Sound-absorbing structure, automotive interior parts and automobiles

Abstract

To provide a sound absorbing structure that exerts high sound-absorbing performance in a frequency range of 300 Hz or less, a vehicle interior component, and a vehicle.SOLUTION: A sound absorbing structure 1, where a porous body sheet 10 and a grid plate 20 made of resin or metal are laminated in this order, is provided. The porous body sheet is fixed to the grid plate at a region facing at least a portion of grid points 21 of the grid plate, and regions other than the fixed region is displaceable in a sound incident direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sound absorbing structure, an interior part for an automobile, and an automobile. [Background technology]

[0002] There are many sound sources within an automobile. To address the demand for quietness from noise both inside and outside the vehicle, automobiles are equipped with various soundproofing measures. In particular, specialized soundproofing covers with excellent sound absorption and insulation performance are used for loud noise-generating components (intrinsic sound sources) such as the engine, transmission, and drivetrain. Furthermore, since reducing interior noise is directly linked to the value (luxury) of a vehicle, there is a high demand for noise-reducing components in automobiles. For example, even within an automobile's cabin, cavity resonance can be induced by engine vibration, intake and exhaust noise, road irritation, etc., resulting in problems such as muffled noise and road noise. Therefore, measures to reduce such noise are essential. While various soundproofing components have been used in automobile interiors, such as roof trim, further performance improvements are required. Furthermore, from the perspective of improving fuel economy, it is preferable for soundproofing measures to also meet the demand for weight reduction.

[0003] Various sound-absorbing materials are known for their construction. For example, foams such as urethane foam have traditionally been used as sound-absorbing materials, and are capable of absorbing airborne noise in the high-frequency range. Other examples include porous materials such as glass wool and rock wool, which are used to absorb noise in the frequency range above 500 Hz.

[0004] On the other hand, for noise below 500Hz, attempts have been made to increase the thickness of the porous sound-absorbing material, or to create an air layer behind the sound-absorbing material for even lower frequency ranges. However, in order to achieve sufficient sound absorption, problems have arisen, such as the weight being heavy and the space required being large.

[0005] To address this issue, for example, Patent Document 1 discloses a sound-absorbing material that is integrally molded by laminating a foam and a porous material such as glass wool or rock wool. This type of configuration is said to have a high sound-absorbing effect in the low frequency range and excellent vibration damping properties. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-316364 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the inventors have found through their investigations that even if the technology described in Patent Document 1 is used, it is not possible to achieve sufficient sound absorption performance in the frequency range of 300 Hz or less. Therefore, an object of the present invention is to provide a means that makes it possible to achieve high sound absorption performance in the frequency range of 300 Hz or less. [Means for solving the problem]

[0008] The present inventors have conducted extensive research in light of the above-mentioned problems, and as a result have discovered that by laminating a porous sheet and a lattice plate made of resin or metal and allowing the porous sheet to be displaced in the direction of sound incidence, a sound-absorbing structure that exhibits high sound-absorbing performance in the frequency range of 300 Hz or less can be obtained, thereby completing the present invention.

[0009] That is, the present invention provides a sound-absorbing structure in which a porous body sheet and a lattice plate made of resin or metal are laminated in this order, the porous body sheet is fixed to the lattice plate at a portion facing at least some of the lattice points of the lattice plate, and the portion other than the fixed portion is displaceable in the direction of incident sound. [Effects of the Invention]

[0010] According to the present invention, when sound is incident on the porous sheet, the portions of the porous sheet that are not fixed to the lattice plate are displaced in the direction of the sound, generating vibrations that cancel out the low-frequency components of the sound. As a result, sound absorption performance can be improved, particularly in the low-frequency range below 300 Hz. [Brief explanation of the drawings]

