An energy trapping structure coupling acoustic metamaterials and helmholtz resonator and a detection method thereof

Abstract

The application provides a piezoelectric energy harvesting structure coupling a point defect acoustic metamaterial and a Helmholtz resonator and a detection method thereof, and belongs to the technical field of vibration energy harvesting. The structure comprises: a Helmholtz resonator, which is a cylindrical cavity structure, and the bottom and the neck are both provided with openings for amplifying the incident sound pressure at the resonance frequency; a point defect acoustic metamaterial, which is arranged at the bottom opening of the Helmholtz resonator and is composed of a substrate plate periodically arranged with stepped cross-section resonant columns, and the resonant columns are removed from the center to form a defect area for focusing sound energy on the defect area; and a piezoelectric transducer, which is embedded in the defect center area for converting the focused sound energy into electrical energy. Through the synergistic resonance effect between the sound pressure amplification of the Helmholtz resonator and the sound energy focusing of the point defect acoustic metamaterial, the application significantly improves the capture and conversion efficiency of low-frequency sound energy, and is suitable for the field of noise energy recovery of aircraft, etc.

Description

Technical Field

[0001] This invention relates to the field of vibration energy harvesting technology, specifically to an energy harvesting structure and detection method that couples an acoustic metamaterial with a Helmholtz resonator, which is particularly applicable to fields such as noise energy recovery from aircraft, vibration energy harvesting from industrial equipment, and power supply for low-power electronic devices. Background Technology

[0002] Acoustic metamaterials are artificially designed periodic composite material structures that exhibit extraordinary acoustic wave manipulation capabilities in the subwavelength band, such as sound absorption, negative refraction, and wave focusing, which are impossible for natural materials. When point defects are introduced into the acoustic metamaterial, a defect band with a group velocity approaching zero is formed within its bandgap frequency range. This causes the acoustic wave energy to be highly localized at the defect location, thus forming a high-intensity acoustic wave energy focusing region. Subsequently, piezoelectric materials are embedded into the defect region of the acoustic metamaterial, and the mechanical strain energy generated by the focused acoustic waves is converted into electrical energy through the piezoelectric effect.

[0003] In the aviation field, domestically produced large aircraft continuously generate noise during service from turbine engines, lift-enhancing devices, and the operation of mechanical components. This acoustic energy has not been effectively utilized. However, existing piezoelectric energy harvesting devices based on acoustic metamaterials generally suffer from the following technical shortcomings:

[0004] (1) Poor response to low-frequency sound waves. Most existing energy trapping structures operate in the mid-to-high frequency range, making it difficult to effectively capture the low-frequency noise energy generated by the operation of aircraft turbine engines, lift-enhancing devices, and mechanical components. Low-frequency sound waves have long wavelengths, and traditionally, larger sizes are required to achieve effective control, limiting their application in space-constrained scenarios.

[0005] (2) Low acoustic energy focusing density. The energy-harvesting structure using point-defect acoustic metamaterials relies solely on the localization effect of acoustic waves in the defect state for energy accumulation. It lacks a pre-amplification mechanism, resulting in limited acoustic energy density in the defect area and low energy output that the piezoelectric transducer can convert.

[0006] (3) Low energy conversion efficiency. In the existing technology, the acoustic energy capture and electrical energy conversion links are relatively independent and lack system-level collaborative optimization design. The energy loss is large in the multi-stage conversion process of acoustic energy to mechanical energy to electrical energy, and the overall energy capture efficiency is difficult to meet the actual engineering needs.

