Constant topology acoustic enhancement sensor based on acoustic heterostructure and construction method thereof

Abstract

This invention discloses a constant topology acoustic enhancement sensor based on acoustic heterostructures and its construction method. The acoustic enhancement sensor includes two basic phonon crystal units with different bandgap widths. Each basic phonon crystal unit comprises 2N+1 rectangular waveguides connected sequentially, where N is a positive integer greater than or equal to 1. Each rectangular waveguide has the same width b. The total length of each basic phonon crystal unit is a constant value a, and it is mirror-symmetric about its central cross-section, with a varying cross-section along its length. The two basic phonon crystal units are spliced ​​end-to-end. When adjusting the frequency, the structural parameters of one basic phonon crystal unit are kept constant, while the length parameter of the rectangular waveguide in the middle of the other basic phonon crystal unit is adjusted while keeping the total length a of the basic phonon crystal units constant. This invention can achieve frequency shift of the interface state within the bandgap range, and the acoustic enhancement remains nearly constant during frequency changes.

Description

Technical Field

[0001] This invention relates to acoustic enhancement sensors, and more specifically to a constant topology acoustic enhancement sensor based on acoustic heterostructures and its construction method. Background Technology

[0002] In the field of acoustics, how to achieve constant sound intensity enhancement is a fundamental problem.

[0003] Traditional sound enhancement sensor models have a relatively complex structure. Once the structure is determined, its interface state frequency is fixed, which is not very flexible. If the frequency needs to be adjusted, multiple structural parameters need to be adjusted at the same time, which is complicated and cumbersome. Moreover, there is still the problem of unstable sound enhancement after adjustment. Summary of the Invention

[0004] Objectives of the invention: The first objective of this invention is to provide a constant topology acoustic enhancement sensor based on an acoustic heterostructure that is simple to adjust in frequency and whose acoustic enhancement remains nearly constant during frequency changes; the second objective of this invention is to provide a method for constructing the constant topology acoustic enhancement sensor.

[0005] Technical Solution: The constant topological acoustic enhancement sensor based on acoustic heterostructure of the present invention includes two basic phonon crystal units with different bandgap widths. Each basic phonon crystal unit includes 2N+1 rectangular waveguides connected in sequence, where N is a positive integer greater than or equal to 1, and each rectangular waveguide has the same width b. The total length of the basic phonon crystal unit is a constant value a, and it is mirror-symmetric about its central cross-section and has a varying cross-section along its length. The two basic phonon crystal units are spliced ​​end to end. When adjusting the frequency, the structural parameters of one basic phonon crystal unit are kept unchanged, while the length parameter of the rectangular waveguide in the middle of the other basic phonon crystal unit is adjusted while keeping the total length a of the basic phonon crystal unit unchanged.

[0006] In this invention, the number of rectangular waveguides in the basic phononic crystal unit is odd, such as three, five, or seven. Considering factors such as size, it is not advisable to exceed ten. Variations in the number of rectangular waveguides will affect the frequency range, but the technical effect remains consistent: all can achieve changes in the interface state frequency, and the magnitude of the acoustic enhancement remains almost constant during frequency changes.

[0007] Furthermore, the two basic phonon crystal units are spliced ​​together end-to-end.

[0008] Furthermore, N is set to 2, and the (length, width, height) of the five rectangular waveguides are (a1,b,h1), (a2,b,h2), (a3,b,h1), (a2,b,h2), and (a1,b,h1), respectively, where h1 ≠ h2; the total length a of the basic phonon crystal unit is 2a1 + 2a2 + a3; when adjusting the frequency, the structural parameters of one basic phonon crystal unit are kept unchanged, while the length parameter a3 of the middle rectangular waveguide of another basic phonon crystal unit is adjusted, and the total length a of the basic phonon crystal unit is kept unchanged.

[0009] Furthermore, a = 21cm, b = 4cm, h1 = 2cm, h2 = 4cm.

[0010] Furthermore, M extended phonon crystal units can be spliced ​​to the other end of any basic phonon crystal unit, where M is a positive integer greater than or equal to 1.

