A helmholtz resonant sound absorption structure with an impedance post

Abstract

The utility model provides a kind of helmholtz resonance sound absorption structure with impedance column, including the shell body with empty cavity inside and the impedance column arranged in shell body, the top surface of the shell body is opened with air inlet hole, the end surface of the impedance column blocks the air inlet hole, and the material of the impedance column is porous sound absorption material. It can greatly increase the sound absorption bandwidth of traditional helmholtz resonance cavity sound absorption structure.

Description

Technical Field

[0001] This invention belongs to the field of acoustic metamaterials technology, specifically relating to a Helmholtz resonant sound-absorbing structure with an impedance column. Background Technology

[0002] The Helmholtz resonator is a commonly used acoustic resonant structure consisting of a neck and a cavity, capable of producing sound absorption at specific frequencies. This structure achieves energy absorption at specific frequencies through the interaction between the vibration of the air column in the neck and the vibration of the air within the cavity. While traditional Helmholtz resonator structures are effective in specific applications, their absorption bandwidth is relatively narrow, limiting their practical application to specific frequencies and restricting their widespread use. Summary of the Invention

[0003] To solve the above-mentioned technical problems, this utility model provides a Helmholtz resonant sound-absorbing structure with an impedance column, which can significantly increase the sound absorption bandwidth of the traditional Helmholtz resonant cavity sound-absorbing structure.

[0004] To achieve the objective of this utility model, the technical solution adopted by this utility model is as follows: A Helmholtz resonant sound-absorbing structure with an impedance column includes an outer shell with an internal cavity and an impedance column disposed within the outer shell. The top surface of the outer shell has an air inlet, and the end face of the impedance column blocks the air inlet. The impedance column is made of a porous sound-absorbing material.

[0005] The porous sound-absorbing material of this invention is installed inside the outer shell via a support frame.

[0006] Preferably, the support frame is composed of rigid wires, which support the columns from the inside or outside of the porous sound-absorbing material and are connected to the outer shell. The support frame composed of rigid wires does not impede the sound-absorbing material's resistance.

[0007] The impedance column of this invention has the same length as the cavity, resulting in superior sound absorption performance and bandwidth.

[0008] The end face of the impedance column of this invention just blocks the air inlet, resulting in optimal sound absorption performance.

[0009] The beneficial effects of this invention are as follows: The Helmholtz resonant sound-absorbing structure of this invention is simple. Sound waves propagate and diffuse within the porous material column, extending the effect of sound waves from the area of ​​a small aperture on the cavity to the effect of a cylindrical surface. The impedance column alters the end radiation acoustic impedance correction value, increasing the radiation impedance at the end of the aperture, thereby improving the sound absorption quality of the aperture and increasing the sound absorption bandwidth, which is superior to the traditional Helmholtz resonant cavity sound-absorbing structure. Attached Figure Description

[0010] Figure 1 This is an external view of the Helmholtz resonant sound-absorbing structure of this utility model.

[0011] Figure 2 This is a schematic diagram of the internal cavity of the Helmholtz resonant sound-absorbing structure of this utility model.

[0012] Figure 3 This is a schematic diagram of a cavity when the length of the impedance column is the same as the height of the cavity.

[0013] Figure 4 This is a cross-sectional view of the sound-absorbing superstructure in Example 4.

[0014] Figure 5 This is a cross-sectional view of the sound-absorbing superstructure in Example 5.

[0015] Figure 6 This paper compares the sound absorption performance of the Helmholtz resonant sound-absorbing structure of this invention with that of a conventional structure.

[0016] Figure 7 A comparison of the sound absorption performance of Helmholtz resonant structures with different impedance column lengths.

[0017] The markings in the diagram are: 1. Outer shell; 2. Air inlet; 3. Impedance column; 4. Support frame; 41. Rigid wire. Detailed Implementation

[0018] To more clearly and in detail illustrate the objective technical solution of this utility model, the present utility model will be further described below through relevant embodiments. The following embodiments are merely illustrative of the implementation methods of this utility model and do not limit the scope of protection of this utility model. Example 1

[0019] like Figure 1 and Figure 2 As shown, a Helmholtz resonant sound-absorbing structure with an impedance column includes an outer shell 1 with an internal cavity and an impedance column 3 disposed inside the outer shell 1. The top surface of the outer shell 1 has an air inlet 2, and the end face of the impedance column 3 blocks the air inlet 2. The material of the impedance column 3 is a porous sound-absorbing material.

[0020] In a traditional Helmholtz resonator, sound waves propagate through a small aperture and then enter the air cavity. In this invention, the sound waves propagate and diffuse within a porous material column, extending the effect of the sound waves from the area of ​​a small aperture on the air cavity to the effect of a cylindrical surface. The sound waves no longer enter the air cavity through the aperture, but rather through an impedance column composed of porous material. The presence of this impedance column alters the end-radiated acoustic impedance correction value.