[0007] (4) Limited directional adaptability. Some existing acoustic metamaterial energy harvesting devices can only capture sound waves incident from a specific direction. Their energy harvesting ability is significantly reduced in multi-directional sound source environments, making them difficult to adapt to complex sound field environments such as aircraft. Summary of the Invention

[0008] In view of this, embodiments of the present invention provide an energy-harvesting structure and detection method for coupling acoustic metamaterials and Helmholtz resonators, aiming to solve the technical problems of poor low-frequency sound wave response, insufficient sound energy focusing density, and low energy conversion efficiency in the prior art. The present invention significantly improves low-frequency sound energy capture and piezoelectric conversion efficiency through the synergistic effect of the sound energy focusing effect of point-defect acoustic metamaterials and the sound pressure amplification characteristics of the Helmholtz resonator, thereby providing an effective solution for noise energy recovery in aircraft.

[0009] This application provides the following technical solution: an energy-harvesting structure coupling an acoustic metamaterial and a Helmholtz resonator, comprising: A Helmholtz resonant cavity includes a cylindrical cavity and a cavity neck communicating with the cavity. The bottom of the cavity and the surface of the cavity neck are provided with openings, and the opening at the bottom of the cavity is opposite to the opening at the cavity neck, so that the sound wave enters from the cavity neck and then passes through the cavity to amplify the sound pressure of the incident sound wave at the resonant frequency. A point-defect acoustic metamaterial is disposed at the opening at the bottom of the cavity, comprising a substrate plate and a plurality of resonant units arranged in a periodic array on the substrate plate. A point-defect region is disposed at the center of the plurality of resonant units. The defect region is formed by removing at least one resonant unit. The point-defect acoustic metamaterial is used to concentrate acoustic energy to the defect region at the defect band frequency. A piezoelectric transducer is fixed at the center of the defect region. The vibration direction of the piezoelectric transducer is perpendicular to the propagation direction of the sound wave in the acoustic metamaterial of the point defect. It is used to convert the accumulated sound energy into vibration energy through an external circuit and output electrical energy through the piezoelectric effect. The resonant frequency of the Helmholtz resonant cavity matches the defect band frequency of the point defect acoustic metamaterial to form a synergistic resonance effect, which causes the sound pressure amplified by the Helmholtz resonant cavity to form sound energy focusing enhancement in the defect region.

[0010] According to one embodiment of this application, the resonant unit is a stepped cross-section column, which is composed of a large-diameter section and a small-diameter section coaxially connected. The large-diameter section is located on the side away from the base plate, and the small-diameter section is located on the side close to the base plate and is fixedly connected to the base plate.

[0011] According to one embodiment of this application, the external circuit is a closed loop formed by connecting the upper and lower electrodes of the piezoelectric transducer to an external load via wires.

[0012] According to one embodiment of this application, the Helmholtz resonant cavity is made of epoxy resin, the wall thickness of the Helmholtz resonant cavity is 5mm, the inner diameter of the cavity body and the cavity neck are 100mm and 80mm respectively, and the height of the cavity body and the cavity neck are 30mm and 22mm respectively.

[0013] According to one embodiment of this application, the point defect acoustic metamaterial includes a pure aluminum substrate, silicone rubber resonant units, and a defect region; wherein, the substrate has a thickness of 0.4 mm and a diameter of 100 mm; the resonant unit is a stepped cross-section column made of silicone rubber, consisting of a top cylinder with a diameter of 8 mm and a height of 5 mm and a bottom cylinder with a diameter of 5 mm and a height of 5 mm coaxially connected, and the resonant unit is adhered to the surface of the substrate in a 6×6 periodic array with a lattice constant of 10 mm; the defect region is formed by removing four resonant units at the center position.

[0014] According to one embodiment of this application, the piezoelectric transducer uses a piezoelectric ceramic sheet with a thickness of 0.7 mm and a diameter of 10 mm. The ceramic sheet is fixed to the center of the defect area with conductive adhesive and connected to a load resistor through a wire to form a closed loop to output electrical energy.

[0015] According to one embodiment of this application, the piezoelectric ceramic sheet is a PZT-5H piezoelectric ceramic sheet.

