A low-frequency sound absorption structure and its sound absorption method

Abstract

The present invention relates to a low-frequency sound absorption structure and a sound absorption method thereof. The technical features are as follows: The low-frequency sound absorption structure includes a spire and its base. The base is a structure that is closed on the circumference and at the top and open at the bottom. A base cover plate is provided on the top of the base. Dense sound-permeable holes are formed on the surface of the base cover plate. Each sound-permeable hole is short-tubular. The bottom of the sound-permeable hole is located inside the base. An airtight elastic small bubble is bonded to the lower end of the sound-permeable hole. A certain gap is left between each elastic small bubble. Sound-absorbing fibers are laid at the bottom of the base. The present invention absorbs high-frequency sound waves in the sound wave through the spire, and absorbs low-frequency sound through the elastic small balls and the bottom sound-absorbing fibers in the base, achieving the effect of absorbing low-frequency sound waves as a whole. This way of absorbing external noise in different frequency bands realizes the sound absorption function of the sound absorption structure for low-frequency sound waves below 100 Hz without increasing the size, and can be widely used in the construction of anechoic chambers.

Description

Technical Field

[0001] The present invention belongs to the technical field of acoustic sensors, and in particular, to a low-frequency sound absorption structure and a sound absorption method thereof. Background Art

[0002] Sound absorption wedges are a special sound absorption structure suitable for anechoic chambers, usually formed by stacking pure sound absorption cotton blocks, which have good sound absorption effects for medium and high frequencies. Traditional sound absorption structures rely entirely on the pore absorption of sound absorption fibers, and their sound absorption coefficients depend on the specific weight, thickness, density, and porosity of the sound absorption cotton. Usually, the sound absorption coefficient for 1 kHz sound is close to 0.95. Under the condition that these parameters are determined, the lower limit of the sound absorption frequency is determined by the size of the structure. In order to achieve the sound absorption of low-frequency sound waves below 100 Hz, a structure with a larger size needs to be designed, that is, to increase the structure height to lower the lower limit of the sound absorption frequency. For anechoic chambers, the structure should not occupy too much space, otherwise it will occupy too much room volume and increase the manufacturing cost at the same time. This is a bottleneck problem in the construction of current anechoic chambers. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art, and to provide a low-frequency sound absorption structure and a sound absorption method thereof, so as to solve the problem that the existing sound absorption structure cannot absorb sound waves below 100 Hz, and to lower the lower limit frequency of sound absorption to 10 Hz without increasing the occupied space.

[0004] The present invention solves the existing technical problems by adopting the following technical solutions:

[0005] A low-frequency sound absorption structure includes a spire and its base. Dense sound transmission slits are provided on the surface of the spire. The base is a structure that is closed on the periphery and top and open at the bottom. A base cover plate is provided on the top of the base. Dense sound transmission holes are formed on the surface of the base cover plate. Each sound transmission hole is a short tubular shape. The bottom of the sound transmission hole is located inside the base. An elastic small bubble is bonded at the lower end of the sound transmission hole. A certain gap is left between each elastic small bubble. Sound absorption fibers are laid at the bottom of the base.

[0006] Further, the gap left between the elastic small bubbles is less than 6 mm.

[0007] Further, the base is a regular frame structure that is closed on the periphery and top and open at the bottom, and is square or circular.

[0008] Further, the spire is a ramp-shaped structure formed by bonding sound absorption fibers into a block.

[0009] Further, the ramp-shaped structure is a structure of a pair of ramps and a pair of vertical planes, or a structure of four-sided ramps, or a conical structure.

[0010] Furthermore, the spire and the base are installed together by bonding.

[0011] An absorption method for a low-frequency sound absorption structure includes the following steps: When sound waves pass through the dense sound-permeable slits on the surface of the spire, high-frequency sound waves are absorbed. The low-frequency sound waves pass through the sound-permeable holes on the base cover plate, causing each elastic bubble to vibrate, and generating high-frequency sound waves with wavelengths equivalent to the size of the bubbles inside the base. The sound waves generated by the elastic bubbles are out of phase, and the sound waves generated by the elastic bubbles are absorbed by the sound-absorbing fibers at the bottom inside the base, so that the low-frequency sound waves entering the sound-permeable holes are absorbed.

