JP2004170665A - Sound absorption and insulation structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sound absorption and insulation structure for realizing not only noise of a specified frequency band, but also efficient absorption to the noise of a wide frequency band. <P>SOLUTION: The sound absorption and insulation structure 10 includes a plurality of sound absorption cells 71 and a substantially sheet-like sound absorption material 60 covering openings of the plurality of the sound absorption cells 71. The plurality of the sound absorption cells 71 are mutually adjacently arranged, have the openings in only one direction (Z direction), and depths H thereof from an opening face to a bottom face are respectively different. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a sound absorbing and insulating structure for absorbing and blocking harsh noise.
[0002]
[Prior art]
2. Description of the Related Art As a conventional sound absorbing device, there is known a sound absorbing device in which a box portion is formed inside a sound absorbing device main body and a communication pipe for communicating the box portion with an engine room is provided (for example, see Patent Document 1). This conventional sound absorbing device constitutes a resonance type sound absorbing device, and it is possible to enhance the sound absorbing performance against low frequency noise in the engine room by opening the internal space of the box portion on the engine room side through a communication pipe. And
[0003]
Further, as another conventional sound absorbing device, a partition plate that includes a substantially flat substrate and a sound absorbing material facing the substrate, and divides an air layer between the substrate and the sound absorbing material into a plurality of lattice-shaped cells. A sound absorbing device further provided is known (for example, see Patent Document 2). In this conventional sound absorbing device, the thickness of the air layer behind the sound absorbing material (that is, the depth of each cell) is set to １ ／ times the wavelength of the sound wave to be absorbed, so that the energy of the sound wave is efficiently reduced. It is aiming for a great attenuation. According to this conventional sound absorbing device, the sound absorbing ratio of a specific frequency component is improved, and the sound absorbing performance is improved and the weight is reduced.
[0004]
[Patent Document 1]
Japanese Utility Model Publication No. 3-64855 [Patent Document 2]
JP-A-11-161282 (6 tribute, FIG. 16)
[0005]
[Problems to be solved by the invention]
By the way, noises in a wide frequency range mainly including engine combustion noise (about 1 kHz to 3 kHz) exist in an engine room or a vehicle interior of a vehicle. For this reason, in a vehicle engine room or the like, it is necessary to effectively absorb noise in a relatively wide frequency range. However, in the above-described conventional sound absorbing device, since the sound absorbing effect is concentrated in a specific frequency band, the sensual sound absorbing effect perceived by a human can be enhanced, but the sound absorbing effect is good in a space where noise in a relatively wide frequency range exists. There is a problem that a great sound absorbing effect cannot be obtained.
[0006]
Therefore, an object of the present invention is to provide a sound absorbing and insulating structure that can realize efficient sound absorption not only for noise in a specific frequency band but also for noise around the specific frequency band.
[0007]
[Means for Solving the Problems]
The above object is, as described in claim 1, a plurality of sound absorbing cells arranged adjacent to each other, having an opening only in one direction, and having different depths from the opening surface to the bottom surface,
A sound absorbing material that covers the openings of the plurality of sound absorbing cells.
[0008]
In the present invention, the sound absorbing and insulating structure includes a plurality of sound absorbing cells arranged adjacent to each other and a sound absorbing material. The plurality of sound absorbing cells have openings only on the side where the sound absorbing material is provided, and have respective bottom surfaces at positions separated by different distances from the respective openings. When a sound wave is input to the plurality of sound absorbing cells, a standing wave is formed in each sound absorbing cell by combining the incident wave and the reflected wave reflected on the bottom surface. According to the present invention, since the plurality of sound absorbing cells have their bottom surfaces at different distances from the respective openings, the phases of the standing waves at the opening positions are different from each other among the sound absorbing cells. As a result, a wavefront spreading in the opening surface of the sound absorbing cell is generated, and efficient sound absorption by the sound absorbing material provided in the opening surface is realized.
[0009]
Further, according to the present invention, since the plurality of sound absorbing cells have respective bottom surfaces at positions different from the respective openings by different distances, when a sound wave of a certain frequency is input, the sound absorbing material is placed in a certain sound absorbing cell at the position of the sound absorbing material. When a sound wave having a frequency different from the above frequency is input, a standing wave that forms an antinode at the position of the sound absorbing material is formed in a sound absorbing cell different from the sound absorbing cell. It is possible to efficiently absorb sound waves in a wide frequency range.
