 43, temporarily holding the output signal, and outputting it.
And The detection circuit 4 having such a configuration is formed by, for example, a silicon CMOS process.

The operational amplifier 41, the integrating circuit 43, and the sample-and-hold circuit 44 supply clock pulses φ ₀ ,
φ ₁ and φ ₂ are supplied, and the operational amplifier 41, the integrating circuit 43, and the sample and hold circuit 44 operate in synchronization with these clock pulses, respectively. These clock pulses may be supplied from outside,
A counter circuit may be formed on the same semiconductor silicon substrate and supplied from there.

When the sound wave propagated in the air is transmitted to the wave receiving portion 23a, the plate-shaped wave receiving portion 23a vibrates, and the vibration propagates through the propagation portion 26 in the sensor main body 2a. On this occasion,
Since the edge portion of the wave receiving portion 23a is fixed to the upper surface of the sensor main body 2a, the wave receiving portion 23a vibrates up and down due to its own elasticity at its inner portion, and its vibration amplitude becomes maximum at the central portion. Thereby, the vibration of the largest part of the wave receiving part 23a is transmitted to the sensor main body 2a via the propagation part 26.

Then, the sound wave propagates from left to right in FIG. 2 while vibrating each of the cantilever resonators 25 whose length is gradually increased (the resonance frequency is sequentially reduced). . Each resonator 25 has a unique resonance frequency, and each resonator 25 resonates when a sound wave of the unique frequency propagates, and its tip vibrates up and down. Due to this vibration, the capacitance of the capacitor formed between the tip and the electrode 3 changes.

The obtained change in capacitance is sent to the detection circuit 4. FIG. 4 is a timing chart in the detection circuit 4. The clock pulse φ ₀ supplied to the operational amplifier 41, the integrating circuit 43, and the sample and hold circuit 44,
φ ₁ and φ ₂ are shown. Note that the clock pulse control in this example is turned on at a low level.

First, in the detection circuit 4, the operational amplifier 41
Of the capacitor obtained in the step C_sAnd reference capacity C_fWith
The amplification ratio is determined according to the impedance ratio. For example, 1 /
ωC _f1 / ωC for (ω = 2πf, f: frequency)_s
Is 1/2, the obtained voltage signal is doubled.
become. However, the operational amplifier 41 has its + input terminal connected.
Because it is an inverting amplifier that is grounded, the next stage operational amplifier
At 41, the voltage phase is inverted by one time. Obtained amplified voltage
The signal is input to the integrating circuit 43. In the integrating circuit 43,
Clock pulse φ₁Within the specified time according to
Voltage V_refThe higher amplified voltage signal is integrated and the integrated
The signal is input to the sample and hold circuit 44. Sump
In the hold circuit 44, the clock pulse φ_TwoIn response to the
Repeat sampling and holding of the integrated signal
Outputs the integration signal to

The above processing is performed in parallel for each of the detection circuits 4 corresponding to the resonators 25 having different lengths. Note that the clock pulses φ ₀ ,
The periods of φ ₁ and φ ₂ are merely examples, and the period of each clock pulse may be set arbitrarily.

As described above, by examining the output signal of the detection circuit 4 corresponding to the resonators 25, 25,... Resonating at a specific frequency, the sound of the specific frequency having an arbitrary time period is obtained. Of the strength over time can be known. Further, by examining the output signals of the detection circuit 4 corresponding to the plurality of resonators 25, 25,..., It is possible to know the temporal change of the sound intensity for each of a plurality of frequency bands with an arbitrary time period. it can. In this case, the integration result may be output for each one specific frequency, or the integration result may be output for each of a plurality of specific frequencies.

Even if the audio data is divided at regular intervals, there is no missing sound data anywhere. In addition, since acoustic data for each frequency is obtained at regular time intervals, it is possible to check the transition of the intensity of each frequency as time elapses, for example, to more accurately determine the temporal change between vowels and consonants. In addition, the discrimination rate of voice recognition can be increased. In addition, since sound data for each frequency can be obtained at regular time intervals, it is possible to check the transition of the intensity of each frequency as time elapses, and it is possible to more accurately determine the temporal change in speech, and to perform speech recognition. This can contribute to increasing the discrimination rate.

