JP5446134B2 - Sound absorbing structure - Google Patents

Description

  The present invention relates to a technique for absorbing sound.

  As in the sound absorbing structure disclosed in Patent Document 1, a sound absorbing structure that absorbs sound by a plate-like (or film-like) vibrating body and an air layer behind the vibrating body (hereinafter referred to as a plate / membrane vibrating type sound absorbing structure) Called). In this plate / membrane vibration type sound absorption structure, a sound absorption mechanism of a spring mass system is formed by the mass component of the vibrating body and the spring component of the air layer, and the sound is absorbed.

JP 2006-11412 A

  By the way, in the plate / membrane vibration type sound absorbing structure, the frequency of the sound to be absorbed can be changed by changing the thickness of the air layer or the material of the vibrating body. However, since the frequency band with a high sound absorption rate is narrow, there is a problem that sound cannot be efficiently absorbed in a wide band.

  The present invention has been made under the above-described background, and an object of the present invention is to provide a technique for efficiently absorbing sound by expanding a frequency band having a high sound absorption coefficient in a plate / membrane vibration type sound absorbing structure.

In order to solve the above-described problem, the present invention has a plurality of plate-like or membrane-like vibrators and a side wall in the shape of a tube having a hollow portion, and the vibrator has the above-described shape so as to close the hollow portion. The sound absorbing structure fixed to the side wall, wherein the plurality of vibrators are arranged non-parallel, the surface faces the surface of another vibrator at a distance, and the vibrators and air layers are alternately stacked. I will provide a.

In the present invention, the number of the vibrators may be three or more.
In the present invention, the plurality of vibrators may have different thicknesses.
In the present invention, the air layer may have a porous sound absorbing material.
In the present invention, the non-vibrating body having higher rigidity than the vibrating body faces one of the two outermost vibrating bodies among the plurality of vibrating bodies that alternately overlap the air layer. May be.

  According to the present invention, in a plate / membrane vibration type sound absorbing structure, it is possible to efficiently absorb sound by expanding a frequency band having a high sound absorption coefficient.

[First Embodiment]
FIG. 1 is an external view of a sound absorbing structure 1 according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the sound absorbing structure 1, and FIG. 3 is a cross-sectional view taken along the line AA of the sound absorbing structure 1. is there. In the drawings, the dimensions of the sound absorbing structure 1 are different from the actual dimensions in order to illustrate the configuration of the present embodiment in an easy-to-understand manner.

(Configuration of each part)
The sound absorbing structure 1 is roughly composed of a housing 10, a first vibrating body 20-1, and a second vibrating body 20-2 as shown in the figure.
A casing 10 formed of a metal plate has a square plate-like bottom surface portion 11 and a side wall 12 having a square tube shape and a square cross-sectional shape. In the present embodiment, the housing 10 is made of metal, but the material is not limited to metal, and supports the first vibrating body 20-1 and the second vibrating body 20-2 to support the first vibration. Other materials such as a synthetic resin other than metal, a wood material, and a fiber board may be used as long as the body 20-1 and the second vibration body 20-2 cause vibration.

  The 1st vibrating body 20-1 makes polyethylene thin film shape, and the shape is a square. The first vibrating body 20-1 has elasticity, deforms when a force (sound pressure) is applied, and vibrates by generating a restoring force by elasticity. In the present embodiment, the material of the first vibrating body 20-1 is polyethylene, but the material is not limited to polyethylene. If the material has elasticity and vibration occurs, synthetic resin other than polyethylene, paper, metal Other materials such as fiberboard may be used.

  The second vibrating body 20-2 is a plate of ABS (Acrylonitrile: acrylonitrile, Butadiene: butadiene, Styrene: styrene copolymer synthetic resin) resin. The second vibrating body 20-2 has a square shape, and the area thereof is the same as the cross-sectional area of the hollow portion of the side wall 12. The second vibrating body 20-2 also has elasticity, deforms when a force (sound pressure) is applied, and vibrates by generating a restoring force by elasticity. In the present embodiment, the material of the second vibrating body 20-2 is ABS resin, but the material is not limited to ABS resin. If the material has elasticity and vibration occurs, synthetic resin other than ABS resin, Other materials such as paper, metal, and fiberboard may be used.