[0011] In this invention, after determining two basic phonon crystal units, extended phonon crystal units can be provided at the ends. However, when the number of extended phonon crystal units is large, the length of the sound enhancement sensor will increase, leading to a decrease in the sound enhancement effect. Therefore, the number of extended phonon crystal units should not be too large, and the number of extended phonon crystal units at the outer end of any one basic phonon crystal unit should not exceed ten.

[0012] Furthermore, the extended phononic crystal unit has the same structure as the basic phononic crystal unit, and the length parameters of each rectangular waveguide can be the same as or different from those of the basic phononic crystal unit.

[0013] Once the basic phononic crystal unit structure is determined, the acoustic enhancement sensor can achieve the technical effect of changing the interface state frequency and maintaining a nearly constant acoustic enhancement during the frequency change. The role of setting up extended phononic crystal units is only to adjust the range of frequency change. Therefore, it is only necessary to ensure that the extended phononic crystal unit has the same structure as the basic phononic crystal unit and that the width and height of the corresponding rectangular waveguide are consistent. The length parameter of the rectangular waveguide can be the same or different, and there are no special requirements.

[0014] The method for constructing a constant topological acoustic enhancement sensor according to the present invention includes:

[0015] Keeping the total length 'a' of the basic phonon crystal unit constant, a set of different structural parameters are constructed by changing the length parameter of the intermediate rectangular waveguide.

[0016] Calculate the band diagram of the basic phononic crystal unit and the Zak phase of each band under the set of different structural parameters. Arbitrarily select a pair of structural parameters with different band gap widths and topological phase transitions, and construct two basic phononic crystal units using the selected pair of structural parameters.

[0017] Two basic phonon crystal units are spliced ​​end-to-end to obtain the constant topological acoustic enhancement sensor described above.

[0018] Interface state frequency adjustment is achieved by keeping the structural parameters of one basic phononic crystal unit unchanged, adjusting the length parameter of the middle rectangular waveguide of another basic phononic crystal unit, and keeping the total length 'a' of the basic phononic crystal unit unchanged, thereby realizing constant acoustic enhancement during the shift of the interface state frequency within the bandgap range and frequency change.

[0019] Furthermore, the Zak phase is calculated using the following formula:

[0020]

[0021] in, It is the Zak phase of the nth band, k represents the wave vector, i represents the imaginary unit, unit cell represents a unit cell, ρ is the mass density of the acoustic system, c is the speed of sound in air, and u n，k (x) is a periodic Bloch eigenfunction with wavenumber k. Indicates the relationship between u n，k (x) take the conjugate;

[0022] The sound pressure field is p(x) = u(x)exp(ikx).

[0023] Furthermore, the transformation of topological properties is characterized by band reversal.

[0024] Furthermore, the sound pressure enhancement ratio is 10. 4 Magnitude.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0026] This invention overcomes the problem of traditional acoustic enhancement sensors where the interface states occur at a fixed frequency. By changing only one structural parameter in the basic phonon crystal unit, modulation of the interface state frequency within the bandgap frequency band can be achieved. The interface state frequency shift is accompanied by a significant increase in sound intensity, and this sound enhancement remains nearly constant during frequency changes, exhibiting strong robustness. This invention achieves high and stable local intensity enhancement within the bandgap frequency, which has broad application prospects for many important scenarios, such as non-destructive acoustic detection and biomedical imaging. Attached Figure Description

[0027] Figure 1 (a) is a schematic diagram of a constant topological acoustic enhancement sensor based on an acoustic heterostructure provided in an embodiment of this application; Figure 1 (b) in the figure is a schematic diagram of different band gap widths of heterostructures in the embodiments of this application;

[0028] Figure 2 In the example, (a) represents the phononic crystal band and Zak phase in the acoustic enhancement sensor of this application. Figure 2 (b) is a schematic diagram of the band inversion topological transition in an embodiment of this application;

[0029] Figure 3 This refers to the sound pressure enhancement ratio at the interface based on the topological acoustic heterostructure in the embodiments of this application;

[0030] Figure 4 This is a schematic diagram of multi-frequency and nearly constant sound enhancement implemented in the embodiments of this application. Detailed Implementation

[0031] The invention will now be further described with reference to the accompanying drawings.