[0011] [Figure 1] 1A is a perspective view schematically illustrating an outline of a sound absorbing structure according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view of the sound absorbing structure according to one embodiment of the present invention. [Figure 2] FIG. 10 is a perspective view schematically illustrating an outline of a sound absorbing structure according to another embodiment of the present invention. [Figure 3] FIG. 1 shows an outline of (a) the device used to measure the sound absorption coefficient and (b) the device used to measure the membrane vibration acceleration. [Figure 4] FIG. 2 is a diagram showing the sound absorption coefficient and membrane vibration acceleration of the sound absorbing structure produced in Example 1. [Figure 5] 1 is a photograph of the sound-absorbing structure samples produced in Examples 2-1 and 2-2. [Figure 6] 1 is a graph showing the results of measuring the sound absorption coefficient of the sound absorbing structures produced in Comparative Examples 2-1 and 2-2 and Examples 2-1 and 2-2. [Figure 7] FIG. 1 is a diagram showing the size and arrangement of openings in a lattice plate used in a sound-absorbing structure fabricated in the Examples section described later, as well as the opening area. [Figure 8A] 10 is a graph showing the results of measuring the sound absorption coefficient of the sound absorbing structures produced in Examples 3-1 to 3-6. [Figure 8B] 1 is a graph showing the results of measuring the sound absorption coefficient of the sound absorbing structures produced in Example 2-1, Examples 3-2 to 3-4, and Example 3-7. [Figure 9] 10 is a graph showing the results of measuring the sound absorption coefficient of the sound absorbing structures produced in Examples 4-1 to 4-6. [Figure 10] FIG. 2 is a diagram showing the adhesive positions of the porous sheet and the lattice plate in the sound-absorbing structure produced in the Examples section described later. [Figure 11]10 is a graph showing the results of measuring the sound absorption coefficient of the sound absorbing structures produced in Examples 5-1 to 5-5 and Comparative Examples 5-1 to 5-3. DETAILED DESCRIPTION OF THE INVENTION

[0012] One aspect of the present invention is a sound-absorbing structure in which a porous body sheet and a lattice plate made of resin or metal are laminated in this order, the porous body sheet is fixed to the lattice plate at portions facing at least some of the lattice points of the lattice plate, and portions other than the fixed portions are displaceable in the direction of incident sound.

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the technical scope of the present invention is not limited to the following embodiments. Note that the dimensional ratios in the drawings are exaggerated for the sake of explanation and may differ from the actual ratios. In this specification, the range "X to Y" means "X or more and Y or less." Furthermore, unless otherwise specified, operations and measurements of physical properties, etc. are performed under conditions of room temperature (20 to 25°C) and relative humidity of 40 to 50%.

[0014] Fig. 1(a) is a perspective view schematically illustrating an outline of a sound absorbing structure according to one embodiment of the present invention, and Fig. 1(b) is a cross-sectional view of the sound absorbing structure according to one embodiment of the present invention.

[0015] As shown in Figures 1(a) and 1(b), a sound-absorbing structure 1 according to one embodiment of the present invention has a configuration in which a porous body sheet 10 and a lattice plate 20 are laminated in this order from the sound incident side indicated by the arrow in Figure 1(b). The lattice plate 20 is made of resin or metal and has regularly-spaced openings 22. The porous body sheet 10 is fixed to the lattice plate at portions (fixing positions) 21a that face at least some of the intersections (lattice points) 21 of the lattice plate 20, and is free at other portions, allowing it to move in the direction of incident sound.

[0016] When sound is incident on the porous body sheet 10, the portion of the porous body sheet 10 that is not fixed to the lattice plate is displaced in the direction of the sound incidence, causing membrane vibration that cancels out the low-frequency components of the sound. This is thought to attenuate the low-frequency components of the sound and produce a sound-absorbing effect. Therefore, even if the porous body sheet 10 and the lattice plate 20 are stacked in the reverse order to that of this embodiment, it is thought that the same sound-absorbing effect as described above will be produced.

[0017] The sound-absorbing structure 1 of this embodiment can achieve excellent sound-absorbing performance with a very simple configuration. In particular, despite its lightweight and simple configuration, it can exhibit high sound-absorbing performance in a frequency range of 300 Hz or less (for example, a frequency range of 50 to 300 Hz or a frequency range of 100 to 300 Hz), a characteristic that has not been achieved with conventional technologies.

[0018] It has been known that when sound enters a porous sheet with open cells, such as glass wool or urethane foam, the sound waves are affected by friction with the surrounding walls and viscous resistance within the pores, resulting in a portion of the sound energy being dissipated as heat energy, resulting in sound absorption. However, because sound absorption characteristics are generally low in the low frequency range and high in the high frequency range, it has been difficult to achieve sufficient sound absorption in the low frequency range below 300 Hz, such as vibrations caused by cavity resonance within the vehicle body. Therefore, in order to improve sound absorption characteristics in the low frequency range, it was thought that the thickness of the porous sheet needed to be increased to correspond to the longer wavelength of the sound waves.