(overall structure)
In the sound absorbing structure 1, the bottom surface portion 11 is fixed to one (back side) opening portion of the side wall 12, and the first vibrating body 20-1 is fixed to the other (front side) opening portion, so The vibrating body 20-1 is parallel. Further, the second vibrating body 20-2 is parallel to the bottom surface portion 11 at a position that is a predetermined distance from the bottom surface portion 11 toward the first vibrating body 20-1 side inside the side wall 12, and the second vibrating body 20-2 is parallel to the side wall 12. It is fixed to.

As a result, the first air surrounded by the first vibrating body 20-1, the side wall 12, and the second vibrating body 20-2 and partitioned in the shape of a rectangular parallelepiped immediately behind the first vibrating body 20-1. A layer 30-1 is formed, and is surrounded by the second vibrating body 20-2, the side wall 12, and the bottom surface portion 11, and is partitioned into a rectangular parallelepiped shape immediately behind the second vibrating body 20-2. A second air layer 30-2 is formed.
In addition, in this embodiment, although the 1st air layer 30-1 and the 2nd air layer 30-2 are sealed, the hole is provided in the side wall 12 or the bottom face part 11, and the 1st air layer 30-1 or the 2nd air is provided. The layer 30-2 may communicate with the space outside the sound absorbing structure 1.

In the sound absorbing structure 1 configured as described above, the mass component of the first vibrating body 20-1, the mass component of the second vibrating body 20-2, the spring component of the first air layer 30-1, and the second air layer. As shown in the following (1) to (5), the sound absorbing mechanism of the sound absorbing structure 1 is formed by a plurality of spring mass sound absorbing mechanisms individually or in combination with each other by the spring component 30-2.
(1) A sound absorbing mechanism formed by the first vibrating body 20-1 and the first air layer 30-1.
(2) A sound absorbing mechanism formed by the second vibrating body 20-2 and the second air layer 30-2.
(3) A sound absorbing mechanism formed by an air layer in which the first vibrating body 20-1 is integrated with the first air layer 30-1 and the second air layer 30-2.
(4) A sound absorbing mechanism formed by the second vibrating body 20-2 and the first air layer 30-1.
(5) A sound absorbing mechanism formed by the first vibrating body 20-1, the second vibrating body 20-2, and the second air layer 30-2.
Further, the first vibrating body 20-1 and the second vibrating body 20-2 have elasticity, and when these vibrating bodies vibrate, the bending sound absorption mechanism by bending vibration (natural vibration) is also provided. It is formed. In the present embodiment, the bottom surface portion 11 and the housing 10 have higher rigidity than the first vibrating body 20-1 and the second vibrating body 20-2, and function as non-vibrating members (non-vibrating bodies). .

  Here, in each of the sound absorption mechanisms (1) to (5), a peak of the sound absorption coefficient appears for each sound absorption mechanism, but each sound absorption mechanism has a different mass component or spring component. The frequency of is also different for each sound absorption mechanism. That is, in the sound absorbing structure 1, the sound absorption coefficient peaks appear at a plurality of frequencies, and sound is efficiently absorbed in a wide band.

  FIG. 4 is a graph ((2) in FIG. 4) showing the measurement result of the octave analysis (1/3 octave band) of the normal incident sound absorption coefficient of the sound absorbing structure 1 (measurement of the normal incident sound absorption coefficient is JIS A 1405-2 (Acoustic tube sound absorption coefficient and impedance measurement-Part 2: Transfer function method). In the measurement of the sound absorption coefficient, the sound absorbing structure 1 has a thickness of the first vibrating body 20-1 of 0.85 [mm] and a first air layer 30-1 as shown in FIG. The thickness is 30 [mm], the thickness of the second vibrating body 20-2 is 3 [mm], the thickness of the second air layer 30-2 is 30 [mm], and the first vibrating body 20- 1 is set to be smaller than the surface density of the second vibrating body 20-2, and the resonance frequency of the first vibrating body 20-1 on the front side on which the sound wave enters is the resonance frequency of the second vibrating body 20-2 on the back side. It is set relatively higher.

