Perforated foamed aluminum composite acoustic panel and preparation method thereof

Abstract

The invention provides a perforated foamed aluminum composite acoustic panel and a preparation method thereof.The perforated foamed aluminum composite acoustic panel comprises a foamed aluminum plate, non-woven fabric and a perforated aluminum plate which are arranged in a stacked mode, the foamed aluminum plate is made of closed-cell foamed aluminum, and a plurality of first through holes penetrating in the thickness direction are formed in the foamed aluminum plate; a plurality of first through holes are formed in the foamed aluminum plate and evenly distributed in the foamed aluminum plate, a plurality of second through holes are formed in the perforated aluminum plate and evenly distributed in the perforated aluminum plate, the non-woven fabric is coated with adhesive, and the foamed aluminum plate and the perforated aluminum plate are bonded and combined through the non-woven fabric. The closed-cell foamed aluminum plate is perforated, part of holes of the material are communicated, a viscous effect is generated, the sound absorption performance of the material can be integrally improved, the perforated aluminum plate and the foamed aluminum plate are compounded, and the difference value of sound absorption coefficients of different frequency bands can be reduced through superposition of multi-medium sound absorption materials, so that the sound absorption performance of the material is improved. A good sound absorption effect is achieved in a wider frequency range, and the noise reduction coefficient is improved.

Description

Technical Field

[0001] The invention relates to the technical field of sound absorbing materials, and in particular to a perforated foam aluminum composite sound absorbing board and a preparation method thereof. Background Art

[0002] ‌Foamed aluminum is an excellent sound-absorbing material with significant mid- and low-frequency sound-absorbing capabilities. ‌Compared with traditional sound-absorbing materials, foamed aluminum meets environmental protection requirements and has the advantages of being lightweight and durable. It has good application prospects in the fields of construction, transportation, etc.

[0003] However, research has found that the sound absorption effect of foamed aluminum on sounds of different frequencies varies greatly. The sound absorption peak generally occurs at 750~1000Hz, and the peak sound absorption coefficient can reach about 0.8. In the frequency range of 250~500Hz and 1250~2500Hz, the sound absorption coefficient will be significantly reduced, and the overall noise reduction coefficient is about 0.5. Existing technology points out that the sound absorption performance can be improved by adjusting the porosity of foamed aluminum. Although this method can improve the noise reduction coefficient of the material, there are still large differences in the sound absorption capacity of each frequency band, and it is impossible to take into account both low-frequency and high-frequency sound absorption effects. Summary of the invention

[0004] In view of the deficiencies of the prior art, the technical problem to be solved by the present invention is how to improve the low-frequency and high-frequency sound absorption effects of foam aluminum materials, reduce the difference in sound absorption coefficients of various frequency bands, and improve the noise reduction coefficient.

[0005] In order to solve the above problems, the present invention provides a perforated foam aluminum composite sound-absorbing panel, comprising a foam aluminum plate, a non-woven fabric and a perforated aluminum plate arranged in a stacked manner, the foam aluminum plate is made of closed-cell foam aluminum, the foam aluminum plate is provided with a plurality of first through holes penetrating along the thickness direction, each of the first through holes is evenly distributed on the foam aluminum plate, the perforated aluminum plate is provided with a plurality of second through holes, each of the second through holes is evenly distributed on the perforated aluminum plate, the non-woven fabric is coated with an adhesive, and the foam aluminum plate and the perforated aluminum plate are bonded together by the non-woven fabric.

[0006] The present invention punches holes in a closed-cell foam aluminum plate to connect some of the holes in the material, thereby generating a viscous effect, which can improve the overall sound absorption performance of the material. The perforated aluminum plate is compounded with the foam aluminum plate, and the difference in sound absorption coefficients of different frequency bands can be reduced by superimposing multi-medium sound absorption materials, thereby achieving a good sound absorption effect in a wider frequency range and improving the noise reduction coefficient. The foam aluminum plate and the perforated aluminum plate are bonded together by non-woven fabric to prevent adhesive from entering the holes of the foam aluminum plate and the perforated aluminum plate, thereby ensuring the sound absorption effect.

