JP5304492B2 - Acoustic transducer - Google Patents

Description

  The present invention relates to an acoustic transducer (electroacoustic transducer) that emits sound waves in the air or water, and more particularly to an acoustic transducer that can efficiently emit sound waves at a low frequency.

  Acoustic transducers that emit sound waves in a medium such as water are used in fields such as ocean observation. The lower the frequency of the sound wave used, the less the attenuation, the better the propagation characteristics, and the better the acoustic radiation can be done over long distances. In recent years, much of the medium such as water around the acoustic radiation surface has been eliminated. Therefore, acoustic transducers that emit low-frequency sound waves have been put into practical use.

  As a conventional acoustic transducer used in water, many systems such as a bolted Langevin transducer, a cylindrical transducer, a flexural transducer, a bent disk transducer, and a barrel stave transducer are currently used.

According to Non-Patent Document 1, a bolted Langevin transducer (also referred to as a Tonpilz type transducer) 101 shown in FIGS. 9A and 9B is a transducer module 103 including a plurality of annular piezoelectric transducers 102. An acoustic radiation plate 104 is provided on one of the end faces. The transducer module 103 itself radiates sound from the acoustic radiation plate 104 using a vibration mode in which a half wavelength is vibrated longitudinally.
Further, the cylindrical transducer 111 shown in FIGS. 10A and 10B is provided with an acoustic radiation plate 114 on the outer peripheral surface of the cylindrical vibrator 112. Then, acoustic radiation is emitted from the acoustic radiation plate 114 using a respiratory vibration mode in the radial direction of the cylindrical vibrator 112 itself, that is, a mode in which longitudinal vibration of one wavelength is formed on the circumferential length of the cylinder.

In addition, the flexural transducer 121 shown in FIGS. 11A and 11B does not directly radiate sound waves into water using the resonance of the vibrator itself, but the cross section of the vibration of the vibrator 122 The bending acoustic radiation plate 124 using an elliptical elliptic shell is converted into a bending vibration to increase the amplitude, and the flexural vibration of the bending acoustic radiation plate 124 is used to radiate the displacement generated by the vibrator 122. .
Further, according to Patent Document 1, the bending disk type transducer 131 shown in FIG. 12 uses a flexural resonance of the bending acoustic radiation plate 134 by bonding a disk-shaped vibrator 132 to the bending acoustic radiation plate 134. Thus, the displacement generated by the vibrator 132 is acoustically radiated.
These acoustic transducers 121 and 131 can eliminate a large amount of medium by using the flexural acoustic radiation plates 124 and 134 using flexural vibrations that can easily obtain a resonance frequency at a frequency lower than that of longitudinal vibrations.

  According to Patent Document 2, the barrel stave transducer 141 shown in FIG. 13 has a plurality of bent acoustic radiation plates 144 arranged on the outer peripheral portion, and a gap d1 between adjacent acoustic radiation plates 144. Is provided.

On the other hand, an electrodynamic speaker (acoustic transducer) that is generally used in the air transmits the vibration of a coil that vibrates due to electromagnetic force to cone paper, and emits sound from the cone paper.
In acoustic radiation to the air, since the acoustic radiation impedance is small, it is possible to secure a large medium excluded volume with a lightweight material such as paper.

JP-A-5-344582 US Pat. No. 4,922,470

“Basics and Applications of Ocean Acoustics (Edited by the Ocean Acoustics Society)”, Naruyamado Shoten, April 28, 2004, p. 58-60

However, the conventional acoustic transducer has the following problems.
In order to increase the medium excluded volume in the bolted Langevin transducer 101 shown in FIG. 9 and the cylindrical transducer 111 shown in FIG. 10, it is necessary to increase the displacement of the acoustic radiation plate by increasing the length and diameter of the vibrator. However, there is a problem that the size of the acoustic transducer itself increases and the weight increases. Therefore, at present, these acoustic transducers are used at a frequency of approximately 1 kHz or more due to limitations on dimensions and the like.