For comparison, in FIG. 4, the normal incident sound absorption of other sound absorbing structures (FIGS. 5B and 5C) that do not include the second vibrating body 20-2 and the second air layer 30-2. A graph of the rate measurement results is also shown.
The sound absorbing structure shown in FIG. 5B does not include the second vibrating body 20-2, the thickness of the first vibrating body 20-1 is 0.85 [mm], and the first vibrating body 20-1 The thickness of the air layer behind is 30 [mm], and the sound absorbing structure shown in FIG. 5C does not include the second vibrating body 20-2, and the material of the first vibrating body 20-1 is ABS. Instead of resin, the thickness is 3 [mm], and the thickness of the air layer behind the first vibrating body 20-1 is 30 [mm].

  In the case of the sound absorbing structure shown in FIG. 5B, when the sound absorbing mechanism is formed by the mass component of the first vibrating body 20-1 and the spring component of the air layer, and the sound wave reaches the first vibrating body 20-1. Sound is absorbed. The graph of (1) in FIG. 4 shows the measurement result of the sound absorbing structure shown in FIG. 5B. In this sound absorbing structure, the sound absorption coefficient peak is in the vicinity of 400 [Hz]. On the other hand, at 250 [Hz] or less, the sound absorption coefficient is low, and it can be seen that sound absorption cannot be performed in a wide band.

  In the case of the sound absorbing structure shown in FIG. 5C, the graph of FIG. 4C is the measurement result of the sound absorbing structure shown in FIG. 5C. In this sound absorbing structure, The peak of the sound absorption coefficient appears in the vicinity of 250 [Hz], but the sound absorption coefficient is low at frequencies higher or lower than this. That is, it can be seen that although sound absorption can be performed in the vicinity of 250 [Hz], the sound absorption rate is low in other frequency bands and sound absorption cannot be performed in a wide band.

  On the other hand, in the case of the sound absorbing structure 1 according to the present embodiment shown in FIG. 5A, a peak of the sound absorption coefficient appears near 235 [Hz] as shown in the graph of FIG. 4B. Even at 315 [Hz] or higher, a sound absorption coefficient equivalent to that of the sound absorbing structure shown in FIG. 5B is obtained. Therefore, as shown in FIG. 5B and FIG. 5C, compared with a sound absorbing structure in which the vibrating body and the air layer are one, a wide frequency including the sound absorption characteristics of FIG. 5B and FIG. 5C. It can be seen that sound is absorbed by the belt.

In addition, the boundary surfaces of various panels that make up the cabin in automobiles, rooms such as general houses, building conference rooms and living rooms, soundproof rooms, music rooms, halls, theaters, acoustic rooms such as listening rooms for audio equipment, etc. When the first vibration body 20-1 of the sound absorbing structure 1 is directed to the sound field on the boundary surfaces (walls, floors, ceilings, etc.) of various rooms, Sound waves other than the resonance frequency of the vibrating body are divided into, for example, components that pass through each vibrating body and components that are reflected by each vibrating body as shown in (a) to (d) below.
(A) A reflected wave reflected by the first vibrating body 20-1.
(B) A reflected wave that passes through the first vibrating body 20-1, is reflected by the second vibrating body 20-2, and passes through the first vibrating body 20-1.
(C) A reflected wave that passes through the first vibrating body 20-1 and the second vibrating body 20-2, is reflected by the bottom surface portion 11, and passes through the second vibrating body 20-2 and the first vibrating body 20-1.
(D) After passing through the first vibrating body 20-1, reflected by the second vibrating body 20-2, reflected again by the first vibrating body 20-1, and then reflected again by the second vibrating body 20-2. The reflected wave which permeate | transmits the 1st vibrating body 20-1.
These reflected waves are gradually shifted in phase and reach the sound field. Then, in the sound field where these reflected waves that are out of phase are superimposed, the bias of the sound pressure distribution (standing wave) is alleviated, reducing not only the sound absorption but also the noise in the rooms such as the vehicle compartment and the acoustic room. You can also It is also possible to improve sound quality such as audio, musical sound, and voice.