[0010]
In addition, the sound absorbing and insulating structure according to the present invention preferably further includes a rib erected on a bottom surface of the sound absorbing cell. Thus, the rigidity of the bottom surface of the sound absorbing cell is increased, and transmitted sound can be reduced.
[0011]
In the sound absorbing and insulating structure according to the present invention, the plurality of different depths of the sound absorbing cell are preferably set within a range in which a value of 1/4 times the wavelength of sound in a frequency band to be absorbed can be taken. Accordingly, the sound wave in the predetermined frequency band passes through the sound absorbing material at a position having the highest particle velocity (that is, a position of the antinode of the standing wave) in any of the sound absorbing cells. A good sound absorbing effect can be obtained over a frequency band.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a perspective view partially showing a sound absorbing and insulating structure according to the present invention, and FIG. 2 is a sectional view of the sound absorbing and insulating structure according to the present invention. The sound absorbing device 10 having the sound absorbing and insulating structure according to the present invention includes a sound absorbing material 60 and a cell structure 50 as described in detail below.
[0013]
The cell structure 50 has a plurality of sound absorbing cells 71 having openings on the sound absorbing material 60 side (Z direction side in FIG. 1). Each sound absorbing cell 71 is closed except for the opening on the sound absorbing material 60 side, and has an opening surface in substantially the same plane. As shown in FIGS. 1 and 2, each sound absorbing cell 71 has a different depth H (depth in the Z direction in FIG. 1) with respect to each adjacent sound absorbing cell 71. The cell structure 50 may be formed of an aluminum plate, a steel plate, or the like, or may be integrally formed of a hard resin such as a polypropylene resin.
[0014]
The sound absorbing material 60 has a substantially flat sheet shape, is provided in the opening surface of the cell structure 50 sound absorbing cell 71, and covers the opening of each sound absorbing cell 71. The sound absorbing material 60 is made of a material having sound absorbing performance, for example, inorganic fiber such as glass wool or rock wool, metal fiber material such as aluminum fiber, synthetic resin foam such as polystyrene resin or polyethylene resin, urethane or rubber. It may be formed from a system soft material, a porous material, or the like.
[0015]
Next, the sound absorbing principle of the sound absorbing device 10 according to the present invention will be described with reference to FIG.
[0016]
Referring to FIG. 3, when a sound wave having a wavelength λ enters the sound absorbing device 10, a standing wave is formed in the sound absorbing cell 71 by combining the incident wave and the reflected wave. This standing wave has an antinode at a position away from the bottom surface 72 of the sound absorbing cell 71 by an odd multiple of 波長 of the wavelength λ, and the particle velocity of the sound wave becomes maximum at the antinode. Therefore, if the sound absorbing material 60 is provided at the position where the particle velocity is maximum, and the sound wave passes through the sound absorbing material 60 at the position having the highest particle velocity, the sound wave can be attenuated most efficiently.
[0017]
For this purpose, the depth H of the sound absorbing cell 71 according to the present invention is set to 1/4 (or an odd multiple thereof) the wavelength λ of the sound wave to be absorbed. Further, the opening width A of the sound absorbing cell 71 is set smaller than the wavelength λ of the sound wave in the frequency band to be absorbed in order to realize efficient input of the sound wave to the sound absorbing cell 71.
[0018]
By the way, in the sound absorbing device 10 according to the present invention, as described above, each sound absorbing cell 71 has a different depth H with respect to each adjacent sound absorbing cell 71. Therefore, when a sound wave of wavelength λ enters the sound absorbing cell 71a whose depth H is set to λ / 4, a standing wave having an antinode at the position of the sound absorbing material 60 is formed in the sound absorbing cell 71a as described above. On the other hand, a standing wave having an antinode below the position of the sound absorbing material 60 is formed in a sound absorbing cell 71b having a different depth H (in this example, a depth H> λ / 4) adjacent to the sound absorbing cell 71a. Will be. In such a case, considering the above-described sound absorbing principle, it seems that the sound wave incident on the sound absorbing cell 71a is efficiently attenuated, whereas the sound wave incident on the sound absorbing cell 71b is not efficiently attenuated.