Further, in order to increase the medium excluded volume in the flexural transducer 121 shown in FIG. 11 and the bent disk transducer 131 according to Patent Document 1 shown in FIG. 12, it is necessary to increase the area of the acoustic radiation plate, In this case as well, the size of the acoustic transducer itself increases and the weight increases.
In particular, when a piezoelectric ceramic having a large mass is used for the flexural vibration plate, a structure having a large mass at a location with a large amplitude is obtained, and a low resonance frequency can be obtained. There is a problem that the degree of sharpness is high and it is not suitable for acoustic radiation in a wide band.

In addition, since the barrel stave transducer 141 shown in FIG. 13 needs a gap between adjacent acoustic radiation plates, when the whole is molded for watertightness, the vibration of the gap d1 is hindered by water pressure, and the efficiency of acoustic radiation is improved. There was a decline.
Also, electrodynamic speakers used in the air use larger cone paper in order to increase the medium excluded volume, resulting in an increase in speaker size. Also, in the case of a method of acoustic emission by attaching a piezoelectric vibrator to a diaphragm like a piezoelectric speaker, it is necessary to increase the diameter of the diaphragm in order to increase the medium excluded volume.

  Moreover, when an acoustic transducer is equipped on an underwater vehicle or towed vehicle, the specific gravity is desired to be close to or rather small as that of the medium (water). When the specific gravity is larger than the medium, a buoyancy material is required for floating the acoustic transducer in the case of an underwater vehicle, and the acoustic transducer hangs down in the case of a towing vehicle that does not have a space for providing a buoyancy body. Conventional acoustic transducers capable of low-frequency acoustic radiation have a high proportion of piezoelectric ceramics used as vibrators, and their specific gravity is 1 or more.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an acoustic transducer that can efficiently eliminate a medium around the acoustic radiation plate without increasing the shape of the vibrator or the acoustic radiation plate. And

  In order to achieve the above object, an acoustic transducer according to the present invention is an acoustic transducer that radiates sound waves in the air or in water. An axial member that extends to the center of the acoustic transducer, and an axial direction around the axial member. And an even number of four or more channels arranged in the same manner, an acoustic radiation plate in a shape obtained by dividing a cylinder disposed between adjacent channels in the radial direction, the shaft member and the channel, and a vibrator The acoustic radiation plate that curves in a direction approaching the shaft member and the acoustic radiation plate that curves in a direction away from the shaft member are alternately arranged.

  According to the present invention, the medium around the sound radiation surface can be efficiently removed without increasing the size of the sound radiation plate or the vibrator, so that low-frequency sound radiation can be achieved and the acoustic transducer can be downsized. can do.

(A) is a figure which shows an example of the acoustic transducer by 1st embodiment of this invention, (b) is the sectional view on the AA line of (a). (A), (b) is a figure explaining operation | movement of the acoustic transducer shown in FIG. (A) thru | or (c) is a figure which shows the arrangement | positioning method of the piezoelectric vibrator by 1st embodiment. It is a figure which shows an example of the acoustic transducer by 2nd embodiment. (A), (b) is a figure which shows the arrangement | positioning method of the piezoelectric vibrator by 2nd embodiment. It is a figure which shows an example of the acoustic transducer by 3rd embodiment. (A) is a figure which shows an example of the acoustic transducer by 4th embodiment, (b) is the BB sectional drawing of (a). It is a figure which shows an example of the acoustic transducer by 5th embodiment. (A) is a figure which shows the conventional bolting Langevin type acoustic transducer, (b) is CC sectional view taken on the line of (a). The figure which shows the conventional cylindrical acoustic transducer, (b) is the DD sectional view taken on the line of (a). The figure which shows the conventional flexural type acoustic transducer, (b) is the EE sectional view taken on the line of (a). The figure which shows the conventional bending disk type | mold acoustic transducer, (b) is the FF sectional view taken on the line of (a). The figure which shows the conventional barrel stave type | mold acoustic transducer, (b) is the GG sectional view taken on the line of (a).