  Also, in a cabin with a relatively small volume, various noises (road noise, wind noise, engine noise, etc.) are incident, so that an isolated natural vibration mode is easily excited in the cabin, and noise is generated in a specific frequency band. However, when a reflected wave that is gradually shifted in phase is formed by the sound absorbing structure 1 and re-enters the vehicle interior, the isolated natural vibration mode in the vehicle interior is relaxed, so that the vehicle interior noise is reduced. You can also.

  In the sound-absorbing structure 1, a porous sound-absorbing material such as glass wool, felt, foamed polyurethane, and nonwoven fabric is disposed in the first air layer 30-1 or the second air layer 30-2, and the above-described spring mass-based sound absorbing mechanism. The sound absorbed by the sound may be absorbed in a wider band.

[Second Embodiment]
Next, the sound absorbing structure 1A according to the second embodiment of the present invention will be described.
Similar to the sound absorbing structure 1 of the first embodiment, the sound absorbing structure 1 </ b> A includes a housing 10 including a bottom surface portion 11 and a side wall 12, a first vibrating body 20-1, and a second vibrating body 20-2. The appearance is the same as that of the sound absorbing structure 1 of the first embodiment. The sound absorbing structure 1A is different from the sound absorbing structure 1 of the first embodiment in that it has a plurality of vibrating bodies inside the side wall 12 as shown in FIG. 6 (cross-sectional view of the sound absorbing structure 1A). It is. In the drawings, the dimensions of the sound absorbing structure 1 are different from the actual dimensions in order to illustrate the configuration of the present embodiment in an easy-to-understand manner. In the description below, members having the same configurations as those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed descriptions thereof are omitted.

  The third vibrating body 20-3, the fourth vibrating body 20-4, and the fifth vibrating body 20-5 are made of polyethylene in a thin film shape, and have the same shape as the second vibrating body 20-2. Each has a different thickness. The third vibrating body 20-3 to the fifth vibrating body 20-5 have elasticity, and are deformed when a force is applied, and vibrate by generating a restoring force by the elasticity. In the present embodiment, the material of the third vibrating body 20-3 to the fifth vibrating body 20-5 is polyethylene. However, the material is not limited to polyethylene, and polyethylene can be used if it has elasticity and vibrations are generated. Other materials such as synthetic resin, paper, metal, fiberboard, etc. may be used.

  In the sound absorbing structure 1A, as in the first embodiment, the bottom surface portion 11 is fixed to one opening portion of the side wall 12, and the first vibrating body 20-1 is fixed to the other opening portion to The first vibrating body 20-1 is parallel. Further, on the inner side of the side wall 12, the second vibrating body 20-2 is fixed to the side wall 12 in parallel with the bottom surface part 11 at a distance from the bottom surface part 11. Further, on the inner side of the side wall 12, the third vibrating body 20-3 is fixed in parallel with a distance from the second vibrating body 20-2, and the fourth vibration in parallel with a distance from the third vibrating body 20-3. The body 20-4 is fixed, and the fifth vibrating body 20-5 is fixed in parallel with a distance from the fourth vibrating body 20-4.

Thus, the inside of the housing 10 is partitioned, the first air layer 30-11 immediately behind the first vibrating body 20-1, the second air layer 30-12 immediately behind the fifth vibrating body 20-5, The third air layer 30-13 immediately behind the fourth vibrating body 20-4, the fourth air layer 30-14 immediately behind the third vibrating body 20-3, and the second air body 30-2 immediately behind the second vibrating body 20-2. Five air layers 30-15 are formed.
In the present embodiment, each air layer is hermetically sealed, but holes may be provided in the side wall 12 and the bottom surface portion 11 so that each air layer communicates with the space outside the sound absorbing structure 1A.

