A composite porous sound absorbing structure with embedded opposed membrane cavity resonators

Abstract

The present invention relates to the field of noise control, and more specifically to a composite porous sound-absorbing structure with embedded opposed membrane cavity resonators, including a porous material and a membrane cavity resonator. The membrane cavity resonator includes a cavity with a single opening and a thin film for closing the cavity. The membrane cavity resonator is provided with two mirror-symmetrical portions and embedded in the porous material, with the cavity opening at the top facing upward, thereby solving the problem of poor sound absorption performance of thin porous materials at medium and low frequencies and providing a new solution for improving the noise reduction performance of porous materials.

Description

Technical Field

[0001] The invention relates to the field of noise control, and more specifically to a composite porous sound absorbing structure with an embedded opposed membrane cavity resonator. Background Art

[0002] Noise pollution is a major problem that damages human physical and mental health in modern society. Noise control, especially the elimination of medium and low frequency noise, is a research hotspot in the fields of aerospace, transportation, and building environment.

[0003] Since the introduction of acoustic metamaterials, they have provided many new ideas for the development of traditional noise reduction materials and structures. The characteristics of subwavelength resonant structure design and customization of acoustic performance make them have incomparable advantages in low-frequency broadband noise, and have attracted widespread attention from academia and industry. The research on the design of porous materials with excellent mid- and high-frequency performance combined with various subwavelength structures with outstanding low-frequency performance to improve the mid- and low-frequency sound absorption performance of porous materials has also received widespread attention. The design method of combining the strengths of others to overcome the weaknesses is the mainstream development direction of the next generation of porous noise reduction materials with great potential.

[0004] In recent years, embedding single or multiple low-frequency resonators and non-local resonance units in the porous material domain has effectively improved the mid- and low-frequency sound absorption performance of porous materials. However, the absorption peaks of most structures at mid- and low frequencies are relatively discrete, and the limited number of absorption peaks makes it difficult to form a continuous high sound absorption spectrum in the frequency band of interest.

[0005] Generally speaking, traditional porous materials can effectively eliminate mid- and high-frequency noises. However, due to the limitation of the dissipation principle, porous materials need to be thicker to effectively eliminate mid- and low-frequency noises. However, excessive thickness limits their application in many scenarios. Therefore, how to effectively improve the absorption capacity of porous materials for mid- and low-frequency noises without increasing their thickness has always been a difficulty in this field. Summary of the invention

[0006] The invention provides a composite porous sound absorbing structure with embedded opposed membrane cavity resonators, aiming to solve the problem of poor low-frequency sound absorption performance of porous materials.

[0007] The above purpose is achieved through the following technical solutions:

[0008] A composite porous sound absorbing structure with embedded opposed membrane cavity resonators comprises a porous material and a membrane cavity resonator. The membrane cavity resonator comprises a cavity with a single opening and a film for closing the cavity. Two membrane cavity resonators are mirror-symmetrically arranged and embedded in the porous material, with the cavity opening located on the upper side facing upward.

[0009] Furthermore, the film is made of an elastomeric polymer material or metal, and the thickness of the film is between 0.1 mm and 1 mm.

[0010] Furthermore, a plate is provided between the film and the cavity to form an air layer of 0.1 mm to 2 mm.

[0011] Furthermore, the lower end surface of the membrane cavity resonator film located below is higher than the lower end surface of the porous material to form an air layer with a height of millimeters between the film located below and the lower end surface of the porous material. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a cross-sectional view of the overall structure of a composite porous sound absorbing structure with an embedded opposed membrane cavity resonator according to the present invention;

[0013] Figure 2 is an exploded view of the overall structure;

[0014] Figure 3 The figure is a curve showing that the sound absorption structure can produce an average sound absorption coefficient of 90% in the medium and low frequency bands, and a comparison chart with the sound absorption of porous materials of the same thickness. DETAILED DESCRIPTION

[0015] like Figures 1 to 2 As shown, a composite porous sound absorbing structure with an embedded opposed membrane cavity resonator includes a porous material 5 and two membrane cavity resonators embedded in the porous material, the two membrane cavity resonators are arranged in mirror symmetry in position, one of the membrane cavity resonators is located at the top, and the other is located at the bottom; the membrane cavity resonator includes a film, an annular gasket, a plate with an opening and a cavity, which are further described as follows for the convenience of description and distinction:

[0016] Among them, the membrane cavity resonator located at the top, that is, the upper membrane cavity resonator includes an upper film 1, an upper gasket 2, an upper perforated plate 3 and a cavity 4 with an opening facing upward; specifically, the upper film 1 is bonded to the edge of the upper perforated plate 3 through the gasket 2, and a thin air layer is formed between the upper film 1, the upper gasket 2 and the upper perforated plate 3. The upper film 1 and the air layer provide acoustic mass reactance and acoustic resistance for the system, while the cavity 4 with an opening facing upward provides capacitive reactance for the system. The size of the perforations in the upper perforated plate 3 and the height of the upper gasket 2 mainly adjust the acoustic reactance and acoustic resistance of the air layer, thereby forming a complete set of adjustable acoustic resonators;