Hereinafter, an acoustic transducer according to a first embodiment of the present invention will be described with reference to FIGS.
As shown in FIG. 1A, the acoustic transducer 1a according to the first embodiment has eight channels 3 arranged in the same axial direction around a shaft (shaft member) 2 extending in the center. It is installed. The shaft 2 is formed longer in the axial direction than the channel 3, and the tip 2 a of the shaft 2 and the tip 3 a of each channel 3 are connected by a connecting member 4.
Between the channels 3 adjacent to each other in the circumferential direction around the shaft 2, first and second acoustic radiation plates 5 and 6 are alternately arranged.

  The first and second acoustic radiation plates 5 and 6 are members that have flexibility and radiate sound waves to a medium M such as water. The first acoustic radiation plate 5 is curved outward in the radial direction (medium M side) when disposed between the adjacent channels 3 or the connecting members 4. The second acoustic radiation plate 6 is curved radially inward (on the shaft 2 side) when disposed between the adjacent channels 3 or the connecting members 4. Here, the first and second acoustic radiation plates 5 and 6 will be described below with the shaft 2 side as the inner side and the medium M side as the outer side.

Further, between the adjacent connecting members 4, the curvature radius of the third acoustic radiation plate 5a, the second acoustic radiation plate 6 and the bottom surface which form a partial conical surface having the same curvature radius as that of the first acoustic radiation plate 5 and the bottom surface. The fourth acoustic radiation plates 6a having the same partial conical surface are alternately arranged.
The first, second, third, and fourth acoustic radiation plates 5, 6, 5a, and 5b are formed of a synthetic resin or a material containing a synthetic resin, and are members having a honeycomb structure.

As shown in FIG. 1B, a plate-like bending vibration plate 7 is disposed radially around the shaft 2, and the bending vibration plate 7 is connected to the shaft 2 and the channel 3. A plate-like piezoelectric vibrator (vibrator) 8 is bonded to one surface of the bending vibration plate 7. The bending vibration plate 7 and the piezoelectric vibrator 8 form a bending vibration module 9 having a unimorph structure.
The bending diaphragm 7 is connected to the first and second acoustic radiation plates 5 and 6 through the channel 3.
The channel 3 and the bending diaphragm 7 are formed of a synthetic resin or a material containing a synthetic resin, and are formed as a member having a honeycomb structure or a laminated structure. The channel 3 may be formed of a material with high density such as metal or ceramic.
The entire acoustic transducer 1a thus configured is molded with a synthetic resin (not shown) and is electrically insulated from a medium M such as surrounding water. The material of the mold is not limited to the synthetic resin, and the material and thickness of the mold may be set optimally depending on the required water pressure resistance.

Next, the operation of the acoustic transducer 1a according to the first embodiment will be described.
As shown in FIGS. 2A and 2B, when the piezoelectric vibrator 8 receives a predetermined applied voltage, a displacement to expand and contract occurs. Since the piezoelectric vibrator 8 is bonded to the bending vibration plate 7, the bending vibration plate 7 generates a displacement that bends due to the displacement of the piezoelectric vibrator 8.
Then, when the bending vibration plate 7 is displaced, the channel 3 is displaced, and the first and second acoustic radiation plates 5 and 6 connected to the channel 3 are displaced. The third and fourth acoustic radiation plates 5 a and 6 b disposed between the connecting members 4 are also displaced in accordance with the displacement of the channel 3 that is transmitted via the connecting member 4.

The medium removal by the first and second acoustic radiation plates 5 and 6 will be described with reference to the drawings.
The adjacent first and second acoustic radiation plates 5 and 6 have curved shapes, respectively, and when the interval between the adjacent channels 3 is increased, the curvature (deflection) of the curve is reduced and the adjacent channels are displaced. When the interval 3 becomes smaller, the curvature of curvature (deflection) becomes larger.
Here, when the distance between the channels 3 is increased, the first acoustic radiation plate 5 is displaced in the inward direction in which the curvature of curvature is reduced and the medium exclusion is reduced as shown in FIG. When it becomes narrower, as shown in FIG. 2A, the curvature of the curve increases and the displacement of the medium increases as the medium is removed.
On the other hand, in the second acoustic radiation plate 6, when the distance between the channels 3 is increased, the curvature of the curve is reduced and the displacement of the medium is increased as shown in FIG. Then, as shown in FIG. 2B, the curvature of the curve increases and the displacement in the inward direction reduces the medium exclusion.
At this time, the third and fourth acoustic radiation plates 5a and 6b disposed between the coupling members 4 are also displaced in accordance with the displacement of the channel 3 transmitted through the coupling member 4, and the first and second acoustic waves are displaced. It will be displaced similarly to the radiation plates 5 and 6.