  Also in the sound absorbing structure 1A configured as described above, a plurality of spring mass sound absorbing mechanisms having different resonance frequencies are formed by the combination of each vibrating body and each air layer, and a peak of the sound absorption coefficient appears for each sound absorbing mechanism. Here, since each sound absorption mechanism has a different mass component or spring component, the sound frequency at which the sound absorption rate reaches a peak also varies depending on each sound absorption mechanism. That is, the sound absorbing structure 1A can also efficiently absorb sound over a wide band.

  Further, when the first vibrating body 20-1 is directed to the sound field at the boundary surfaces of various rooms and the bottom surface portion 11 is fixed in contact with the boundary surface, the plurality of vibrating bodies are used in the same manner as the sound absorbing structure 1. Multiple reflected waves that are gradually out of phase are formed. When this reflected wave reaches the sound field, the standing wave in the sound field and the natural vibration mode of the room are alleviated, and not only the sound absorption but also the noise of the room such as the vehicle compartment and the acoustic room can be reduced.

  In the present embodiment, the first vibrating body 20-1 to the fifth vibrating body 20-5 may be different materials. In addition, the first vibrating body 20-1 to the fifth vibrating body 20-5 may be made of the same material, but may have different thicknesses for each vibrating body. Further, the second vibrating body 20-2 to the fifth vibrating body 20-5 located inside the side wall 12 may have a shape (rectangular shape, polygonal shape, etc.) different from the square that is the cross-sectional shape of the side wall 12, Moreover, you may vary a shape for every 2nd vibrating body 20-2-5th vibrating body 20-5. Also in the present embodiment, a porous sound absorbing material may be disposed between the bottom surface portion 11 and the second vibrating body 20-2.

[Third Embodiment]
Next, a sound absorbing structure 1B according to a third embodiment of the present invention will be described.
7 is an external view of the sound absorbing structure 1B, FIG. 8 is an exploded perspective view of the sound absorbing structure 1B, and FIG. 9 is a cross-sectional view taken along the line BB of the sound absorbing structure 1B. In the drawings, the dimensions of the sound absorbing structure 1B are different from the actual dimensions in order to illustrate the configuration of the present embodiment in an easy-to-understand manner.

(Configuration of each part)
As shown in the drawing, the sound absorbing structure 1B includes a side wall 12, a first vibrating body 20-11, and a second vibrating body 20-12.
The side wall 12 has the same configuration as the side wall 12 of the first embodiment. The first vibrating body 20-11 and the second vibrating body 20-12 are made of a synthetic resin in a thin film shape and have a square shape. The first vibrating body 20-11 and the second vibrating body 20-12 have elasticity. The first vibrating body 20-11 and the second vibrating body 20-12 are deformed when a force is applied, and vibrate by generating a restoring force by the elasticity.

(overall structure)
In the sound absorbing structure 1B, the second vibrating body 20-12 is fixed to one opening of the side wall 12, and the first vibrating body 20-11 is fixed to the other opening, and the first vibrating body 20-11. And the second vibrating body 20-12 are parallel to each other.
In the sound absorbing structure 1B, either one of the vibrating bodies is directed to the boundary surface side of the room such as the vehicle compartment or the acoustic room, and a space is formed between the vibrating body directed to the boundary surface side and the boundary surface. (Air layer) is formed and formed.
In addition, as a method of disposing the sound absorbing structure 1B at a position away from the boundary surface, for example, one end of a columnar support member is fixed to the four corners of the sound absorbing structure 1B, and the other end of the support member is placed. There is a method of forming a space between the vibrating body and the boundary surface by fixing the surface to the boundary surface.