[0019] Furthermore, in conventional soundproofing materials, there has been a trend in which soundproofing performance improves as the density of the constituent materials increases, and for this reason, it has been common knowledge in the prior art that in order to improve soundproofing performance, it is necessary to increase the density of the soundproofing material, i.e., increase its weight.

[0020] In contrast, the sound-absorbing structure of this embodiment exhibits sound-absorbing performance by canceling out low-frequency sounds through membrane vibration of the porous sheet. Therefore, contrary to conventional performance trends, it can have excellent sound-absorbing performance in the frequency range of 300 Hz or less, even though it is lightweight and thin.

[0021] FIG. 2 is a perspective view schematically illustrating a sound-absorbing structure according to another embodiment of the present invention. Similar to the sound-absorbing structure 1 illustrated in FIGS. 1(a) and 1(b), the sound-absorbing structure 2 illustrated in FIG. 2 includes a porous body sheet 10 and a lattice plate 20 laminated in this order from the sound-incident side. The porous body sheet 10 is fixed to the lattice plate 20 at portions facing at least some of the lattice points, while remaining unfixed at other portions, allowing for displacement in the direction of sound incidence. Additionally, the sound-absorbing structure 2 illustrated in FIG. 2 also includes a film 30 laminated on the radiation / transmission side of the lattice plate 20, which is adhered to the lattice plate 20. This allows the film 30 to vibrate, changing the sound-absorbing characteristics of the sound-absorbing structure 2. For example, the sound absorption coefficient in the 200-700 Hz frequency range can be increased, enhancing sound-absorbing performance in that frequency range. Therefore, the sound-absorbing characteristics can be adjusted according to the application. In this case, it is preferable that the film 30 is bonded to the lattice plate 20 in a portion other than the outer periphery of the lattice plate 20 .

[0022] Below, we will explain in more detail the components of the sound absorbing structures 1 and 2. In this specification, "sound absorbing" means reducing reflected sound or absorbing sound (acoustics).

[0023] (Porous sheet) Porous material sheets have sound absorption properties due to the presence of continuous pores, and attenuate sound by vibrating in the direction of sound incidence. There are no particular restrictions on the materials constituting the porous material sheet, and known materials can be used. Examples include porous material sheets made of fibrous materials, resin foams, metals, ceramics, glass, etc. Among these, resin foams are preferred because of their light weight.

[0024] The fibrous body is not particularly limited as long as it is an aggregate of fibers having voids on the surface and inside thereof, and either a woven fabric or a nonwoven fabric such as felt can be used. Furthermore, the fibrous body may be made of organic fibers such as resin fibers, or inorganic fibers such as glass fibers.

[0025] Examples of resin foams include polyolefin foams such as polyurethane foam (hereinafter also referred to as urethane foam), polyethylene foam, and polypropylene foam; polystyrene foam; polyamide foam; polyester foams such as polyethylene terephthalate (PET) foam and polybutylene terephthalate (PBT); (meth)acrylic foam; phenolic foam; polyvinyl chloride foam; polyimide foam; silicone resin foam; urea resin foam; melamine resin foam; ethylene propylene diene rubber (EPDM) foam; styrene butadiene rubber (SBR) foam; nitrile butadiene rubber (NBR) foam; ethylene-vinyl acetate copolymer (EVA) foam; ethylene-acrylic acid copolymer foam; and ethylene-ethyl acrylate copolymer (EEA) foam. Among these, polyurethane foams are preferred from the viewpoint of sound absorption performance. These foams may be soft, semi-rigid, or rigid.

[0026] The thickness of the porous sheet is not particularly limited, but is preferably 1 to 100 mm, more preferably 5 to 50 mm, from the viewpoint of the sound absorbing effect of the sound absorbing structure. The density of the porous sheet is also not particularly limited, but is preferably 3 to 150 kg / m 3 This is preferable from the viewpoint of weight reduction.