FIG. 5 is a diagram showing the relationship between the respective detection circuits 4 corresponding to a specific frequency. Eg, n type of the resonance frequency _{f 1, f 2, f 3} , f 4, ..., in the case where the f _n respectively selectively provide a total 2n book resonator by two each to respond vibration, the 2 corresponding to the resonance intensity for each resonance frequency
n output signals V _1a , V _1b , V _2a , V _2b , V _3a , V _3b ,
V _4a , V _4b ,..., V _na , V _nb can be obtained from each detection circuit 4. In this example, since two detection systems are provided for one resonance frequency, the detection accuracy is higher than when only one detection system is provided. By providing the resonators 25 on only one side of the holder 22, a low-cost acoustic sensor with a further simplified configuration can be provided.

For example, when the acoustic sensor according to the present invention is used as a voice input microphone for voice recognition, the intensity of each frequency is determined according to the resonance intensity at each resonance frequency in the audible band. Recognize speech based on the analysis pattern.

When it is desired to obtain the intensity of only an arbitrarily selected frequency of a sound wave, only the output signal of the detection circuit corresponding to the required resonance frequency may be obtained. For example, when the intensities of the frequencies f ₁ and f ₃ are obtained in FIG. 5, the other detection circuits 4-2a, 4-2b, and 4-4 that do not correspond
a, 4-4b, ..., 4-na, 4-nb
These detection circuits 4-2a, 4-2b, 4-4a, 4-4
b, ..., 4-na, 4-nb
The necessary output signals V _1a , V _1b , V _3a , V _3b are obtained, and the unnecessary output signals V _2a , V _2b , V _4a , V _4b ,..., V _na , V _nb
Should not be obtained. As an example of use of such an acoustic sensor, an abnormal sound input microphone for detecting an abnormal sound of one or more specific frequencies is preferable.

(Second Embodiment) FIG. 6 is a front view showing a configuration of a main part of a second embodiment of an acoustic sensor according to the present invention, and a sectional view taken along line VI-VI of FIG. In the acoustic sensor according to the present embodiment, the left-right dimension of the sensor main body 2a in the first embodiment is substantially halved, and the remaining half is defined as the sensor main body 2b in the present embodiment. The wave receiving portion 23b of a size that covers the entirety of the resonance portion 21 and the holding portion 22 occupying the portion is
Is provided on the upper surface.

With such a configuration, the receiving sensitivity is reduced by half the size of the receiving section 23b as compared with the first embodiment, but the receiving sensitivity is at least equal to or higher than that of the conventional configuration. Sensitivity is obtained. In addition, the size of the entire acoustic sensor is reduced to half, and downsizing of the entire acoustic sensor can be achieved while maintaining the conventional detection sensitivity.

In addition, with the above-described configuration,
The propagation section 26 is arranged near the edge of the wave receiving section 23b. However, in the present embodiment, the wave receiving unit 23
b is not in a fixed state as in the first embodiment, but in a state in which it is substantially placed on the sensor main body 2b, whereby the wave receiving portion 23b moves up and down according to its own elasticity. Not only does it vibrate, but the entire wave receiving portion 23b vibrates up and down, so that a larger vibration amplitude can be obtained.
Thereby, the detection sensitivity can be improved.

It should be noted that an elastic body is interposed at a portion where the wave receiving portion 23b and the sensor main body 2b are in contact with each other, so that the wave receiving portion 2b is provided.
3b does not jump over the sensor body 2b, but vibrates up and down according to the elastic deformation of the elastic body, so that the shock stress between the wave receiving portion 23b and the sensor body 2b can be buffered. .

In the above example, the plurality of resonators 2
The specific resonance frequency band at 5, 25,.
The range is set to 20 kHz, but this is merely an example, and it goes without saying that another frequency range may be used. However, since it is a sound wave, its frequency range is several Hz to 50 kHz (up to 100 kHz at the maximum).