In the sound absorbing structure in which the sound absorbing structure 1B is arranged away from the boundary surface as shown in FIG. 9, the first vibrating body 20- is surrounded by the first vibrating body 20-11, the side wall 12, and the second vibrating body 20-12. 11, a first air layer 30-1 partitioned into a rectangular shape is located, and a second air layer 30-2 is located between the second vibrating body 20-12 and the boundary surface.
In the present embodiment, the first air layer 30-1 is hermetically sealed, but a hole may be provided in the side wall 12 so that the first air layer 30-1 communicates with the space outside the sound absorbing structure 1.

Also in the sound absorbing structure in which the sound absorbing structure 1B is separated from the boundary surface, the two vibrating bodies, the first vibrating body 20-11 and the second vibrating body 20-12, the first air layer 30-1, and the second air Since there are two air layers called the layer 30-2, a plurality of spring-mass sound absorbing mechanisms are formed as in the first embodiment.
The sound absorption rate peaks for each of the plurality of sound absorption mechanisms, and each sound absorption mechanism has a different mass component and spring component. Therefore, the frequency band of the sound at which the sound absorption rate reaches a peak also differs for each sound absorption mechanism. That is, even in the sound absorbing structure in which the sound absorbing structure 1B is arranged at a position away from the boundary surface as shown in FIG. 9, sound can be efficiently absorbed in a wide band.

The graph of (1) in FIG. 10 shows that in the sound absorbing structure 1B, the material of the first vibrating body 20-11 and the second vibrating body 20-12 is PVC (polyvinyl chloride) and the thickness is 0.5. [Mm], the vertical and horizontal dimensions of the first air layer 30-1 are 100 [mm] × 100 [mm], the thickness is 10 [mm], and the thickness of the second air layer 30-2 12 is a graph showing the measurement result of octave analysis (1/3 octave band) of the random incident sound absorption coefficient of a sound absorption structure of 20 [mm] (FIG. 11A).
For comparison, in FIG. 10, the material of the first vibrating body 20-11 is PVC, the thickness is 0.5 [mm], and the bottom surface portion 11 is changed to the side wall 12 instead of the second vibrating body 20-12. The first air layer 30-1 is fixed, the vertical and horizontal sizes are 100 [mm] × 100 [mm], the thickness of the first air layer 30-1 is 30 [mm], and the second air layer The graph (the graph of (2) of Drawing 10) of the measurement result of the random incidence sound absorption coefficient of the sound absorption structure (Figure 11 (b)) which does not have 30-2 is also shown.

As shown in FIG. 11B, when the vibration body is only the first vibration body 20-11 and the thickness of the first air layer 30-1 is increased, the sound absorption coefficient peak is around 400 [Hz]. It can be seen that appears.
On the other hand, in the case of the sound absorption structure shown in FIG. 11A, in addition to 400 [Hz] as compared with the configuration in which the thickness of the first air layer 30-1 is increased as shown in FIG. The sound absorption rate is high even in the vicinity of 315 [Hz], and it can be seen that sound absorption can be performed in a wider band than the configuration of FIG.
Further, in the sound absorbing structure according to the present embodiment shown in FIG. 10A, it is possible to absorb low-frequency sound with a sound absorbing structure thinner than the sound absorbing structure shown in FIG. In addition, it is possible to obtain an effect that sound absorption can be efficiently performed with a sound absorbing structure having a small volume.

  Even in the sound absorbing structure in which the sound absorbing structure 1B is disposed at a position away from the boundary surfaces of various rooms, sound waves other than the resonance frequency of each vibrating body are components that are transmitted through the vibrating bodies and components that are reflected by the vibrating bodies. In other words, similarly to the sound absorbing structure 1, multiple reflected waves having phases gradually shifted are formed. When this reflected wave reaches the sound field, the standing wave in the sound field and the natural vibration mode of the room are alleviated, and not only the sound absorption but also the noise of the room such as the passenger compartment or the acoustic room can be reduced.