[0027] (lattice plate) The lattice plate is a resin or metal plate with lattice-like compartments that supports the porous sheet at at least some of the lattice intersections (lattice points). By making the lattice plate from resin or metal, it becomes easier to adjust the Young's modulus of the lattice plate to a desired value, and it becomes possible to improve the sound absorption characteristics of the sound absorbing structure.

[0028] The resin material constituting the grid plate is not particularly limited, but conventionally known thermoplastic resins or thermosetting resins can be used.

[0029] Examples of thermoplastic resins include polyethylene (e.g., low-density polyethylene, high-density polyethylene, etc.), polyolefin resins such as polypropylene, polyvinyl chloride resins, acrylic resins, methacrylic resins, acrylonitrile-butadiene-styrene resins, vinyl acetate resins, ethylene-vinyl acetate resins, and styrene-butadiene resins. Examples of thermosetting resins that can be used include urethane resins, melamine resins, thermosetting acrylic resins, urea resins, phenolic resins, resorcinol resins, alkylresorcinol resins, epoxy resins, and thermosetting polyesters. Resin precursors that produce these resins, such as prepolymers, oligomers, and monomers, may also be used, including urethane resin prepolymers, urea resin prepolymers (initial condensates), phenolic resin prepolymers (initial condensates), diallyl phthalate prepolymers, acrylic oligomers, polyisocyanates, methacrylic ester monomers, and diallyl phthalate monomers. Among these, thermoplastic resins are preferred from the viewpoint of ease of molding, and polyolefin resins are particularly preferred due to their lightweight, excellent durability, and low cost.

[0030] Examples of the metal material include copper, aluminum, titanium, magnesium, tungsten, iron, chromium, and alloys thereof. Stainless steel (SUS) may also be used as the metal material.

[0031] It is more preferable that the lattice plate 20 has a plurality of openings 22 of the same shape arranged in a regular pattern. This configuration facilitates manufacturing, and the presence of a large number of openings of the same shape makes it possible to specifically exhibit sound absorption performance for sound waves in a desired frequency range. In this case, there are no particular restrictions on the ratio of the area of ​​the openings 22 to the area of ​​the lattice plate 20. The shape of the openings 22 is not limited to a square, and may be rectangular, hexagonal, triangular, etc.

[0032] There are no particular limitations on the size of the openings 22 in the lattice plate 20. For example, if the openings are square, the length of one side is, for example, 1 to 50 mm, preferably 2 to 40 mm, and more preferably 3 to 39 mm. This can improve the sound absorption characteristics in the frequency range of 300 Hz or less.

[0033] The area of ​​each opening 22 of the lattice plate 20 (opening area) is not particularly limited, but is preferably 10 to 1500 mm from the viewpoint of obtaining high sound absorption characteristics. 2 In particular, in the sound absorbing structure 1 shown in Fig. 1(a) and (b) which is composed of a porous sheet 10 and a lattice plate 20, the opening area is 10 mm 2 If the opening area is 1500mm or more, the sound absorption coefficient of 200Hz or less can be improved. 2 If it is equal to or less than this, the sound absorption coefficient in the frequency range of 200 to 300 Hz can be improved.

[0034] On the other hand, in the sound absorbing structure 2 of FIG. 2, in addition to the porous sheet 10 and the lattice plate 20, a film 30 is bonded to the radiation / transmission side of the lattice plate 20. The opening area of ​​the opening 22 of the lattice plate 20 is 10 to 225 mm. 2 It is more preferable that the opening area is 10 mm 2 If the opening area is 225mm or more, the sound absorption coefficient below 200Hz can be improved. 2 If it is equal to or less than this, the sound absorption coefficient in the frequency range of 200 to 300 Hz can be improved.

[0035] The thickness of the lattice plate 20 is not particularly limited, but is, for example, 0.1 to 10 mm, preferably 0.5 to 5 mm. If it is 0.1 mm or more, the effects of the present invention can be more easily obtained. Also, if it is 10 mm or less, it is preferable from the viewpoint of weight reduction.