[0012] Furthermore, the lower limit of the absorption frequency is changed by varying the size of the elastic bubbles, and the low-frequency absorption rate is reduced by changing the number of elastic bubbles.

[0013] The advantages and positive effects of the present invention are:

[0014] 1. In the present invention, the base with sealed elastic bubbles is installed below the spire. The high-frequency sound waves in the sound waves are absorbed by the gaps of the spire fiber cotton, and the low-frequency sound waves continue to pass through the sound-permeable holes on the base, causing each elastic bubble to vibrate, and generating high-frequency sound waves with wavelengths equivalent to the size of the elastic bubbles inside the base. Since the sound waves generated by the elastic bubbles are out of phase, the sound waves generated by the elastic bubbles are absorbed by the sound-absorbing fibers at the bottom inside the base. Therefore, the low-frequency sound waves entering the sound-permeable holes are absorbed, achieving the effect of absorbing low-frequency sound waves as a whole. This method of absorbing external noise in frequency bands realizes the sound absorption function of the sound absorption structure for low-frequency sound waves below 100 Hz without increasing the size.

[0015] 2. The elastic bubbles of the present invention can convert the energy of low-frequency sound waves into the energy of high-frequency sound waves, and the high-frequency sound waves generated by each sealed elastic bubble are out of phase. The high-frequency sound waves are absorbed by the sound-absorbing fibers at the bottom of the base and will not penetrate back through the sound-permeable holes, achieving the effect of absorbing low-frequency sound waves. The lower limit of the absorption frequency can be reduced without changing the size. For a general structure with a height of 1 m, the lower limit of the absorption frequency is about 150 Hz. After using the base of the present invention, the lower limit of the absorption frequency can be reduced to about 10 Hz.

[0016] 3. In the present invention, the lower limit of the absorption frequency can be changed by varying the size of the elastic bubbles. On the premise of keeping them from touching each other, the low-frequency absorption rate can be reduced by changing the number of elastic bubbles, that is, the more sealed elastic bubbles there are, the better the absorption effect on low frequencies. Description of the Drawings

[0017] Figure 1 is a schematic structural diagram of the present invention;

[0018] Among them, 1 - spire, 2 - sound-absorbing fiber, 3 - base, 4 - base cover plate, 5 - sound-permeable hole, 6 - elastic bubble. Detailed Embodiments

[0019] The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0020] A low-frequency sound absorption structure, as Figure 1 shown, includes a spire 1 and a base 3, and the spire 1 is installed on the base.

[0021] The spire 1 is formed by bonding sound-absorbing fibers 2 into a block-shaped ramp structure. The surface of the spire 1 is provided with dense sound-permeable gaps. The ramp structure can be: a pair of ramps and a pair of vertical plane structures, or a four-sided ramp structure, or a conical structure.

[0022] The base 3 is a regular frame structure in the shape of a square or a circle with a closed perimeter and top and an open bottom. A base cover plate 4 is provided on the top of the base 3. Dense sound-permeable holes 5 are formed on the surface of the base cover plate 4. Each sound-permeable hole 5 is short tubular. The bottom of the sound-permeable hole 5 is located inside the base 3. A sealed elastic bubble 6 is bonded to the lower end of the sound-permeable hole 5. A certain gap is left between each elastic bubble 6, and the gap is less than 6 mm. The elastic bubble 6 undergoes elastic deformation under the action of sound waves, and then sound waves with a wavelength equivalent to the size of the elastic bubble 6 are generated inside the base 3. Sound-absorbing fibers 2 are laid at the bottom of the base 3, and the sound-absorbing fibers 2 can absorb the sound waves emitted by the elastic bubbles 6.

[0023] In the present invention, by changing the size of the elastic bubbles 6, the lower limit of the sound absorption frequency can be changed. By changing the number of the elastic bubbles 6, the low-frequency sound absorption rate can be changed. When the number of the elastic bubbles 6 is larger, the sound absorption coefficient of the low-frequency sound is higher, and the lower limit of the combined sound absorption frequency is lower.