(Modification of the third embodiment)
In the sound absorbing structure 1B described above, a porous sound absorbing material may be disposed between the first vibrating body 20-11 and the second vibrating body 20-12.

In the sound absorbing structure 1B described above, the first vibrating body 20-11 and the second vibrating body 20-12 are parallel to each other. However, as shown in FIG. 20-11 may be non-parallel to the second vibrating body 20-12 at a predetermined angle.
In addition, when arrange | positioning the sound absorption structure shown to Fig.12 (a), as shown to Fig.12 (a), you may arrange | position so that the 2nd vibrating body 20-12 may become parallel to a boundary surface, As shown in FIG. 12B, the first vibrating body 20-11 may be arranged so as to be parallel to the boundary surface.
Moreover, as shown in FIG.12 (c), you may arrange | position so that both the 1st vibrating body 20-11 and the 2nd vibrating body 20-12 may not become parallel to a boundary surface.
From the standpoint that the vibrating body is not parallel to the boundary surface, the first sound-absorbing structure in which the first vibrating body 20-11 and the second vibrating body 20-12 are parallel as shown in FIG. You may arrange | position so that both the vibrating body 20-11 and the 2nd vibrating body 20-12 may not become parallel to a boundary surface.

Further, in the above-described embodiment, the second vibrating body 20-12 is plate-like and flat, but when viewed in cross section like the second vibrating body 20-13 shown in FIG. It may be a undulating shape. The undulations of the second vibrating body 20-13 may be periodically undulations such as sine waves and square waves, or may be irregular undulations.
When the sound absorbing structure shown in FIG. 13A is disposed, the first vibrating body 20-11 may be parallel to the boundary surface, and the first vibrating body 20-11 is the boundary surface. You may make it not parallel to.
When the sound absorbing structure shown in FIG. 13A is used, the first vibrating body 20-11 is opposed to the boundary surface in parallel, and the second vibrating body 20-13 is arranged facing the sound field. In addition, when the first vibrating body 20-11 is opposed to the boundary surface, the first vibrating body 20-11 is opposed so as not to be parallel to the boundary surface, and the second vibrating body 20- You may make it arrange | position 13 toward a sound field.

In the above-described embodiment, the sound absorbing structure 1B is disposed so as to face the flat boundary surface. However, as shown in FIG. You may make it arrange | position the sound-absorbing structure 1B facing a boundary surface.
Also in the sound absorbing structure 1 </ b> B, a plurality of vibrating bodies may be fixed inside the side wall 12, and a plurality of air layers may be provided inside the side wall 12.

[Modification]
As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It can implement with another various form. For example, the present invention may be implemented by modifying the above-described embodiment as follows.

  In the present invention, the vibrating body may be either plate-shaped or film-shaped (film-shaped or sheet-shaped) as long as it has elasticity and vibrates. The plate shape means that the thickness is relatively thin with respect to a rectangular parallelepiped (solid) and has a two-dimensional extension, and the film shape (film shape, sheet shape) is more than the plate shape. It means that the thickness is relatively thin and a restoring force is generated by tension.

In the present invention, the material of the vibrator is chlorinated polyethylene, polyvinyl chloride, polyethylene terephthalate, polyester, synthetic rubber (isoprene rubber, nitrile rubber, fluororubber, butadiene styrene copolymer, copolymer polymer, etc.), polyamide It may be mainly composed of an organic polymer, or may be composed mainly of an inorganic polymer such as silicone rubber.
In addition, these materials may contain organic small molecules (plasticizers, crosslinking agents, crosslinking accelerators, antioxidants) and inorganic fillers.

  The material of the housing 10 may be other materials such as thermoplastic plastics such as polypropylene and polyamide, thermosetting plastics such as epoxy resin, and fiber reinforced plastics instead of ABS.

  The sound absorbing structure according to the present invention described above has a square shape when viewed from above, but the shape when viewed from above is rectangular, trapezoidal, polygonal, circular, elliptical, or the like. You may form a vibrating body and a housing | casing so that it may become a shape.