[0016] This application also provides a method for detecting the energy-harvesting structure as described above, including: The resonant frequency of the Helmholtz resonant cavity is set to be consistent with the defect band frequency of the point defect acoustic metamaterial. External sound waves are incident from the neck of the Helmholtz resonant cavity, and after being resonantly amplified by the Helmholtz resonant cavity, they enter the point-defect acoustic metamaterial. The amplified sound wave accumulates acoustic energy in the defect area of ​​the point defect acoustic metamaterial. The accumulated acoustic energy is converted into vibrational energy by a piezoelectric transducer located in the defect area, and electrical energy is output through the piezoelectric effect.

[0017] According to one embodiment of this application, the method includes: the external sound wave is incident perpendicularly from the neck of the Helmholtz resonant cavity; the sound pressure amplification of the Helmholtz resonant cavity and the sound energy focusing of the defect band of the point defect acoustic metamaterial form a dual gain, thereby enhancing the sound energy density of the defect region; and the enhanced sound energy is converted into electrical energy through the piezoelectric transducer.

[0018] Compared with the prior art, the beneficial effects that at least one technical solution adopted in the embodiments of this specification can achieve include at least: 1. Breakthrough in low-frequency sound wave focusing: The acoustic metamaterial composed of stepped resonant pillars as scatterers can generate a lower frequency local resonant bandgap, shifting the defect band frequency down to the low-frequency range and significantly improving the low-frequency sound energy focusing capability.

[0019] 2. Dual-level gain synergistic effect: The sound pressure amplification of the Helmholtz resonator and the sound energy focusing performance of the point-defect acoustic metamaterial form a dual gain mechanism, which significantly enhances the sound energy density in the defect region and breaks through the energy conversion efficiency bottleneck of a single acoustic metamaterial.

[0020] 3. Multi-directional incident adaptability: The Helmholtz resonator cavity opening structure is compatible with multi-directional sound wave incident, expanding the range of sound wave energy capture, and is especially suitable for noise energy recovery needs in complex environments of aircraft.

[0021] 4. Industrial adaptability: The modular design uses a combination of lightweight materials (epoxy resin, aluminum substrate, silicone rubber), which combines structural compactness, mechanical stability and ease of manufacturing, making it easy to quickly integrate into aerospace equipment. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the Helmholtz resonator structure according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the acoustic metamaterial unit cell structure according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the supercell structure of the point-defect acoustic metamaterial according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the piezoelectric transducer structure according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the piezoelectric energy harvesting structure of a single-point defect acoustic metamaterial according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the piezoelectric energy harvesting structure of the coupling point defect acoustic metamaterial and the Helmholtz resonator cavity in an embodiment of the present invention. Figure 7 This is a graph showing the test data from an embodiment of the present invention; Among them, 1-cavity, 2-cavity neck, 3-substrate plate, 4-resonant unit, 5-piezoelectric transducer, 6-wire, 7-load resistor, 8-sound source. Detailed Implementation

[0024] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0025] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] like Figures 1-6 As shown, an embodiment of the present invention provides an energy-harvesting structure coupling an acoustic metamaterial and a Helmholtz resonator, comprising: The Helmholtz resonant cavity includes a cylindrical cavity 1 and a cavity neck 2 connected to the cavity 1. The bottom of the cavity 1 and the surface of the cavity neck 2 are provided with openings, and the opening at the bottom of the cavity 1 and the opening at the cavity neck 2 are arranged opposite to each other, so that the sound wave enters from the cavity neck 2 and then amplifies the sound pressure of the incident sound wave at the resonant frequency through the opening at the bottom of the cavity 1. A point-defect acoustic metamaterial is disposed at the opening at the bottom of the cavity 1, including a substrate plate 3 and a plurality of resonant units 4 arranged in a periodic array on the substrate plate 3. A defect region is disposed at the center of the plurality of resonant units 4. The defect region is formed by removing at least one resonant unit 4. The point-defect acoustic metamaterial is used to concentrate acoustic energy to the defect region at the defect band frequency. A piezoelectric transducer 5 is fixed at the center of the defect region. The vibration direction of the piezoelectric transducer 5 is perpendicular to the propagation direction of the sound wave in the acoustic metamaterial of the point defect. It is used to convert the accumulated sound energy into vibration energy through an external circuit and output electrical energy through the piezoelectric effect. The resonant frequency of the Helmholtz resonant cavity matches the defect band frequency of the point defect acoustic metamaterial to form a synergistic resonance effect, which causes the sound wave amplified by the Helmholtz resonant cavity to form sound energy focusing enhancement in the defect region.