[0036] In the sound-absorbing structure according to this embodiment, the bonding positions (fixing positions) between the porous body sheet and the lattice plate are not particularly limited, as long as the porous body sheet is fixed to the lattice plate at portions facing at least some of the lattice points, and the remaining portions are capable of vibrating in the direction of sound incidence. As long as the above-mentioned bonding positions (fixing positions) include portions facing at least some of the lattice points, and portions of the porous body sheet other than the bonding positions are capable of vibrating in the direction of sound incidence, the porous body sheet may be further bonded (fixed) to portions other than those facing the lattice points. Similarly, the bonding area is not particularly limited, as long as it satisfies the above requirements.

[0037] As an example, as shown by the bold lines in the photograph of the sound-absorbing structure sample in Figure 10(a), the porous body sheet can be fixed to the lattice plate at the positions where the lattice is present. Alternatively, as shown in Figures 10(b) to 10(d), the porous body sheet can be fixed to the lattice plate at an arbitrarily selected portion of the positions where the lattice is present. Alternatively, as shown in Figure 10(e), the porous body sheet can be fixed to the lattice plate at some of the lattice points. The adhesive area is not particularly limited and can be selected arbitrarily. Figures 10(a) to 10(e) are photographs of sound-absorbing structure samples in which a 90 mm x 90 mm porous body sheet is laminated with a lattice plate with a line width of 7 mm and openings of 15 mm x 15 mm. The adhesive positions between the porous body sheet and the lattice plate in each sample are indicated by bold lines.

[0038] 10(a) to (e), the distance between adjacent bonded positions is not particularly limited. To achieve the effects of the present invention more significantly, for example, when the bonded positions are arranged in parallel strips at regular intervals, the distance between adjacent parallel bonded positions is, for example, 200 mm or less, preferably 100 mm or less. For example, when the bonded positions are arranged in a grid pattern, the distance between adjacent parallel bonded positions is, for example, 200 mm or less, preferably 100 mm or less. For example, when the bonded positions are arranged in a dot pattern, the distance between the nearest bonded positions is, for example, 200 mm or less, preferably 100 mm or less.

[0039] (film) The film is provided on the radiation / transmission side of the grid plate and bonded to the grid plate. Preferably, the film is arranged so as to close the opening of the grid plate. The film is preferably bonded to the grid plate in a portion other than the outer periphery of the grid plate.

[0040] The material of the film is not particularly limited, but is preferably lightweight and rigid. For example, polyolefin resins such as polyethylene (e.g., low-density polyethylene, high-density polyethylene, etc.), polypropylene, polyethylene terephthalate resin, polyvinyl chloride resin, polystyrene resin, etc. may be preferably used.

[0041] The thickness of the film is not particularly limited, but is, for example, 1 to 100 μm, preferably 2 to 50 μm. Within this range, the effects of the present invention can be more easily achieved. The size of the film is not particularly limited, but it is preferable that the film be large enough to cover the entire surface of the grid plate.

[0042] The sound absorbing structure according to this embodiment is preferably lightweight. From this viewpoint, the overall density of the sound absorbing structure according to this embodiment is preferably 1 g / cm 3 or less, more preferably 0.5 g / cm 3 More preferably, it is 0.3 g / cm or less. 3 or less, and particularly preferably 0.2 g / cm 3 The sound absorbing structure according to this embodiment is preferably thin. From this viewpoint, the overall thickness of the sound absorbing structure according to this embodiment is preferably 50 mm or less, more preferably 30 mm or less, and even more preferably 20 mm or less.

[0043] When producing the sound-absorbing structure according to this embodiment, the method for bonding the porous body sheet and the lattice plate is not particularly limited, and may be a method using a known adhesive or double-sided tape, or a method using fasteners such as screws or bolts. The method for bonding the lattice plate and the film is also not particularly limited, and may be a method using a known adhesive or double-sided tape.

[0044] The sound-absorbing structure according to this embodiment can be suitably used for absorbing noise from various sound sources. In particular, the sound-absorbing structure according to this embodiment can be configured to be extremely lightweight. Because of this lightweight capability, the sound-absorbing structure according to this embodiment is preferably mounted on a vehicle for use. Examples of application areas include dash insulators, dash panels, floor carpets, spacers, door trim, sound-absorbing structures within door trim, sound-absorbing structures within compartments, instrument panels, instrument center boxes, instrument upper boxes, air conditioner housings, roof trim, sound-absorbing structures within roof trim, sun visors, rear seat air conditioning ducts, cooling ducts for battery cooling systems in battery-powered vehicles, cooling fans, center console trim, sound-absorbing structures within consoles, parcel trim, parcel panels, seat headrests, front seat backs, and rear seat backs. Furthermore, in the trunk, the sound-absorbing structure can be applied to trunk floor trim, trunk boards, trunk side trims, sound-absorbing structures within trim, and drafter covers. It can also be applied inside the vehicle frame or between panels, for example, to pillar trim and fenders. In particular, it is preferable to use it in automotive interior parts because it has excellent sound absorption performance in the frequency range of 300 Hz or less, is lightweight, and allows for a thin overall thickness. [Example]