In addition, when arrange | positioning the sound-absorbing structure which concerns on embodiment mentioned above or a modification, you may arrange | position the sound-absorbing body group which combined two or more sound-absorbing structures with the same magnitude | size.
Further, when a plurality of sound absorbing structures are combined, the material, thickness, density, Young's modulus, and loss tangent (tan δ) of the vibrator may be different for each sound absorbing structure to be combined.
When a plurality of sound absorbing structures are combined, the thickness of the air layer may be varied for each sound absorbing structure. Further, the size of the air layer may be varied, and both the thickness and the size of the air layer may be varied.

  Further, in the sound absorbing structure according to the present invention, the inside of the housing 10 is divided into a lattice shape by the partition member 13 as shown in FIG. 14 so that a plurality of air layers are formed inside the side wall 12. Also good.

  In the above-described embodiment, the vibrating body is fixedly supported by being fixed to the side wall 12. Although the displacement (movement) and rotation are restricted at the fixing portion, the vibrating body is displaced with respect to the side wall 12. May be a simple support state in which rotation is allowed and rotation is allowed. Further, other support states such as a support state in which displacement is allowed and a free support may be used.

  The above-described sound absorbing structure according to the present invention may be disposed in a place where the sound having the peak frequency of the sound absorption coefficient of the sound absorbing structure is generated as noise to reduce noise. As described above, according to the noise reduction method in which the sound absorbing structure is arranged at a place where noise is generated to reduce noise, the vibration body vibrates, noise energy is consumed, and noise is reduced. Note that the noise generation location includes, for example, various machines operating in factories, construction sites, etc., inside various transportation equipment such as vehicles and airplanes.

1 is an external view of a sound absorbing structure 1 according to an embodiment of the present invention. 1 is an exploded perspective view of a sound absorbing structure 1. FIG. 1 is a cross-sectional view of a sound absorbing structure 1. FIG. 4 is a graph showing a measurement result of a sound absorption rate of the sound absorption structure 1. It is sectional drawing of the sound absorption structure used for the measurement of a sound absorption coefficient. It is sectional drawing of the sound absorption structure 1A which concerns on 2nd Embodiment of this invention. It is an external view of the sound absorption structure 1B which concerns on 3rd Embodiment of this invention. It is a disassembled perspective view of the sound absorption structure 1B. It is sectional drawing of the sound absorption structure 1B. It is the graph which showed the measurement result of the sound absorption rate of the sound absorption structure concerning a 3rd embodiment. It is sectional drawing of the sound absorption structure used for the measurement of a sound absorption coefficient. It is sectional drawing of the sound absorption structure which concerns on the modification of this invention. It is sectional drawing of the sound absorption structure which concerns on the modification of this invention. It is an exploded view of the sound absorption structure concerning a modification of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A, 1B ... Sound absorption structure, 10 ... Case, 11 ... Bottom surface part, 12 ... Side wall, 13 ... Partition member, 20-1 to 20-5, 20-11 20-13 ... Vibrating body, 30-1, 30-2, 30-11-30-15 ... Air layer.

Claims (5)

A plurality of plate-like or film-like vibrators;
A side wall in the shape of a tube with a hollow portion, and
The vibrating body is fixed to the side wall so as to close the hollow portion,
The plurality of vibrators are arranged non-parallel, and the surface faces the surface of another vibrator at a distance,
A sound absorbing structure in which the vibrating body and the air layer are alternately stacked.   The sound absorbing structure according to claim 1, wherein the plurality of vibrators have different thicknesses.   The sound absorbing structure according to claim 1, wherein the number of the vibrating bodies is three or more.   The sound absorbing structure according to claim 1, wherein the air layer has a porous sound absorbing material.   The non-vibrating body having higher rigidity than the vibrating body faces one of two outermost vibrating bodies among the plurality of vibrating bodies alternately overlapping with the air layer. Item 2. The sound absorbing structure according to Item 1.

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