Adjacent bending vibration modules 9 have their bending directions opposite to each other so that the displacement of the end portion on the channel 3 side becomes a displacement approaching and a displacement moving away from each other, and the polarization position of the piezoelectric vibrator 8 and the polarization of the piezoelectric vibrator 8. The direction of the lead wire connecting the piezoelectric vibrator 8 is adjusted.
For example, as shown in FIG. 3A, in the circumferential direction around the shaft 2, the polarization directions of the adjacent piezoelectric vibrators 8 are reversed, and the piezoelectric vibrators 8 are bonded to the bending vibration plates 7. Change the surface to be used alternately.
Further, for example, as shown in FIG. 3B, in the circumferential direction around the shaft 2, the polarization directions of the adjacent piezoelectric vibrators 8 are opposite to each other, and the piezoelectric vibrators 8 with respect to the bending vibration plates 7. The surfaces to be bonded are the same.
Further, for example, as shown in FIG. 3C, in the circumferential direction around the shaft 2, the polarization directions of adjacent piezoelectric vibrators 8 are the same direction, and the piezoelectric vibrators 8 are alternately connected.
By arranging the piezoelectric vibrator 8 in this way, when two adjacent bending diaphragms 7 are displaced and the distance between the channels 3 connected to these bending diaphragms 7 becomes wide, these The bending vibration plate 7 is displaced so as to approach the bending vibration plate 7 disposed next to the other, and the interval between the channels 3 connected to these bending vibration plates 7 is narrowed.

And since the 1st and 2nd acoustic radiation plates 5 and 6 are alternately arrange | positioned between the adjacent channels 3, application of a drive voltage of the 1st and 2nd acoustic radiation plates 5 and 6 is carried out. The direction of medium exclusion is the outward medium exclusion direction as shown in FIG. 2 or the entire inward medium exclusion direction shown in FIG.
At this time, the displacement balance can be maintained by arranging a plurality of flexural vibration modules 9 having the same structure radially so as to be rotationally symmetric with respect to the shaft 2. Since this displacement is repeatedly generated by the driving voltage, it is possible to radiate sound uniformly around the shaft 2.
The first and second acoustic radiation plates 5 and 6 are set to an optimal bending rate in consideration of an acoustic load based on the frequency used.

At this time, the distance between the shaft 2 and the connecting member 4 becomes narrower as it approaches the tip 2a of the shaft 2, thereby gradually changing the displacement of the connecting member 4 and the third and fourth acoustic radiation plates 5a and 6b. Therefore, it is possible to avoid a reduction in displacement in the vicinity of the tip 2a of the shaft 2.
Further, by making the resonance frequency of the bending vibration of the bending vibration module 9 coincide with the resonance frequency of the first and second acoustic radiation plates 5, 6, the displacement and bending of the first and second acoustic radiation plates 5, 6 are achieved. The displacement of the diaphragm 7 can be superimposed, and the electroacoustic conversion efficiency can be further increased.
In addition, the electroacoustic conversion efficiency can be further increased by adopting a structure in which the resonance frequency of the bending vibration module 9 and the first and second acoustic radiation plates 5 and 6 is made to coincide with the radiated acoustic frequency, that is, the frequency of the driving voltage. it can.