[0024] Based on the above low-frequency sound absorption structure, the present invention also proposes a sound absorption method for a low-frequency sound absorption structure. The method includes: when sound waves pass through the dense sound-permeable gaps provided on the surface of the spire, the high-frequency sound waves are absorbed, and the low-frequency sound waves pass through the sound-permeable holes on the base cover plate to cause each elastic bubble to vibrate, and high-frequency sound waves with a wavelength equivalent to the size of the bubbles are generated inside the base. The sound waves generated by the elastic bubbles are out of phase, and the sound waves generated by the elastic bubbles are absorbed by the sound-absorbing fibers at the bottom inside the base, so that the low-frequency sound waves entering the sound-permeable holes are absorbed.

[0025] The working principle of the low-frequency sound absorption structure of the present invention is:

[0026] When the sound wave penetrates through the pores of the fibrous material of the spire, the high-frequency sound wave energy is absorbed, causing the sound pressure to be attenuated. The height of the spire corresponds to half the wavelength of the sound wave at the lower limit of the sound absorption frequency. The unabsorbed low-frequency sound wave enters the dense sound-transmitting holes on the upper cover plate of the base, causing the sealed elastic vesicles at the lower end of the sound-transmitting holes to bulge and contract, and generating high-frequency sound waves by secondary radiation in the cavity. Since the diameter of the sealed elastic vesicles is less than 6 mm, the sound frequency generated by them is higher than 10 kHz. The sound waves generated by the elastic vesicles are absorbed by the sound-absorbing fibers at the bottom in the base, thereby achieving the absorption of sound waves with a half wavelength greater than the height of the spire. The spire and the base work together to achieve the broadband sound absorption function.

[0027] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes, but is not limited to, the embodiments described in the specific embodiments. Any other embodiments obtained by those skilled in the art according to the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims

1. A low-frequency sound absorption structure, comprising a spire and its base, and having dense sound-permeable slits on the surface of the spire, characterized in that: The base has a structure that is closed on its peripheral side and top and open at the bottom. A base cover plate is provided on the top of the base. Dense sound-transmitting holes are formed on the surface of the base cover plate. Each sound-transmitting hole is short tubular. The bottom of the sound-transmitting hole is located inside the base. An elastic small bubble is bonded at the lower end of the sound-transmitting hole. A certain gap is left between each elastic small bubble. Sound-absorbing fibers are laid at the bottom of the base; The gap left between the elastic small bubbles is less than 6 mm; The base is a regular frame structure that is square or circular, with its peripheral side and top closed and bottom open; The spire is a ramp-shaped structure formed by bonding sound-absorbing fibers into a block.

2. The low-frequency sound absorption structure according to claim 1, wherein: The ramp-shaped structure is a structure of a pair of ramps and a pair of vertical planes, or a structure of four-sided ramps, or a conical structure.

3. The low-frequency sound absorption structure according to claim 1, characterized in that: The spire and the base are installed together by bonding.

4. The sound absorption method of a low-frequency sound absorption structure according to any one of claims 1 to 3, characterized in that: It includes the following steps: When sound waves pass through the dense sound-transmitting slits provided on the surface of the spire, high-frequency sound waves are absorbed. The low-frequency sound waves pass through the sound-transmitting holes on the base cover plate, causing each elastic small bubble to vibrate, and generating high-frequency sound waves with a wavelength equivalent to the size of the small bubbles inside the base. The sound waves generated by the elastic small bubbles are out of phase, and the sound waves generated by the elastic small bubbles are absorbed by the sound-absorbing fibers at the bottom inside the base, so that the low-frequency sound waves entering the sound-transmitting holes are absorbed.

5. The sound absorption method of a low-frequency sound absorption structure according to claim 4, characterized in that: By changing the size of the elastic small bubbles, the lower limit of the sound absorption frequency is changed. By changing the number of elastic small bubbles, the low-frequency sound absorption rate is reduced.

Images