[0056]

As described above in detail, in the acoustic sensor according to the present invention, a sound wave propagated through a medium is received by a wave receiving unit, and the received sound wave is given to a plurality of resonators resonating at different frequencies. By providing at least one of the plurality of resonators and the wave receiving unit of the acoustic sensor having a configuration in which the vibration in each resonator is detected by the vibration intensity detection unit,
The detection sensitivity can be improved without increasing the size of the whole acoustic sensor.

Further, by connecting a holding portion for connecting and holding the plurality of resonators to the wave receiving portion at a central portion of the wave receiving portion, the vibration of the wave receiving portion formed of, for example, a diaphragm is the largest. The vibration can be transmitted to the holding section at the portion, and the wave receiving section can be used most efficiently. Therefore, larger vibration can be transmitted from the wave receiving unit to the holding unit than in the conventional configuration in which the holding unit is in contact with the side surface of the wave receiving unit, and the detection sensitivity can be further improved. . If the conventional detection sensitivity is maintained, the size of the wave receiving unit itself can be reduced.

Further, by supporting the wave receiving portion movably, the vibration of the wave receiving portion can be maintained even when the holding portion is not in the vicinity of the center of the wave receiving portion but in contact with other portions. Can be efficiently transmitted to the holding unit, and also in such a case, the detection sensitivity can be improved.

Further, by holding the wave receiving section,
When the holding section is in contact with the vicinity of the center of the wave receiving section, the entire vibration of the wave receiving section can be efficiently transmitted to the holding section, and the detection sensitivity is improved in such a case. be able to.

Further, by supporting the wave receiving portion via an elastic body, when the holding portion is not in the vicinity of the central portion of the wave receiving portion but is in contact with other portions, the holding portion is not affected by the wave receiving portion. The present invention has excellent effects, such as being able to achieve a floating holding state.

[Brief description of the drawings]

FIG. 1 is a front view showing a configuration of a main part of an acoustic sensor according to a first embodiment of the present invention, and a sectional view taken along a line II of FIG.

FIG. 2 is a perspective view for explaining the operation principle of the acoustic sensor according to the present invention.

FIG. 3 is a block diagram showing a configuration of a detection circuit of the acoustic sensor according to the present invention.

FIG. 4 is a timing chart in the detection circuit of the acoustic sensor according to the present invention.

FIG. 5 is a diagram illustrating a relationship between respective detection circuits corresponding to a specific frequency.

FIG. 6 is a front view showing a configuration of a main part of a second embodiment of the acoustic sensor according to the present invention, and a sectional view taken along line VI-VI of FIG.

FIG. 7 is a plan view showing a configuration of a main part of the disclosed acoustic sensor, and a sectional view taken along line VII-VII of FIG.

[Explanation of symbols]

 2a, 2b Sensor main body 21 Resonant part 22 Holding part 23a, 23b Wave receiving part 25 Resonator 26 Propagation part

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01H 11/02 G10L 11/00

Claims (5)

(57) [Claims] 1. A plate-like wave receiving portion for receiving a sound wave propagating in a medium, a plurality of resonators each resonating at a different frequency of the sound wave received by the wave receiving portion, and a vibration in which each resonator resonates. An acoustic sensor, comprising: a vibration intensity detecting unit that detects intensity; wherein at least one of the plurality of resonators and a wave receiving unit are provided in a stacked manner. 2. The method according to claim 2, wherein the wave receiving unit and a plurality of resonators are connected.
2. The device according to claim 1, further comprising: a holding unit that holds the plurality of resonators, wherein the holding unit is connected at a central portion of the wave receiving unit.
An acoustic sensor as described. 3. The acoustic sensor according to claim 1, further comprising: a supporting portion that supports the wave receiving portion in a freely movable manner. 4. The acoustic sensor according to claim 1, further comprising a holding section for holding the wave receiving section. 5. The acoustic sensor according to claim 3, wherein the support section supports the wave receiving section via an elastic body.