[0019]
However, in the sound absorbing device 10 according to the present invention, as described above, since the opening surfaces of the respective sound absorbing cells 71 are spread in substantially the same plane, the interaction of air particles is likely to be caused near the opening surfaces, and as a result, Sound waves can be efficiently attenuated. More specifically, since the particle velocity of each standing wave formed by the adjacent sound absorbing cells 71a and 71b differs at the position of the sound absorbing material 60 as described above, the pressure balance (the density of air) at the position of the sound absorbing material 60. Collapses, causing a phenomenon that air particles are pushed out or pulled back in the lateral direction. As a result, an increase in the particle velocity on the inner surface of the sound absorbing material 60 (in the opening surface of the sound absorbing cell 71) is promoted, and the sound absorbing material 60 can achieve effective sound absorption.
[0020]
As described above, according to the sound absorbing device 10 of the present invention, by setting the depths H of the plurality of sound absorbing cells 71 having the opening surfaces in substantially the same plane to different values, the air particles in the vicinity of the sound absorbing material 60 can be reduced. Effective sound absorption utilizing the interaction can be realized.
[0021]
Further, since the sound absorbing device 10 according to the present invention has the sound absorbing cells 71 having different depths H as described above, it is possible to effectively absorb noise in a wide frequency range by cooperation of the sound absorbing cells 71. it can. That is, the depth H of each sound absorbing cell 71 is a value of １ ／ wavelength of the sound wave in the predetermined frequency range in order to realize efficient sound absorption over a predetermined frequency range (for example, 1 kHz to 3 kHz). It is set within the range (for example, about 28 mm to 85 mm). Therefore, according to the sound absorbing device 10 of the present invention, it is possible to obtain a good sound absorbing effect even in an engine room or a vehicle interior where noises in a wide frequency range mainly including engine combustion noise (about 1 kHz to 3 kHz) are present. Is possible.
[0022]
Further, since the sound absorbing device 10 according to the present invention has the sound absorbing cells 71 having different depths H as described above, the bottom 50b of the cell structure 50 has high rigidity as a whole, and the cell structure 50 has a high rigidity. It is possible to effectively lose the energy of sound when transmitting through the bottom 50b. Therefore, in the sound absorbing device 10 according to the present invention, since the cell structure 50 also has high sound insulation performance against sound from behind (the bottom 50b side), the quietness of the space where the sound absorbing cell 71 is opened can be further enhanced. Can be.
[0023]
In order to further enhance the sound insulation performance, as shown in FIG. 4, a rib 73 may be provided upright on the bottom surface 72 of each sound absorbing cell 71 constituting the bottom 50b of the cell structure 50. That is, by providing the rib 73 on the bottom surface 72 of the sound absorbing cell 71, the rigidity of the bottom portion 50b of the cell structure 50 is further increased, and the sound insulating performance of the sound absorbing device 10 against sound from behind can be further improved.
[0024]
Next, the installation method of the sound absorbing device 10 according to the present invention and the related sound insulation performance will be described with reference to FIGS.
[0025]
As shown in FIG. 5, the sound absorbing device 10 may be fixed at a predetermined position by a body panel (for example, a floor panel or a roof panel) or a bracket 12 fixed to an engine support member. In this case, the sound absorbing device 10 is supported by the bracket 12 on the side 50a of the cell structure 50 so that the bottom 50b of the cell structure 50 is separated from the body panel or the like. This can prevent direct transmission of vibration of the body panel or the like to the bottom 50b of the cell structure 50.