[0007] Furthermore, the first through hole and the second through hole are arranged in a staggered manner, that is, the positions of the first through hole and the second through hole are completely staggered and will not overlap, so as to ensure that the sound waves are reflected and absorbed multiple times in the composite sound-absorbing board, increase the transmission path of the sound waves, and thus enhance the sound absorption effect.

[0008] Furthermore, the opening rate of the foam aluminum plate is 1% to 10%. As the opening rate increases, the sound absorption peak shifts to high frequency, and the difference in the sound absorption coefficient of the frequency band decreases, but the increase in the opening rate will reduce the peak value of the sound absorption coefficient. If the opening rate is too high, the noise reduction coefficient of the material will decrease, so the opening rate needs to be limited to an appropriate range.

[0009] Furthermore, the first through holes are arranged in a square array or an equilateral triangle array. The first through holes are arranged regularly to ensure that the sound absorption performance of each part of the material is consistent.

[0010] Furthermore, the first through hole is a circular hole, the aperture of the first through hole is 0.1-1 mm, and the distance between adjacent holes is 10-100 mm. The first through hole is a circular hole with a small aperture, which is conducive to widening the sound absorption frequency coverage range, but when the aperture is too small, the noise reduction coefficient will be significantly reduced.

[0011] Furthermore, the opening rate of the perforated aluminum plate is 10% to 30%.

[0012] Furthermore, the second through hole is a circular hole, the diameter of the second through hole is 1-5 mm, and the distance between adjacent holes is 1-5 mm.

[0013] Within the limited range of opening ratio and aperture, perforated aluminum plate has a good sound absorption effect on low-frequency and high-frequency sound waves. After the perforated aluminum plate is compounded with the perforated foam aluminum plate, the sound absorption effect has a superimposed effect, and has a good sound absorption performance in the entire frequency range of 200~4000Hz.

[0014] Furthermore, the porosity of the closed-cell aluminum foam is 70% to 80%, and the pore size is 2 to 5 mm. The porosity and pore size of the closed-cell aluminum foam will affect the sound absorption performance. Defining appropriate porosity and pore size can increase surface diffuse reflection and viscosity effect, thereby improving the sound absorption performance.

[0015] Furthermore, the thickness of the foam aluminum plate is 10-30 mm, and the thickness of the perforated aluminum plate is 1-8 mm. The overall thickness of the composite sound-absorbing board is relatively thin, and increasing the thickness has limited effect on the improvement of the noise reduction coefficient, and has the advantages of light weight and low cost.

[0016] The present invention also provides a method for preparing the perforated foam aluminum composite sound-absorbing board, comprising the following steps: Prepare closed-cell foam aluminum, cut it into foam aluminum plates of designed size, and form a plurality of first through holes penetrating along the thickness direction on the foam aluminum plates by laser punching or punching; Prepare non-woven fabric, cut it into the same size as the foam aluminum plate, and apply adhesive on the non-woven fabric; Prepare a perforated aluminum plate, cut it into the same size as the foam aluminum plate, set the foam aluminum plate and the perforated aluminum plate on both sides of the non-woven fabric respectively, pressurize and bond them to obtain a perforated foam aluminum composite sound-absorbing panel.

[0017] The above preparation method uses non-woven fabric as an adhesive layer to bond the foam aluminum plate and the perforated aluminum plate together, thereby preventing the adhesive from entering the through holes or the pores of the foam aluminum, reducing the adverse effects of the composite process on the sound absorption performance of the material, and achieving the superposition of multi-media sound absorption effects; and the process method is simple to operate, and material bonding can be achieved by applying a slight pressure, without the need for heating and curing.

[0018] In summary, the present invention has the following beneficial effects: (1) The present invention composites the perforated foam aluminum plate with the perforated aluminum plate, so that the sound absorption effects of the two sound-absorbing materials have a superimposed effect, broadens the sound absorption frequency coverage range of the material, reduces the difference in sound absorption coefficients of each frequency band, and improves the noise reduction coefficient.

[0019] (2) The present invention arranges the first through holes on the foam aluminum plate and the second through holes on the perforated aluminum plate in a staggered manner, thereby extending the transmission path of the sound waves in the composite sound-absorbing panel, thereby enhancing the sound absorption effect.