[0045] The present invention will be described in more detail below with reference to examples, although the technical scope of the present invention is not limited to the following examples.

[0046] <<Sound absorption coefficient measurement>> The sound absorption coefficient was measured in accordance with JIS A 1405-2 (Measurement of sound absorption coefficient and impedance using an acoustic tube - Part 2: Transfer function method). However, a spacer was used to hold the sample, a 10 mm back air gap was created by the spacer behind the sample, and a 5 mm gap was provided between the spacer and the reflector. Figure 3(a) shows a schematic diagram of the sound absorption coefficient measurement device.

[0047] <<Measurement of membrane vibration acceleration>> The membrane vibration acceleration was measured using a laser Doppler vibrometer (Polytec VibroOne). The laser Doppler vibrometer consists of an optical head that emits laser light and a converter that processes the Doppler frequency from the reflected light. A voltage signal proportional to the sample's moving speed was input into an FFT analyzer and converted into acceleration. Figure 3(b) shows a schematic diagram of the membrane vibration acceleration measurement device. Note that both the sound absorption coefficient and membrane vibration acceleration can be measured using the device shown in Figure 3(b).

[0048] <<Creating a sound-absorbing structure>> (Sound absorption effect confirmation: 1) [Example 1] The porous sheet was a 10 mm thick urethane foam (density: approximately 32.1 kg / m 3 , Flow resistance: approx. 36000Ns / m 4 ) was cut to a size of 90 mm x 90 mm.

[0049] A 1.0 mm thick polypropylene (PP) plate (manufactured by Acrylic Eye Co., Ltd., density: 0.9 g / cm 3 ) was cut to 90 mm × 90 mm. This PP plate was cut so that the openings were squares with sides of 15 mm and the spacing between the openings was 7 mm, as shown in Figure 7(d), to create a grid plate (d).

[0050] A lattice plate (d) was laminated on the porous body sheet, and the porous body sheet and the lattice plate (d) were fixed with double-sided tape at the position shown in Figure 10(a) to obtain the sound-absorbing structure of Example 1.

[0051] Using the sound-absorbing structure obtained above, the sound absorption coefficient and membrane vibration acceleration were measured using the device shown in Figure 3(b). The results are shown in Figure 4. As shown in Figure 4, in the sound-absorbing structure of the present invention, the sound absorption coefficient decreases in the frequency range from 100 Hz to around 250 Hz and increases from 800 Hz to 1000 Hz, and the membrane vibration acceleration also shows a similar trend. Since the increase and decrease in the sound absorption coefficient and the membrane vibration acceleration correspond in this way, it is thought that in the sound-absorbing structure of the present invention, sound is absorbed by consuming sound pressure energy due to membrane vibration.

[0052] (Sound absorption effect confirmation: 2) [Comparative Example 2-1] The porous sheet was a 10 mm thick urethane foam (density: approximately 32.1 kg / m 3 , Flow resistance: approx. 36000Ns / m 4 ) was cut to a size of 90 mm x 90 mm. This porous sheet was used as the sound absorbing structure of this comparative example.

[0053] [Comparative Example 2-2] A 1.0 mm thick polypropylene (PP) plate (manufactured by Acrylic Eye Co., Ltd., density: 0.9 g / cm 3 ) was cut to 90 mm x 90 mm. This PP plate was cut so that the openings were squares with sides of 15 mm and the spacing between the openings was 7 mm, as shown in Figure 7(d), to produce a lattice plate (d). This lattice plate (d) was used as the sound-absorbing structure of this comparative example.