[0021] The traditional formula for calculating the correction value of the radiation acoustic impedance at the end of a Helmholtz resonant cavity is Rr=πρc / (2λ2), where ρc is the characteristic impedance of air and λ is the wavelength equivalent to the vibration frequency. This invention uses the characteristic impedance value of porous material instead of the characteristic impedance of air. Under the same cavity parameters, the presence of the impedance column improves the sound absorption quality of the small hole by increasing the radiation impedance at the end of the air inlet, thus significantly increasing the sound absorption bandwidth of the Helmholtz resonant cavity.

[0022] The shape of the impedance column can be a cylinder, cuboid, or an irregular shape such as a triangular or hexagonal column, as long as it can block the air inlet.

[0023] The air inlet of the Helmholtz resonator was set to 4mm, 6mm and 8mm respectively. Under the same Helmholtz resonator structural parameters, three sets of simulation results were compared between the Helmholtz resonator with impedance column in this embodiment and the conventional resonator.

[0024] Depend on Figure 6 As can be seen, when the aperture is 8mm, the sound absorption coefficient of the Helmholtz resonator without impedance pillars is less than 0.1, showing no sound absorption effect. The sound absorption coefficient of the resonator with impedance pillars is above 0.9, and the frequency range with a coefficient above 0.5 is from 250Hz to 800Hz, with a bandwidth approaching two octaves. The bandwidth of a conventional Helmholtz resonator is less than 1 / 6 of an octave, meaning the sound absorption bandwidth of the Helmholtz resonator with impedance pillars is more than 12 times that of a conventional resonator structure. When the aperture is 4mm and 6mm, the sound absorption coefficient of the Helmholtz resonator with impedance pillars is still significantly better than that of a conventional Helmholtz resonator, and the bandwidth also reaches two octaves.

[0025] The porous sound-absorbing material used in this embodiment is sound-absorbing cotton. Since the characteristic impedance values ​​of porous materials are significantly higher than those of air, other porous materials can also be used to obtain a sound-absorbing superstructure with better sound absorption performance. Example 2

[0026] This embodiment is based on embodiment 1: The impedance column lengths were taken as follows: L = 1mm (minimum) and L = 50mm (maximum, equal to the height of the cavity, see...). Figure 3 A simulation comparison was performed on two Helmholtz resonator structures with different impedance column lengths, see [link / reference]. Figure 7 It is evident that both can achieve a sound absorption bandwidth of two octaves in the low-frequency range. When the impedance column length is the same as the cavity height, both the sound absorption performance and bandwidth are superior. Example 3

[0027] This embodiment is based on embodiment 1: like Figure 4As shown, the impedance column 3 is installed inside the outer shell 1 via a support frame 4. The support frame 4 is composed of rigid wires 41, which support the column from the outside of the porous sound-absorbing material and are connected to the outer shell 1. The connection between the rigid wires 41 and the inner wall of the outer shell 1 can be by snap-fit ​​or riveting. Example 4

[0028] This embodiment is based on embodiment 1: like Figure 5 As shown, the impedance column 3 is installed inside the outer shell 1 via a support frame 4. The support frame 4 is composed of rigid wires 41, which support the column from inside the porous sound-absorbing material and are connected to the outer shell 1. The connection between the rigid wires 41 and the inner wall of the outer shell 1 can be by snap-fit ​​or riveting. Example 5

[0029] This embodiment is based on embodiment 1: The end face of the impedance column 3 just blocks the air inlet 2.

[0030] The connection methods not mentioned in this utility model are conventional connection methods such as threaded connection, snap-fit ​​connection, riveting, welding, bonding and integral molding.

[0031] The embodiments described above merely illustrate specific implementations of this utility model, and while the descriptions are detailed, they should not be construed as limiting the scope of this utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these modifications and improvements all fall within the protection scope of this utility model.

Claims

1. A Helmholtz resonant sound-absorbing structure with an impedance column, characterized in that: It includes an outer shell with an internal cavity and an impedance column disposed within the outer shell. The top surface of the outer shell has an air inlet, and the end face of the impedance column blocks the air inlet. The impedance column is made of porous sound-absorbing material.

2. The Helmholtz resonant sound-absorbing structure with impedance column according to claim 1, characterized in that: The porous sound-absorbing material is installed inside the outer shell via a support frame.

3. The Helmholtz resonant sound-absorbing structure with impedance pillar according to claim 2, characterized in that: The support frame is composed of rigid wires, which support columns from the inside or outside of the porous sound-absorbing material and are connected to the outer shell.

4. The Helmholtz resonant sound-absorbing structure with impedance column according to claim 1, characterized in that: The length of the impedance column is the same as the height of the cavity.

5. The Helmholtz resonant sound-absorbing structure with impedance column according to claim 1, characterized in that: The end face of the impedance column just blocks the air inlet.

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