An ultra-broadband transmission acoustic metamaterial

Abstract

The present invention discloses an ultra-wideband transmission type acoustic metamaterial, which is composed of a number of rigid boundary units connected side by side. Each unit includes a square straight waveguide tube, and a number of pairs of straight baffle groups arranged parallel and at equal intervals along the central axis of the square straight waveguide tube. Sound waves enter from one end of the ultra-wideband transmission type metamaterial structure and are transmitted out from the other end. By adjusting the distance between the two straight baffles in each pair of straight baffle groups in different rigid boundary units, the equivalent phase of the transmitted sound wave can be continuously adjusted within a range of 360 degrees. The ultra-wideband transmission type acoustic metamaterial of the present invention has a simple structure and high sound wave transmission efficiency due to its non-resonant structural design, and can realize arbitrary manipulation of ultra-wideband transmission sound waves. Since the operating frequency band of the ultra-wideband transmission type acoustic metamaterial of the present invention covers most of the audible range, it can greatly optimize the problems of complex structure and narrow operating frequency band faced by existing traditional acoustic metamaterials.

Description

Technical Field

[0001] The present invention belongs to the field of acoustic materials, and in particular relates to an ultra-wideband transmission type acoustic metamaterial. Background Art

[0002] Acoustic metamaterials possess properties not found in traditional acoustic materials, allowing for arbitrary manipulation of sound waves. They are widely used in fields such as acoustic particle suspension, acoustic display devices, medical ultrasound testing, and ultrasonic surgery. In his paper "Dispersion-free Manipulation of Reflected Acoustic Wavefronts by Subwavelength Corrugated Surfaces," Zhu Yifan employed a reflective straight tube structure to achieve arbitrary manipulation of broadband reflected sound waves. However, because the metamaterial structure proposed by Zhu Yifan is reflective, the incident sound field will alias with the reflected sound field, interfering with the reflected sound field, hindering practical applications. In his paper "Acoustic Passive Phased Array Based on Metascreen," Li Yong employed a straight waveguide connected to four side-branch Helmholtz resonant cavities to achieve manipulation of single-frequency sound waves. However, because the structure proposed by Li Yong is resonant, the operating frequency band of the sound waves is extremely narrow, making it unsuitable for practical applications. Summary of the Invention

[0003] To overcome the shortcomings of the existing technology, the present invention proposes an ultra-wideband transmission-type acoustic metamaterial, which solves the problem of aliasing of the incident sound field and the reflected sound field in existing reflective metamaterials, and also solves the problem of the narrow operating frequency band of existing transmission metamaterials. It can realize arbitrary manipulation of ultra-wideband transmission sound waves and can solve the problem of complex structure faced by existing traditional acoustic metamaterials.

[0004] The technical solution for realizing the present invention is: an ultra-wideband transmission type acoustic metamaterial, which is composed of a number of rigid boundary units of length L connected side by side. Each rigid boundary unit includes a square straight waveguide tube, and a number of pairs of straight baffle groups fixed in parallel and at equal intervals in the square straight waveguide tube along the central axis direction of the square straight waveguide tube, and two pairs of straight baffle groups are fixed at the two ends of the square straight waveguide tube. Each pair of straight baffle groups is composed of two rectangular straight baffles arranged side by side at intervals. Sound waves enter from one end of the ultra-wideband transmission type metamaterial structure, interact with the structure, and are transmitted out from the other end. By adjusting the distance between the two straight baffles in each pair of straight baffle groups in different rigid boundary units, the equivalent phase of the transmitted sound wave can be continuously adjusted within a range of 360 degrees.

[0005] Preferably, the straight waveguide tube is a square waveguide tube.

[0006] Preferably, the straight baffles are parallel and rectangular straight baffles fixed at equal intervals.

[0007] Preferably, the three sides of each straight baffle are fixedly connected to the three inner walls of the square straight waveguide tube, and the distance between the two straight baffles in the same pair of straight baffles, that is, the opening size is d.

[0008] Preferably, the thickness of the square straight waveguide and the straight baffle therein in the same rigid boundary unit is equal to w, the height D of the rigid boundary unit is at least 7w, and D should be smaller than the operating wavelength λ.

[0009] Compared with the prior art, the present invention has the following significant advantages: (1) The ultra-wideband transmission-type acoustic metamaterial of the present invention is composed of a number of rigid boundary units connected side by side, and the effective working frequency band can cover 3000 Hz to 17000 Hz.

[0010] (2) By adjusting the distance between the two straight baffles in each pair of straight baffles in different rigid boundary units, the equivalent phase of the transmitted sound wave can be continuously adjusted within a 360-degree range.

[0011] (3) The present invention adopts a non-resonant structural design with a simple structure and high sound wave transmission efficiency, which can realize arbitrary control of ultra-wideband transmitted sound waves, thereby solving the problems of complex structure and narrow working frequency band faced by existing traditional acoustic metamaterials. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the ultra-wideband transmission-type acoustic metamaterial structural unit of the present invention.

[0013] Figure 2 Schematic diagram of the transmission phase and transmittance of the ultra-wideband transmission acoustic metamaterial of the present invention.