[0020] (3) The present invention limits the structure of the pores of the foam aluminum plate, the first through holes, and the second through holes of the perforated aluminum plate, thereby obtaining a structure with the best sound absorption effect, so that the composite sound-absorbing panel has multiple sound absorption peaks with increased peak width, and has a good sound absorption effect in the entire frequency range of 200~4000Hz.

[0021] (4) The present invention uses non-woven fabric to bond the foam aluminum plate and the perforated aluminum plate together, thereby avoiding the adverse effect of the adhesive clogging the holes on the sound absorption performance of the material, while simplifying the process operation, which is conducive to industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of a perforated foam aluminum composite sound-absorbing panel in a specific embodiment of the present invention.

[0023] Figure 2 It is a sound absorption coefficient-frequency curve diagram of the perforated foam aluminum composite sound-absorbing board of Example 1 of the present invention.

[0024] Figure 3 It is a sound absorption coefficient-frequency curve diagram of the perforated foam aluminum composite sound-absorbing board of Example 2 of the present invention.

[0025] Figure 4 It is a sound absorption coefficient-frequency curve diagram of the perforated foam aluminum composite sound-absorbing board of Example 3 of the present invention.

[0026] Figure 5 It is a sound absorption coefficient-frequency curve diagram of the perforated foam aluminum composite sound-absorbing board of Example 4 of the present invention.

[0027] Figure 6 It is a sound absorption coefficient-frequency curve diagram of the perforated foam aluminum composite sound-absorbing board of Example 5 of the present invention.

[0028] Figure 7 It is a sound absorption coefficient-frequency curve diagram of the perforated foam aluminum composite sound-absorbing board of Example 6 of the present invention.

[0029] Figure 8 It is a sound absorption coefficient-frequency curve diagram of the perforated foam aluminum composite sound-absorbing board of Example 7 of the present invention.

[0030] Fig. 9 It is a sound absorption coefficient-frequency curve diagram of the perforated foam aluminum composite sound-absorbing board of Example 8 of the present invention.

[0031] Fig.10 It is a sound absorption coefficient-frequency curve diagram of the perforated foam aluminum composite sound-absorbing board of Example 9 of the present invention.

[0032] Fig.11 It is a sound absorption coefficient-frequency curve of the closed-cell foam aluminum plate of comparative example 1 of the present invention.

[0033] Fig.12 It is a sound absorption coefficient-frequency curve of the perforated foam aluminum plate of comparative example 2 of the present invention.

[0034] Fig.13 It is a sound absorption coefficient-frequency curve diagram of the perforated foam aluminum composite sound-absorbing board of comparative example 3 of the present invention.

[0035] Fig.14 This is a graph of the sound absorption coefficient-frequency curve of the perforated foam aluminum composite sound-absorbing board of comparative example 4 of the present invention Description of reference numerals: 1-foam aluminum plate, 2-non-woven fabric, 3-perforated aluminum plate, 4-first through hole, 5-second through hole. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0037] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0038] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present application description and examples are exemplary only.