[0054] [Example 2-1] A lattice plate (d1) was produced in the same manner as the lattice plate (d) of Comparative Example 2-2, except that the thickness was changed to 2.0 mm. The lattice plate (d1) was laminated on the porous body sheet, and the porous body sheet and the lattice plate (d1) were fixed with double-sided tape at the position shown in Figure 10(a), to form the sound-absorbing structure of this example.

[0055] [Example 2-2] In the sound-absorbing structure of Example 2-1, the lattice plate (d1) was replaced with the lattice plate (d), which was laminated and fixed in the same manner. A 0.01 mm thick polyethylene (PE) film (Hook Poly, manufactured by System Polymer Co., Ltd.) was cut to 100 mm x 100 mm, and this PE film was fixed to the lattice plate (d) with double-sided tape in a portion excluding the outer periphery of the lattice (as shown in Figure 10(a) , the lattice-shaped portion excluding the outer periphery of the lattice), forming the sound-absorbing structure of this example. Figure 5 shows photographs of the sound-absorbing structure samples produced in Examples 2-1 and 2-2.

[0056] The specifications of the above examples and comparative examples are shown in Table 1 below, and the sound absorption coefficient results obtained by evaluating sound absorption performance using the device shown in Figure 3(a) are shown in Figure 6. It was found that the sound-absorbing structures of Examples 2-1 and 2-2 exhibited superior sound-absorbing performance compared to those using urethane foam alone (Comparative Example 2-1) or a lattice board alone (Comparative Example 2-2). It was also found that the sound-absorbing structure of Example 2-2, which further includes a film, can enhance sound-absorbing performance in the 200 to 700 Hz range. Therefore, it was found that a structure without a film can be used in applications where sound-absorbing performance in the 100 to 200 Hz range is particularly important, while a structure with a film can be used in applications where sound-absorbing performance over a relatively wide frequency range from 200 to 700 Hz is required.

[0057] [Table 1]

[0058] (Effect of opening area of ​​grid plate: 1) [Example 3-4] The sound absorbing structure of this example was obtained in the same manner as in the sound absorbing structure of Example 2-1 described above, except that the thickness of the lattice plate was changed to 1.0 mm.

[0059] [Examples 3-1 to 3-3, 3-5, and 3-6] The sound absorbing structures of Examples 3-1 to 3-3, 3-5, and 3-6 were obtained in the same manner as in Example 3-4, except that the opening area of ​​the openings in the lattice plate was changed as shown in Table 2 below. The size and arrangement of the openings in the lattice plate are shown in Figure 7. (a) to (f) in Figure 7 correspond to Examples 3-1 to 3-6, respectively.

[0060] [Examples 3-7] The sound absorbing structure of this example was obtained in the same manner as in the sound absorbing structure of Example 2-1 described above, except that the lattice plate was changed to a 2.0 mm thick SUS plate cut so that the openings were square with sides of 15 mm and the spacing between the openings was 7 mm, as shown in Figure 7(d).

[0061] The specifications of the above examples are shown in Table 2 below, and the sound absorption coefficient results obtained by evaluating the sound absorption performance are shown in Figures 8A and 8B. Figure 8A shows the sound absorption performance of the sound absorbing structures of Examples 3-1 to 3-6, and Figure 8B shows the sound absorption performance of the sound absorbing structures of Examples 2-1, 3-2 to 3-4, and 3-7. In Figure 8B, the sound absorption performance data for Examples 2-1 and 3-2 to 3-4 are the same as those shown in Figures 6 and 8A, respectively. These results show that it is possible to control the frequency range with high sound absorption coefficient and the sound absorption coefficient by changing the opening area of ​​the lattice plate. In the sound absorbing structure composed of a porous sheet and a lattice plate, when the opening area is 10 mm 2 The above-mentioned Examples 3-2 to 3-6 have a high sound absorption coefficient in a low frequency range below 200 Hz. 2 It was found that the following Examples 3-1 to 3-5 had high sound absorption coefficients in the frequency range of 200 to 300 Hz. Furthermore, as shown in Fig. 8B, it was confirmed that the sound absorbing structure of Example 3-7, which uses a metal lattice plate, also exhibits excellent sound absorbing performance, similar to the sound absorbing structures of Examples 2-1 and 3-1 to 3-6, which use a resin lattice plate.