[0017] The membrane cavity resonator located at the bottom, i.e., the lower membrane cavity resonator, includes a cavity 6 with an opening facing downward, a lower perforated plate 7, a lower gasket 8 and a lower film 9; wherein, similarly, the lower film 9 is bonded to the edge of the lower perforated plate 7 through the lower gasket 8, and a thin air layer is formed between the lower film 9, the lower gasket 8 and the lower perforated plate 7, and the lower film 9 and the air layer provide acoustic mass reactance and acoustic resistance for the system, while the cavity 6 with an opening facing downward provides capacitive reactance for the system, and the perforation size of the lower perforated plate 7 and the height of the lower gasket 8 mainly adjust the acoustic reactance and acoustic resistance of the air layer, thereby also forming a complete set of adjustable acoustic resonators; the cavity 4 with an opening facing upward and the cavity 6 with an opening facing downward are arranged back to back and are both embedded in the porous material 5;

[0018] The thin air layer has a height of 0.1 mm to 2 mm;

[0019] Among them, the sizes and specific structures of the upper membrane cavity resonator and the lower membrane cavity resonator can be different. For example, the overall sizes of the cavity 4 with the opening facing upward and the cavity 6 with the opening facing downward are different, and their internal cavity structures are also different; after the openings are set in the plate, the specific structures of the upper perforated plate 3 and the lower perforated plate 7 are different, such as the number of openings, the size of the openings and the specific shape of the openings are different.

[0020] This composite porous structure can solve the problem of poor low-frequency sound absorption of pure porous materials and provide a new solution for noise reduction applications of thin and light porous materials.

[0021] Among them, the upper film cavity resonator mainly uses resonance to absorb low-frequency sound peaks; the lower film 9 in the lower film cavity resonator is higher than the bottom surface of the porous material 5 to leave a certain height of air layer to ensure that the lower film 9 can vibrate freely. The existence of the lower film cavity resonator is mainly to excite multiple energy consumption modes of the porous material to form multiple medium-frequency absorption peaks.

[0022] Furthermore, the upper film 1 in the upper film cavity resonator can be flush with, higher than, or lower than the upper surface of the porous material.

[0023] Furthermore, the material of the upper film 1 and the lower film 9 can be one of rubber, latex, plastic, and metal, with a thickness between 0.1-1 mm, and no prestress is required for the upper film 1 and the lower film 9. The upper film 1 and the lower film 9 of different thicknesses can provide different mass resistances for the resonator, thereby adjusting the sound absorption frequency.

[0024] Furthermore, the membrane cavity resonator can be embedded in the center or eccentric position of the porous material.

[0025] Furthermore, the upper perforated plate 3 and the lower perforated plate 7 have a single or multiple openings, which may be one or more combinations of circular, square, annular, straight slot and slit shapes. The openings may be millimeter-sized or relatively larger than the millimeter-sized openings. Adjusting the size of the perforations may adjust the acoustic reactance and acoustic resistance of the system, thereby adjusting the position and height of the sound absorption peak.

[0026] Furthermore, the interior of the cavity 4 with the opening facing upward and the cavity 6 with the opening facing downward is a pure cavity and a space folding type. The upper and lower membrane cavity resonators can adjust the height according to the required anxiety frequency band to obtain a continuous sound absorption spectrum with a minimum of more than 0.8 in the medium and low frequency bands. The sound absorption curve of the porous composite material with a total thickness of 60 mm is compared with the sound absorption curve of the pure porous material with the same thickness. Figure 3 shown.

[0027] The overall structure of the present application can achieve an average sound absorption of 90% in the medium and low frequencies with a sub-wavelength thickness, solving the problem of poor sound absorption performance of thin porous materials in the medium and low frequencies, providing a new solution for improving the noise reduction performance of porous materials, and achieving continuous high sound absorption in the medium and low frequency bands.

Claims

1. A composite porous sound-absorbing structure with embedded opposing membrane cavity resonators, comprising a porous material and a membrane cavity resonator, wherein the membrane cavity resonator comprises a cavity with a single opening and a thin film for closing the cavity, and wherein two membrane cavity resonators are mirror-symmetrically arranged and embedded in the porous material, with the cavity opening located on the upper side facing upward.

2. The sound absorbing structure according to claim 1, wherein the membrane cavity resonator is located at a central position or an eccentric position of the porous material.

3. According to the sound absorbing structure of claim 1, the upper end surface of the film of the membrane cavity resonator located above is flush with, lower than or higher than the upper end surface of the porous material. 4 . The sound absorbing structure according to claim 1 , wherein the film is made of an elastomeric polymer material or a metal, and the thickness of the film is between 0.1 mm and 1 mm.

5. According to the sound absorbing structure of claim 1, both cavities are pure cavities, or both cavities are space folded cavities.

6. The sound absorbing structure according to any one of claims 1 to 5, wherein a plate is provided between the film and the cavity to form an air layer of 0.1 mm to 2 mm.

7. The sound absorbing structure according to claim 6, wherein the film is fixed to the plate through an annular gasket. The sound absorbing structure according to claim 7 , wherein the plate is provided with an opening.

9. The sound absorbing structure according to claim 8, wherein the shape of the opening on the plate is one or more of a circular shape, a square shape, a ring shape, a straight slot shape and a slit shape.

10. According to the sound absorbing structure described in claim 1, 2, 3, 4, 5, 7, 8 or 9, the lower end surface of the membrane cavity resonator film located below is higher than the lower end surface of the porous material to form an air layer with a height of millimeters between the film located below and the lower end surface of the porous material.

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