[0039] The specific embodiment of the present invention provides a perforated foam aluminum composite sound-absorbing board, and its typical structure is as follows: Figure 1 As shown, it includes a foam aluminum plate 1, a non-woven fabric 2 and a perforated aluminum plate 3 arranged in layers. The thickness of the foam aluminum plate 1 is 10-30 mm, and the material is closed-cell foam aluminum, preferably with a porosity of 70%-80% and a pore size of 2-5 mm. A plurality of first through holes 4 are evenly distributed on the foam aluminum plate 1 along the thickness direction, so that some holes of the closed-cell foam aluminum are connected to produce a viscous effect. The first through holes 4 are arranged in a square array or an equilateral triangle array to ensure that the sound absorption performance of each part of the material is consistent; preferably, the opening rate of the foam aluminum plate 1 is 1%-10%, the first through hole 4 is a circular hole with a hole diameter of 0.1-1 mm, and the spacing between adjacent holes is 10-100 mm. The thickness of the perforated aluminum plate 3 is 1-8 mm, and it is provided with a plurality of evenly distributed second through holes 5. Preferably, the opening rate of the perforated aluminum plate 3 is 10%-30%, the second through hole 5 is a circular hole with a hole diameter of 1-5 mm, and the spacing between adjacent holes is 1-5 mm. The non-woven fabric 2 is used as an adhesive layer, on which an adhesive is coated. The foam aluminum plate 1 and the perforated aluminum plate 3 are arranged on both sides of the non-woven fabric 2 and bonded together by the non-woven fabric 2. The foam aluminum plate 1 has a good sound absorption effect for medium-frequency sound waves, while the perforated aluminum plate 3 has a better sound absorption effect for low-frequency and high-frequency sound waves. After the foam aluminum plate 1 and the perforated aluminum plate 3 are composited, the sound absorption effect has a superposition effect, which broadens the sound absorption frequency coverage range of the material, reduces the difference in sound absorption coefficients of each frequency band, and improves the noise reduction coefficient. Preferably, the first through hole 4 on the foam aluminum plate 1 and the second through hole 5 on the perforated aluminum plate 3 are staggered, so that the sound waves can be reflected and absorbed multiple times on the composite sound-absorbing plate, extending the transmission path of the sound waves, thereby enhancing the sound absorption effect.

[0040] The preparation process of the perforated aluminum foam composite sound-absorbing panel is as follows: (1) Prepare closed-cell foam aluminum, cut it into a foam aluminum plate 1 of designed size, and form a plurality of first through holes 4 penetrating along the thickness direction on the foam aluminum plate by laser punching or punching.

[0041] (2) Prepare non-woven fabric 2, cut it into the same size as the foam aluminum plate, and brush adhesive on the non-woven fabric 2.

[0042] (3) Prepare a perforated aluminum plate 3, cut it into the same size as the foam aluminum plate, place the foam aluminum plate 1 and the perforated aluminum plate 3 on both sides of the non-woven fabric 2, respectively, and apply pressure to achieve bonding to obtain a perforated foam aluminum composite sound-absorbing panel.

[0043] The above preparation method uses non-woven fabric as the bonding layer to prevent the adhesive from entering the through holes or the pores of the foamed aluminum, thereby reducing the adverse effects of the composite process on the sound absorption performance of the material; and the process method is simple to operate, and the material bonding can be achieved with a slight pressure, which is convenient for industrial production.

[0044] The technical effects of the present invention are described below in conjunction with specific embodiments.

[0045] Example 1 The perforated aluminum foam composite sound-absorbing panel was prepared, and the process steps were as follows: prepare closed-cell aluminum foam with a porosity of 75% and an average pore diameter of 4mm; cut it into a 20mm thick, 100×100mm long and wide aluminum foam plate; use laser punching to form multiple through holes penetrating along the thickness direction on the aluminum foam plate, with an opening rate of 5%, a square array of through holes, a pore diameter of 0.5mm, and a spacing of 50mm between adjacent holes. Prepare a 2mm thick perforated aluminum plate, cut it into a 100×100mm long and wide sample, the opening rate of the perforated aluminum plate is 25%, the through hole diameter is 2mm, and the spacing between adjacent holes is 3mm. Cut a 100×100mm non-woven fabric, brush it with adhesive, set the aluminum foam plate and the perforated aluminum plate on both sides of the non-woven fabric, and arrange the through holes on the aluminum foam plate and the through holes on the perforated aluminum plate in a staggered arrangement; pressurize to achieve bonding, and obtain a perforated aluminum foam composite sound-absorbing panel.

[0046] The sound absorption coefficient of the sample in this embodiment was tested at different frequencies. The results are as follows: Figure 2 As shown, its noise reduction coefficient (NRC) is 0.82.

[0047] Example 2 A perforated foam aluminum composite sound-absorbing board was prepared. The difference between this embodiment and embodiment 1 is that the opening rate of the foam aluminum board is 10%, and the distance between adjacent holes is 10 mm. Other material characteristics and process steps are the same.

[0048] The sound absorption coefficient of the sample in this embodiment was tested at different frequencies. The results are as follows: Figure 3 As shown, the NRC is 0.77.