Next, the effect of the acoustic transducer according to the first embodiment will be described with reference to the drawings.
In the acoustic transducer 1a according to the first embodiment, the first and third acoustic radiation plates 5, 5a curved outward and the second and fourth acoustic radiation plates 6, 6a curved inward are alternately arranged. Because it emits sound by changing its curvature, the displacement can be expanded compared with conventional acoustic transducers using a flat acoustic radiation plate, a large acoustic exclusion volume can be secured, and low frequency The effect which can implement | achieve acoustic radiation is produced.
In addition, by bonding the piezoelectric vibrator 8 to the bending vibration plate 7, the bending vibration plate 7 bends and vibrates, so that the resonance frequency can be made lower than the longitudinal vibration and the output frequency can be lowered.
Further, the first and second acoustic radiation plates 5 and 6 are curved and are alternately arranged, and the medium is efficiently removed by changing the curvature thereof. It is not necessary to increase the shape of the first and second acoustic radiation plates 5 and 6, and the acoustic transducer 1a can be reduced in weight.

In addition, the first and second acoustic radiation plates 5 and 6 are formed of a synthetic resin or a material containing a synthetic resin to be a honeycomb structure member, which can be a light weight and strength member. The acoustic transducer 1a can be reduced in weight.
In addition, the channel 3 and the flexural diaphragm 7 can be formed as a member that is lightweight and has sufficient strength by using a synthetic resin or a material containing a synthetic resin in a honeycomb structure or a laminated structure. Can be reduced in weight.
Needless to say, the first and second acoustic radiation plates 5 and 6, the flexural vibration plate 7 and the channel 3 may be made of other materials such as metal.

Next, other embodiments will be described with reference to the accompanying drawings. However, the same or similar members and parts as those of the above-described first embodiment are denoted by the same reference numerals, and description thereof is omitted. A configuration different from the embodiment will be described.
As shown in FIG. 4, the acoustic transducer 1 b according to the second embodiment has a piezoelectric vibrator 18 bonded to both sides of each bending vibration plate 17, and is bent by the bending vibration plate 17 and the piezoelectric vibrator 18. A vibration module 19 is configured.
At this time, the polarization direction and connection of the piezoelectric vibrator 18 are adjusted so that the displacement direction of the bending vibration plate 17 adjacent in the circumferential direction around the shaft 12 is opposite.
For example, as shown in FIG. Piezoelectric vibrators having the same polarization direction are disposed on both surfaces of the bending vibration plate 17, and the polarization directions of the piezoelectric vibrators 18 are reversed in adjacent bending vibration plates 17.
Further, for example, as shown in FIG. 5B, piezoelectric vibrators 18 having opposite polarization directions are disposed on both surfaces of the bending vibration plate 17, and the connection directions of these piezoelectric vibrators 18 are reversed and adjacent to each other. In the bending vibration plate 17, the polarization direction of the piezoelectric vibrator 18 is reversed.

  According to the acoustic transducer 1b according to the second embodiment, since the piezoelectric vibrators 18 are bonded to both surfaces of the bending vibration plate 17, the bending vibration plate 17 is more reliably bent and oscillated as compared with the first embodiment. Can be made.

As shown in FIG. 6, the acoustic transducer 1c according to the third embodiment is arranged radially around the shaft 22 instead of the bending vibration module 9 according to the first embodiment, and the shaft 22 and the channel are arranged. 23 is a structure including a displacement magnifying plate 27 having flexibility and a piezoelectric vibrator stack 28 provided in the vicinity of the shaft 2 between the adjacent displacement magnifying plates 27. The displacement enlarging plate 27 is formed of a synthetic resin or a material containing a synthetic resin, and is a member having a honeycomb structure or a laminated structure.
The piezoelectric vibrator stack 28 has a structure in which plate-like piezoelectric vibrators are stacked. When one of the piezoelectric vibrator stacks 28 is expanded, the piezoelectric vibrator stack 28 adjacent to the piezoelectric vibrator stack 28 is contracted. In addition, the polarity of the connecting lines of the piezoelectric vibrators constituting the piezoelectric vibrator stack is alternately reversed, or the polarization direction of the piezoelectric vibrators is reversed. The extending piezoelectric vibrator stack 28 and the shrinking piezoelectric vibrator stack 28 are alternately disposed between the displacement enlarging plates 27.