[0026]
Alternatively, as shown in FIG. 6, the sound absorbing device 10 can be fixed at a predetermined position by fastening the bottom surface 72 of the sound absorbing cell 71 having the largest depth H to a body panel or the like with a screw or the like, or by fixing with an adhesive or the like. It may be installed. In this case, by setting the sound absorbing cell 71 defining the outer periphery of the cell structure 50 to the largest depth H, a stable installation state of the sound absorbing device 10 is realized, and the sound absorbing device 10 is provided behind the cell structure 50. It is also possible to define a new sound absorbing cell 74 and realize sound absorbing and insulating using the sound absorbing cell 74. For example, as shown in FIG. 6, by interposing a low spring material 75 having a sound absorbing property between the bottom 50b of the cell structure 50 and the body panel, the sound absorbing device 10 using the low spring material 75 and the sound absorbing material 60 is provided. It is possible to realize sound absorption on both sides (both sides in the Z direction in FIG. 1) and to improve the sound insulation at the bottom 50b of the cell structure 50.
[0027]
Note that the sound absorbing device 10 may be installed at a predetermined position such that sound waves from the sound source 14 (for example, an engine) are vertically incident on the openings of the sound absorbing cells 71 as shown in FIG. In this case, the above-described standing wave is easily formed in each sound absorbing cell 71, and efficient sound absorption is realized by the above sound absorbing principle. Alternatively, the sound absorbing device 10 may be installed at a predetermined position such that sound waves from the sound source 14 obliquely enter the openings of the sound absorbing cells 71 as shown in FIG. In such a case, when the sound wave from the sound source 14 passes through the surface of each sound absorbing cell 71, the action on the adjacent sound absorbing cell 71 is performed with a phase difference, so that the velocity of the particles passing through the sound absorbing material 60 increases. Further, when passing through the end 76 of each sound absorbing cell 71, a sound wave traveling in the plane of the sound absorbing material 60 is generated, and the sound absorbing material 60 realizes effective sound absorption.
[0028]
Although the preferred embodiment of the present invention has been described in detail, the present invention is not limited to the above-described embodiment, and various modifications and substitutions can be made to the above-described embodiment without departing from the scope of the present invention. Can be added.
[0029]
For example, one sound absorbing cell 71 does not necessarily have to have a different depth for all of up to six sound absorbing cells 71 adjacent to the one sound absorbing cell 71, and is the same as a part of the adjacent sound absorbing cell 71. It may have a depth. The distribution of the same type of sound absorbing cells 71 having the same depth does not necessarily have to be regular, and may have irregularities corresponding to the surrounding acoustic characteristics and the like. Also, the opening width A of the sound absorbing cells 71 (see FIG. 3) does not necessarily have to be the same for each sound absorbing cell 71, and has a different value according to the difference in the wavelength of the sound wave to be absorbed as described above. Good.
[0030]
【The invention's effect】
Since the present invention is as described above, the following effects can be obtained. That is, according to the present invention, sound waves in a wide frequency range can be efficiently absorbed by arranging a plurality of sound absorbing cells having different depths. Further, by providing a rib on the bottom surface of the sound absorbing cell, transmitted sound can be reduced.
[Brief description of the drawings]
FIG. 1 is a perspective view partially showing a sound absorbing and insulating structure according to the present invention.
FIG. 2 is a cross-sectional view of the sound absorbing and insulating structure according to the present invention.
FIG. 3 is an explanatory diagram of a sound absorbing principle of the sound absorbing and insulating structure according to the present invention.
FIG. 4 is a perspective view showing ribs provided on the bottom surface of the sound absorbing cell.
FIG. 5 is an explanatory diagram of a method for installing a sound absorbing device according to the present invention.
FIG. 6 is an explanatory view of a method for installing a sound absorbing device according to the present invention.
[Explanation of symbols]
10 sound absorbing device 10
12 Bracket 50 Cell structure 50a Side 50b Bottom 60 Sound absorbing material 71 Sound absorbing cell 72 Bottom 73 Rib 74 Sound absorbing cell 75 Low spring material A Opening width H of sound absorbing cell H Depth of sound absorbing cell

Claims (3)

A plurality of sound absorbing cells arranged adjacent to each other, having an opening only in one direction, and having different depths from the opening surface to the bottom surface,
A sound absorbing material covering openings of the plurality of sound absorbing cells. The sound absorbing and insulating structure according to claim 1, further comprising a rib provided on a bottom surface of the sound absorbing cell. The sound absorbing and insulating structure according to claim 1, wherein the plurality of different depths of the sound absorbing cell belong to a range in which a value of 倍 times the wavelength of sound in a frequency band to be absorbed can be taken.

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