[0049] Example 3 A perforated foam aluminum composite sound-absorbing board was prepared. The difference between this embodiment and embodiment 1 is that the opening rate of the foam aluminum board is 3%, the through holes are arranged in a regular triangle array, the hole diameter is 1 mm, and the distance between adjacent holes is 30 mm. Other material characteristics and process steps are the same.

[0050] The sound absorption coefficient of the sample in this embodiment was tested at different frequencies. The results are as follows: Figure 4 As shown, the NRC is 0.79.

[0051] Example 4 A perforated aluminum foam composite sound-absorbing board was prepared. The difference between this embodiment and embodiment 1 is that the opening rate of the perforated aluminum board is 30%, the through hole diameter is 1 mm, and the distance between adjacent holes is 2 mm. Other material characteristics and process steps are the same.

[0052] The sound absorption coefficient of the sample in this embodiment was tested at different frequencies. The results are as follows: Figure 5 As shown, the NRC is 0.79.

[0053] Example 5 A perforated aluminum foam composite sound-absorbing board was prepared. The difference between this embodiment and embodiment 1 is that the porosity of the aluminum foam board is 80%, and the pore diameter is 3 mm. Other material characteristics and process steps are the same.

[0054] The sound absorption coefficient of the sample in this embodiment was tested at different frequencies. The results are as follows: Figure 6 As shown, the NRC is 0.75.

[0055] Example 6 A perforated foam aluminum composite sound-absorbing board was prepared. The difference between this embodiment and embodiment 1 is that the thickness of the foam aluminum board is 30 mm, and the thickness of the perforated aluminum board is 5 mm. Other material characteristics and process steps are the same.

[0056] The sound absorption coefficient of the sample in this embodiment was tested at different frequencies. The results are as follows: Figure 7 As shown, the NRC is 0.81.

[0057] Example 7 A perforated foam aluminum composite sound-absorbing board was prepared. The difference between this embodiment and embodiment 1 is that the foam aluminum board has a thickness of 30 mm, an opening rate of 1%, a through hole diameter of 0.2 mm, and a spacing between adjacent holes of 100 mm. Other material characteristics and process steps are the same.

[0058] The sound absorption coefficient of the sample in this embodiment was tested at different frequencies. The results are as follows: Figure 8 As shown, the NRC is 0.72.

[0059] Example 8 A perforated aluminum foam composite sound-absorbing board was prepared. The difference between this embodiment and embodiment 1 is that the thickness of the perforated aluminum board is 5 mm, the opening rate is 15%, and the distance between adjacent holes is 5 mm. Other material characteristics and process steps are the same.

[0060] The sound absorption coefficient of the sample in this embodiment was tested at different frequencies. The results are as follows: Fig. 9 As shown, the NRC is 0.81.

[0061] Example 9 A perforated foam aluminum composite sound-absorbing board was prepared. The difference between this embodiment and embodiment 1 is that the opening rate of the foam aluminum board is 7%, the through hole diameter is 0.8 mm, and the distance between adjacent holes is 20 mm; the opening rate of the perforated aluminum board is 20%, the through hole diameter is 3 mm, and the distance between adjacent holes is 5 mm. Other material characteristics and process steps are the same.

[0062] The sound absorption coefficient of the sample in this embodiment was tested at different frequencies. The results are as follows: Fig.10 As shown, the NRC is 0.78.

[0063] Comparative Example 1 Prepare a closed-cell aluminum foam plate with a porosity of 75% and an average pore diameter of 4 mm, and cut it into plates with a thickness of 20 mm and a length and width of 100×100 mm.

[0064] The sound absorption coefficient of the comparative sample at different frequencies was tested. Fig.11 As shown, the NRC is 0.31.

[0065] Comparative Example 2 Prepare a perforated foam aluminum plate, prepare a closed-cell foam aluminum with a porosity of 75% and an average pore diameter of 4 mm, and cut it into a foam aluminum plate with a thickness of 20 mm and a length and width of 100×100 mm; use laser punching to form a plurality of through holes penetrating along the thickness direction on the foam aluminum plate, the opening rate is 5%, the through holes are arranged in a square array, the pore diameter is 0.5 mm, and the distance between adjacent holes is 50 mm.