When the piezoelectric vibrator stack 28 is displaced and stretched, the displacement magnifying plates 27 connected to both ends of the piezoelectric vibrator stack 28 are displaced in a direction away from each other. At this time, since the piezoelectric vibrator stack 28 is disposed in the vicinity of the shaft 22, the end of the displacement magnifying plate 27 on the channel 23 side is displaced more greatly than the expansion and contraction of the piezoelectric vibrator stack 28, and the channel 23 is greatly displaced. Can be made. When the channel 23 is greatly displaced, the vibration of the piezoelectric vibrator stack 28 is expanded and transmitted to the first and second acoustic radiation plates 25 and 26, and the first and second acoustic radiation plates 25 and 26 are transmitted. Can be displaced by greatly changing its curvature to eliminate the medium.
Further, when the piezoelectric vibrator stack 28 is displaced and contracted, the displacement of the piezoelectric vibrator stack 28 is enlarged and transmitted to the first and second acoustic radiation plates 25 and 26.
At this time, by making the resonance frequency of the bending vibration of the displacement magnifying plate 27 coincide with the resonance frequency of the first and second acoustic radiation plates 25 and 26, the electroacoustic conversion efficiency can be further increased. Furthermore, the electroacoustic conversion efficiency can be further increased by adopting a structure in which the resonance frequency of the displacement magnifying plate 27 and the first and second acoustic radiation plates 25 and 26 is made to coincide with the radiated acoustic frequency, that is, the frequency of the driving voltage. it can.

  According to the acoustic transducer 1c according to the third embodiment, since the piezoelectric vibrator stack 28 is provided in the vicinity of the shaft 22 of the displacement magnifying plate 27, the displacement of the piezoelectric vibrator stack 28 is expanded, and Since transmission is performed to the second acoustic radiation plates 25 and 26, medium exclusion by the first and second acoustic radiation plates 25 and 26 can be increased with respect to the displacement of the piezoelectric vibrator stack 28.

As shown in FIGS. 7A and 7B, the acoustic transducer 1d according to the fourth embodiment has end plates 41 provided at both end portions 32a of the shaft 32, and is connected according to the first embodiment. The member is not provided. A buffer material 42 is provided between the end portion 41 a and the end portion 33 a of the channel 33 and the end portions 35 a and 35 b of the first and second acoustic radiation plates 35 and 36. A gap d is provided between the end plate 41 and the bending vibration module 39.
At this time, the hardness and softness of the buffer material 42 and the material and thickness of the mold are optimally set according to the required water pressure resistance.
The acoustic transducer 1d according to the fourth embodiment has the same effects as those of the first embodiment.

As shown in FIG. 8, in the acoustic transducer 1e according to the fifth embodiment, the connecting member according to the first embodiment and the end plate according to the fourth embodiment are not provided, and the first and second acoustic radiations are provided. The medium M is in contact with both surfaces of the plates 55 and 56.
According to the fifth embodiment, the cylindrical portion is constituted by the channel 53 and the first and second acoustic radiation plates 55 and 56, and the water column resonance of the water (medium M) therein is utilized. A container having a small through-hole can be provided inside the cylindrical portion to provide a Helmholtz resonance structure.

  As an application example of the present invention, it can be considered to be used as a transmitter that radiates sound in water or in the air.

As mentioned above, although the embodiment of the acoustic transducer according to the present invention has been described, the present invention is not limited to the above embodiment, and can be appropriately changed without departing from the scope of the present invention.
For example, in the above-described embodiment, eight channels are arranged around the shaft, but the number of channels may be other numbers.
For example, in the above-described embodiment, the first and second acoustic radiation plates are formed of a synthetic resin or a material containing a synthetic resin, and this material is a honeycomb structure member. However, the first and second acoustic radiation plates are formed of other materials. May be.
Further, in the above embodiment, the channel 3 and the bending diaphragm 7 are formed of a synthetic resin or a material containing a synthetic resin, and are formed as a member having a honeycomb structure or a laminated structure, but may be formed of other materials, The member may not be a honeycomb structure or a laminated structure.
In the third embodiment, the displacement enlarging plate 27 is formed of a synthetic resin or a material containing a synthetic resin and has a honeycomb structure or a laminated structure. However, the displacement expansion plate 27 may be formed of other materials. Or a laminated structure.