[0032] This application uses an example of an acoustic enhancement sensor constructed from two basic phonon crystal units with five rectangular waveguides to illustrate the present invention.

[0033] like Figure 1 As shown in (a), the constant topological acoustic enhancement sensor based on an acoustic heterostructure includes two basic phonon crystal units with different bandgap widths. Each basic phonon crystal unit comprises five rectangular waveguides connected in sequence. Each rectangular waveguide is mirror-symmetric about its central cross-section, and the (length, width, height) of the five rectangular waveguides are (a1, b, h1), (a2, b, h2), (a3, b, h1), (a2, b, h2), and (a1, b, h1), respectively, where h1 ≠ h2. The total length of the basic phonon crystal unit is a constant value 'a'. The basic phonon crystal unit is mirror-symmetric about its central cross-section and has a cross-section that varies along its length. Two basic phonon crystal units are spliced ​​end-to-end to form the constant topological acoustic enhancement sensor.

[0034] When adjusting the frequency, keep the structural parameters of one basic phonon crystal unit unchanged, adjust the length parameter a3 of the rectangular waveguide in the middle of another basic phonon crystal unit, and keep the total length a of the basic phonon crystal unit unchanged.

[0035] In this embodiment, a = 2a1 + 2a2 + a3 = 21cm, b = 4cm, h1 = 2cm, h2 = 4cm.

[0036] The method for constructing a constant topological acoustic enhancement sensor as described in this application includes the following steps:

[0037] (1) Keep the total length a of the basic phonon crystal unit constant, and change the length parameter a3 of the intermediate rectangular waveguide to construct a set of different structural parameters;

[0038] The basic phonon crystal unit cell has different bandgap widths under different structural parameter configurations, such as Figure 1 As shown in (b) in the figure, these are the characteristics of forming a heterogeneous structure.

[0039] (2) Figure 2 As shown in (a), the band structure diagrams of the basic phonon crystal unit and the Zak phase of each band are calculated under the set of different structural parameters. A pair of structural parameters with different band gap widths and a topological phase transition are arbitrarily selected, for example... Figure 2 In (b) above, S1 and S4 correspond to a3 of 4 cm and 12 cm, respectively. The transformation of topological properties is... Figure 2 The band reversal shown in (b) is a characteristic. The selected S1 and S4 are merely exemplary; for example, a3 could also be selected as 3cm and 11cm.

[0040] The Zak phase is calculated using the following formula:

[0041]

[0042] in, It is the Zak phase of the nth band, k represents the wave vector, i represents the imaginary unit, unit cell represents a unit cell, ρ is the mass density of the acoustic system, c is the speed of sound in air, and u n，k (x) is a periodic Bloch eigenfunction with wavenumber k. Indicates the relationship between u n，k (x) take the conjugate;

[0043] The sound pressure field is p(x) = u(x)exp(ikx).

[0044] An acoustic enhancement sensor based on an acoustic heterostructure is constructed using two basic phonon crystal units with different bandgap widths corresponding to parameters S1 and S4, such as... Figure 1 As shown in (a) in the figure.

[0045] Due to the topological transition from trivial to nontrivial, topological interface states exist at the interface and are accompanied by significant acoustic enhancement, such as... Figure 3 As shown, the sound pressure enhancement ratio is as high as 10. 4 The magnitude of the acoustic enhancement at the interface occurs at a specific frequency of 2360 Hz, which is within the bandgap band.

[0046] (3) Interface state frequency adjustment: The structural parameters of the basic phonon crystal unit on one side of the interface are kept constant. The length parameter a3 of the middle rectangular waveguide of the basic phonon crystal unit on the other side is adjusted while keeping the total length a of the basic phonon crystal unit constant. This achieves the shift of the interface state frequency within the bandgap range. Figure 4As shown, the sound enhancement remains almost constant during frequency changes, demonstrating strong robustness.