[0066] The sound absorption coefficient of the comparative sample at different frequencies was tested. Fig.12 As shown, the NRC is 0.38.

[0067] Comparative Example 3 The perforated aluminum foam composite sound-absorbing board was prepared. The difference between this comparative example and Example 1 is that when the aluminum foam board and the perforated aluminum board are bonded together by the non-woven fabric, the through holes on the aluminum foam board are aligned with the through holes on the perforated aluminum board, and all the through holes on the aluminum foam board are covered by the through holes on the perforated aluminum board. Other material characteristics and process steps are the same.

[0068] The sound absorption coefficient of the comparative sample at different frequencies was tested. Fig.13 As shown, the NRC is 0.61.

[0069] Comparative Example 4 The perforated foam aluminum composite sound-absorbing board was prepared. The difference between this comparative example and Example 3 is that the foam aluminum board and the perforated aluminum board are bonded together by a liquid adhesive. Other material characteristics and process steps are the same.

[0070] The sound absorption coefficient of the comparative sample at different frequencies was tested. Fig.14 As shown, the NRC is 0.70.

[0071] Although the disclosure is disclosed as above, the protection scope of the disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A perforated foam aluminum composite sound-absorbing board, characterized in that: The invention comprises a foam aluminum plate, a non-woven fabric and a perforated aluminum plate which are stacked. The material of the foam aluminum plate is closed-cell foam aluminum. The foam aluminum plate is provided with a plurality of first through holes penetrating along the thickness direction, and each of the first through holes is evenly distributed on the foam aluminum plate. The perforated aluminum plate is provided with a plurality of second through holes, and each of the second through holes is evenly distributed on the perforated aluminum plate. The non-woven fabric is coated with an adhesive, and the foam aluminum plate and the perforated aluminum plate are bonded together by the non-woven fabric.

2. The perforated foam aluminum composite sound-absorbing board according to claim 1, characterized in that: The first through holes and the second through holes are arranged in a staggered manner.

3. The perforated foam aluminum composite sound-absorbing board according to claim 2, characterized in that: The opening rate of the foam aluminum plate is 1% to 10%.

4. The perforated foam aluminum composite sound-absorbing board according to claim 3, characterized in that: The first through holes are arranged in a square array or a regular triangle array.

5. The perforated foam aluminum composite sound-absorbing board according to claim 4, characterized in that: The first through hole is a circular hole, the hole diameter of the first through hole is 0.1-1 mm, and the distance between adjacent holes is 10-100 mm.

6. The perforated foam aluminum composite sound-absorbing board according to claim 2, characterized in that: The opening rate of the perforated aluminum plate is 10% to 30%.

7. The perforated foam aluminum composite sound-absorbing board according to claim 6, characterized in that: The second through hole is a circular hole, the hole diameter of the second through hole is 1-5 mm, and the distance between adjacent holes is 1-5 mm.

8. The perforated foam aluminum composite sound-absorbing board according to claim 1, characterized in that: The closed-cell aluminum foam has a porosity of 70% to 80% and a cell diameter of 2 to 5 mm.

9. The perforated foam aluminum composite sound-absorbing board according to any one of claims 1 to 8, characterized in that: The thickness of the foam aluminum plate is 10-30 mm, and the thickness of the perforated aluminum plate is 1-8 mm.

10. A method for preparing a perforated foam aluminum composite sound-absorbing board according to any one of claims 1 to 9, characterized in that: The following steps are involved: Prepare closed-cell foam aluminum, cut it into foam aluminum plates of designed size, and form a plurality of first through holes penetrating along the thickness direction on the foam aluminum plates by laser punching or punching; Prepare non-woven fabric, cut it into the same size as the foam aluminum plate, and apply adhesive on the non-woven fabric; Prepare a perforated aluminum plate, cut it into the same size as the foam aluminum plate, set the foam aluminum plate and the perforated aluminum plate on both sides of the non-woven fabric respectively, pressurize and bond them to obtain a perforated foam aluminum composite sound-absorbing panel.

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