[0014] Figure 3 Schematic diagram of phase distribution and structural parameter distribution of Example 1 of the present invention.

[0015] Figure 4 This is a schematic diagram of Example 1 of the present invention.

[0016] Figure 5 Schematic diagram of phase distribution and structural parameter distribution of Example 2 of the present invention.

[0017] Figure 6 This is a schematic diagram of Example 2 of the present invention. DETAILED DESCRIPTION

[0018] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In the present invention, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can refer to fixed connection, detachable connection, or integration; "connection" can refer to mechanical connection or electrical connection. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0020] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in this field can implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0021] The following will further introduce the specific implementation methods, as well as the technical difficulties and inventive points of this invention in combination with this design example.

[0022] like Figure 1 As shown, the ultra-wideband transmission type acoustic metamaterial described in the present invention is composed of a number of rigid boundary units with a length of L connected side by side. The rigid boundary unit includes a square straight waveguide tube, and a number of pairs of straight baffle groups fixed in parallel and at equal intervals in the square straight waveguide tube along the central axis direction of the square straight waveguide tube, and two pairs of straight baffle groups are fixed at both ends of the square straight waveguide tube. Each pair of straight baffle groups is composed of two rectangular straight baffles arranged side by side at intervals. Sound waves enter from one end of the ultra-wideband transmission type metamaterial, interact with the rigid boundary unit, and are transmitted out from the other end. As shown Figure 2 As shown, by adjusting the distance between the two straight baffles in each pair of straight baffles in different rigid boundary units, the equivalent phase of the transmitted sound wave can be continuously adjusted within a range of 360 degrees, and the effective working frequency band can cover 3000 Hz to 17000 Hz.

[0023] The ultra-wideband transmission acoustic metamaterial of the present invention utilizes a non-resonant structural design, resulting in a simple structure and high acoustic wave transmission efficiency, enabling arbitrary manipulation of ultra-wideband transmitted sound waves. Because its operating frequency band covers the vast majority of the audible range, it significantly mitigates the complex structures and narrow operating frequency bands faced by existing conventional acoustic metamaterials.

[0024] In the present invention, a required phase distribution, ie, a target, is firstly provided, and then the required phase is discretized, with each discrete phase point corresponding to a rigid boundary unit of an ultra-wideband transmission-type acoustic metamaterial with different geometric parameters.

[0025] Example 1

[0026] By following Figure 2The phase distribution corresponding to the frequency of 5715 Hz shown in the figure is used to design the ultra-wideband transmission type acoustic metamaterial. The length L of each rigid boundary unit is 50 mm, the width D is 10 mm, and the wall thickness is 0.5 mm. Figure 3 As shown, the centers of 100 rigid boundary elements with different opening sizes d are arranged in the y direction according to the corresponding phase distribution. Figure 4 The numerical simulation results of three frequency sound waves of 4400 Hz, 5700 Hz and 9700 Hz are shown in Figure 2. Figure 4 It can be seen from the figure that the ultra-wideband transmission-type acoustic metamaterial has a wide operating frequency band.

[0027] Example 2

[0028] By following Figure 2 The phase distribution corresponding to the frequency of 5715 Hz shown in the figure is used to design the ultra-wideband transmission type acoustic metamaterial. The length L of the rigid boundary unit is 50 mm, the width D is 10 mm, and the wall thickness is 0.5 mm. Figure 5 As shown, the centers of 100 rigid boundary elements with different opening sizes d are arranged in the y direction according to the corresponding phase distribution. Figure 6 The numerical simulation results of three frequency sound waves of 3800 Hz, 5800 Hz and 9800 Hz are shown in Figure 2. Figure 6 It can be seen that the ultra-wideband transmission-type acoustic metamaterial can realize arbitrary sound wave manipulation.

Claims

1. An ultra-wideband transmission acoustic metamaterial, characterized by: The invention comprises a plurality of rigid boundary units of length L arranged side by side, wherein the rigid boundary units include a square straight waveguide and a plurality of pairs of straight baffles fixed in parallel and at equal intervals within the square straight waveguide along the central axis of the square straight waveguide, with two pairs of straight baffles fixed at both ends of the square straight waveguide, each pair of straight baffles consisting of two rectangular straight baffles arranged side by side at intervals. The sound velocity and density of the ultra-wideband transmission-type acoustic metamaterial are much greater than the sound velocity and density of the background medium. The distance between the two straight baffles in each pair of straight baffles in the same rigid boundary unit is equal. By adjusting the distance between the two straight baffles in each pair of straight baffles in different rigid boundary units, the equivalent phase of the transmitted sound wave can be continuously adjusted within a 360-degree range.

2. The ultra-wideband transmission acoustic metamaterial according to claim 1, characterized in that: The three sides of each straight baffle are fixedly connected to the three inner walls of the square straight waveguide, and the distance between the two straight baffles in the same pair of straight baffles, that is, the opening size is d.

3. The ultra-wideband transmission acoustic metamaterial according to claim 1, characterized in that: The thickness of the square straight waveguide and the straight baffle in the same rigid boundary unit is equal to w, the height D of the rigid boundary unit is at least 7w, and D should be smaller than the working wavelength λ.

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