[0062] [Table 2]

[0063] (Effect of the opening area of ​​the grid plate: 2) [Example 4-4] The sound absorbing structure of Example 2-2 described above was used as the sound absorbing structure of this example.

[0064] [Examples 4-1 to 4-3, 4-5, and 4-6] The sound absorbing structures of Examples 4-1 to 4-3, 4-5, and 4-6 were obtained in the same manner as in Example 4-4, except that the opening area of ​​the openings in the lattice plate was changed as shown in Table 3 below. The size and arrangement of the openings in the lattice plate are as shown in Figure 7. (a) to (f) in Figure 7 correspond to Examples 4-1 to 4-6, respectively.

[0065] The specifications of the above example are shown in Table 3 below, and the sound absorption coefficient results obtained by evaluating the sound absorption performance are shown in Figure 9. From these results, it can be seen that in the sound absorbing structure in which a film is further laminated on the radiation / transmission side of the lattice plate, the opening area is 10 mm 2 The above-mentioned Examples 4-2 to 4-6 have a high sound absorption coefficient in the low frequency range below 200 Hz. 2 Above, 225mm 2 It was found that the following Examples 4-2 to 4-4 had high sound absorption coefficients in the frequency range of 200 to 300 Hz.

[0066] [Table 3]

[0067] (Influence of adhesive position) [Example 5-1] The sound absorbing structure of Example 3-4 described above was used as the sound absorbing structure of this example.

[0068] [Examples 5-2 to 5-5] The sound absorbing structures of Examples 5-2 to 5-5 were obtained in the same manner as in the sound absorbing structure of Example 5-1, except that the bonding position between the porous sheet and the lattice plate was changed from the position shown in Figure 10(a) to the positions shown in Figures 10(b) to (d).

[0069] [Comparative Examples 5-1 to 5-3] The sound absorbing structure of Comparative Example 5-1 was obtained in the same manner as in Example 5-1, except that the porous body sheet and the lattice plate were not bonded. In Comparative Example 5-2, only the porous body sheet of Example 5-1 was used as the sound absorbing structure, and in Comparative Example 5-3, only the lattice plate of Example 5-1 was used as the sound absorbing structure.

[0070] The specifications of the above examples and comparative examples are shown in Table 4 below, and the sound absorption coefficient results obtained by evaluating sound absorption performance are shown in Figure 11. As shown in Figure 10, from Example 5-1 to Example 5-5, the gap between the porous body sheet and the lattice plate where they are bonded is gradually increased, and the bonded area is gradually decreased. However, as shown in Figure 11, all examples showed high sound absorption coefficients in the frequency range of 300 Hz or less, and it was found that the influence of the gap and bonded area of ​​the bonded parts was small.

[0071] Therefore, when a large-area sound-absorbing structure is manufactured for use in a vehicle, it is believed that it can be used without any problems even if the distance between adjacent bonding positions is increased to approximately 90 mm.

[0072] [Table 4] [Explanation of symbols]

[0073] 1, 2 Sound-absorbing structure 10 Porous sheet 20 lattice plate 21 grid points 21a Adhesive position (fixed position) 22 Opening 30 films.

Claims

1. A porous sheet and a grid plate made of resin or metal are laminated together, The opening of the lattice plate on the opposite side to the porous body sheet is not closed, the porous sheet is fixed to the lattice plate at a portion facing at least a part of the lattice points of the lattice plate, A sound absorbing method comprising: absorbing sound in a frequency range of 300 Hz or less by causing sound to be incident on the sound absorbing structure from the porous sheet side, wherein portions other than the fixed portions are displaceable in the stacking direction.

2. The opening area of ​​each opening of the lattice plate is 10 mm ２ Over 1500mm ２ 2. The sound absorbing method according to claim 1, wherein:

3. A sound absorption method as described in claim 1 or 2, wherein the sound absorption structure consists only of the porous sheet, the lattice plate, and adhesive, double-sided tape, or fixing devices for fixing them.

4. A sound absorption method described in any one of claims 1 to 3, wherein the thickness of the porous sheet is 5 mm or more, the thickness of the lattice plate is 0.1 to 5 mm, and the overall thickness of the sound absorption structure is 20 mm or less.

5. A sound absorption method described in any one of claims 1 to 4, wherein the lattice plate is not fixed to the porous sheet at its outer periphery.

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