1a, 1b, 1c, 1d, 1e Acoustic transducer 2, 12, 22, 32, shaft (shaft member)
3, 13, 23, 33, 53 channels
4 connecting member 5, 15, 25, 35, 55 first acoustic radiation plate 5a third acoustic radiation plate 6, 16, 26, 36, 56 second acoustic radiation plate
6a Fourth acoustic radiation plate 7, 17 Bending vibration plate
8, 18 Piezoelectric vibrator (vibrator)
41 End plate 42 Buffer material d Crevice M Medium

Claims (17)

In an acoustic transducer that emits sound waves to a medium such as air or water,
A shaft member extending to the center of the acoustic transducer;
The shaft member as a central axis, and a channel disposed at intervals in the circumferential direction;
A first acoustic radiation plate and a second acoustic radiation plate arranged alternately between the channels adjacent in the circumferential direction; and a plurality of plate members connected to the shaft member and the channel and provided with a vibrator. The acoustic radiation plate is curved outward in a cross section in a plane intersecting the axis of the shaft member, and the second acoustic radiation plate is curved inward in a cross sectional shape in a plane intersecting the axis of the shaft member. An acoustic transducer characterized by.   The acoustic transducer according to claim 1, wherein the vibrator displaces the adjacent bending diaphragms in opposite directions.   The shaft member is formed longer than the channel, and is provided with a plurality of connecting members that respectively connect the tip end portions of the shaft member and the tip ends of the plurality of channels, and between adjacent connecting members in the circumferential direction. And a third acoustic radiation plate having a partial conical surface having the same curvature radius as the bottom surface of the first acoustic radiation plate, and a partial conical surface having the same curvature radius as the second acoustic radiation plate and the bottom surface. The acoustic transducer according to claim 1, further comprising a fourth acoustic radiation plate.   4. The acoustic transducer according to claim 3, wherein the third and fourth acoustic radiation plates are made of a synthetic resin or a material containing a synthetic resin.   5. The acoustic transducer according to claim 3, wherein the third and fourth acoustic radiation plates are formed of a honeycomb structure material.   End plates are provided at both ends of the shaft member, a buffer material is provided between the channel and the acoustic radiation plate, and the end plate, and the plate member and the end plate are separated from each other. The acoustic transducer according to claim 1, wherein the acoustic transducer is provided.   The acoustic transducer according to claim 1, wherein the plate member is a flexural vibration plate including the vibrator on one side.   The acoustic transducer according to claim 1, wherein the plate member is a flexural vibration plate having the vibrator on both sides.   The acoustic transducer according to claim 1, further comprising a vibrator that connects the plate members between the adjacent plate members.   The acoustic transducer according to claim 1, wherein a resonance frequency of the plate member due to the displacement of the vibrator is equal to a resonance frequency of the acoustic radiation plate.   The acoustic transducer according to any one of claims 1 to 10, wherein the first and second acoustic radiation plates are made of a synthetic resin or a material containing a synthetic resin.   The acoustic transducer according to any one of claims 1 to 11, wherein the first and second acoustic radiation plates are formed of a honeycomb structure material.   The acoustic transducer according to claim 1, wherein the plate member is made of a synthetic resin or a material containing a synthetic resin.   The acoustic transducer according to any one of claims 1 to 13, wherein the plate member is formed of a material having a honeycomb structure or a laminated structure.   The acoustic transducer according to claim 1, wherein the channel is formed of a synthetic resin or a material containing a synthetic resin.   16. The acoustic transducer according to claim 1, wherein the channel is formed of a material having a honeycomb structure or a laminated structure.   The acoustic transducer according to claim 1, wherein the channel is made of metal or ceramic.

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