Claims

1. A constant topological acoustic enhancement sensor based on an acoustic heterostructure, characterized in that, It includes two basic phononic crystal units with different bandgap widths. Each basic phononic crystal unit consists of 2N+1 rectangular waveguides connected in sequence, where N is a positive integer greater than or equal to 1. Each rectangular waveguide has the same width b. The total length of the basic phononic crystal unit is a constant value a. It is mirror-symmetric about its central cross-section and has a varying cross-section along its length. The two basic phononic crystal units are spliced ​​end to end. When adjusting the frequency, the structural parameters of one basic phononic crystal unit are kept constant, while the length parameter of the rectangular waveguide in the middle of the other basic phononic crystal unit is adjusted while keeping the total length a of the basic phononic crystal unit constant.

2. The constant topological acoustic enhancement sensor according to claim 1, characterized in that, Two basic phonon crystal units are spliced ​​together end-to-end.

3. The constant topological acoustic enhancement sensor according to claim 1, characterized in that, N is set to 2. The (length, width, height) of the five rectangular waveguides are (a1,b,h1), (a2,b,h2), (a3,b,h1), (a2,b,h2), and (a1,b,h1), respectively, where h1 ≠ h2. The total length of the basic phonon crystal unit is a = 2a1 + 2a2 + a3. When adjusting the frequency, the structural parameters of one basic phonon crystal unit are kept constant, while the length parameter a3 of the middle rectangular waveguide of another basic phonon crystal unit is adjusted, and the total length a of the basic phonon crystal unit is kept constant.

4. The constant topological acoustic enhancement sensor according to claim 3, characterized in that, a=21cm, b=4cm, h1=2cm, h2=4cm.

5. The constant topological acoustic enhancement sensor according to any one of claims 1 to 4, characterized in that, M extended phonon crystal units can be spliced ​​to the other end of any basic phonon crystal unit, where M is a positive integer greater than or equal to 1.

6. The constant topological acoustic enhancement sensor according to claim 5, characterized in that, The extended phononic crystal unit has the same structure as the basic phononic crystal unit, and the length parameters of each rectangular waveguide can be the same as or different from those of the basic phononic crystal unit.

7. The method for constructing the constant topological acoustic enhancement sensor according to claim 1, characterized in that, include: Keeping the total length 'a' of the basic phonon crystal unit constant, a set of different structural parameters are constructed by changing the length parameter of the intermediate rectangular waveguide. Calculate the band diagram of the basic phononic crystal unit and the Zak phase of each band under the set of different structural parameters. Arbitrarily select a pair of structural parameters with different band gap widths and topological phase transitions, and construct two basic phononic crystal units using the selected pair of structural parameters. Two basic phonon crystal units are spliced ​​end-to-end to obtain the constant topological acoustic enhancement sensor described above. Interface state frequency adjustment is achieved by keeping the structural parameters of one basic phononic crystal unit unchanged, adjusting the length parameter of the middle rectangular waveguide of another basic phononic crystal unit, and keeping the total length 'a' of the basic phononic crystal unit unchanged, thereby realizing constant acoustic enhancement during the shift of the interface state frequency within the bandgap range and frequency change.

8. The method for constructing the constant topological acoustic enhancement sensor according to claim 7, characterized in that, The Zak phase is calculated using the following formula: in, It is the Zak phase of the nth band, where k represents the wave vector. The imaginary unit is represented by "unitcell". It is the mass density of the acoustic system. It is the speed of sound in the air. These are periodic Bloch eigenfunctions with wavenumber k. Indicates to Take conjugate.

9. The method for constructing the constant topological acoustic enhancement sensor according to claim 7, characterized in that, The transition of topological phase is characterized by band reversal.

10. The method for constructing the constant topological acoustic enhancement sensor according to claim 7, characterized in that, sound pressure enhancement ratio 10 4 Magnitude.

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