[0027] The detection method for this energy-harvesting structure is as follows: the resonant frequency of the Helmholtz resonant cavity is set to be consistent with the defect band frequency of the point-defect acoustic metamaterial; external sound waves are incident from the neck of the Helmholtz resonant cavity, and after being resonantly amplified by the Helmholtz resonant cavity, they enter the point-defect acoustic metamaterial; the amplified sound waves accumulate acoustic energy in the defect region of the point-defect acoustic metamaterial, and the accumulated acoustic energy is converted into electrical energy by a piezoelectric transducer located in the defect region.

[0028] This invention provides a piezoelectric energy-harvesting structure that couples a point-defect acoustic metamaterial with a Helmholtz resonant cavity, solving the problems of insufficient acoustic energy focusing density and low energy conversion efficiency in existing technologies. The structure includes the following core modules: a cylindrical Helmholtz resonant cavity with sound pressure amplification characteristics; a point-defect acoustic metamaterial with periodically arranged stepped cross-section resonant pillars at the bottom of the resonant cavity; and a piezoelectric transducer 5 embedded in the defect region of the acoustic metamaterial. The core innovation of this invention lies in the synergistic resonance effect of the Helmholtz resonant cavity and the point-defect acoustic metamaterial, achieving dual gain of acoustic energy amplification and focusing, significantly improving energy conversion efficiency. Compared with existing technologies, this invention has advantages such as a compact structure, ease of manufacturing, ability to capture incident acoustic energy from multiple directions, and significantly improved energy harvesting efficiency.

[0029] Specifically, an embodiment of the present invention provides a piezoelectric energy harvesting structure for coupling a point-defect acoustic metamaterial with a Helmholtz resonant cavity, comprising three core components: a Helmholtz resonant cavity, a point-defect acoustic metamaterial, and a piezoelectric transducer 5.

[0030] The Helmholtz resonant cavity employs a cylindrical cavity structure with uniform wall thickness, featuring openings at the bottom and neck. It is made of epoxy resin with a wall thickness of 5mm. The inner diameters of cavity 1 and cavity neck 2 are 100mm and 80mm, respectively, and their heights are 30mm and 22mm, respectively, to achieve external acoustic isolation and multi-directional incident sound wave energy amplification. This resonant cavity amplifies the incident sound pressure at a specific frequency through resonance, achieving external acoustic isolation and multi-directional sound energy capture.

[0031] The point-defect acoustic metamaterial consists of a pure aluminum substrate 3 (0.4 mm thick, 100 mm diameter), a silicone rubber resonator 4, and a defect region. The resonator 4 is a stepped-section column, composed of a large-diameter segment and a small-diameter segment coaxially connected. The large-diameter segment is located away from the substrate 3, and the small-diameter segment is located closer to the substrate 3 and fixedly connected to it. Specifically, the resonator column is a stepped-section composite structure, with a cylinder of 8 mm diameter and 5 mm height at the top and a cylinder of 5 mm diameter and 5 mm height at the bottom, arranged in a 6×6 periodic array on the surface of the substrate 3 to form the acoustic metamaterial (lattice constant 10 mm). The defect region is formed by removing the four resonator columns at the center. This design causes the sound group velocity of the acoustic metamaterial to approach zero at the defect band frequency, resulting in highly localized acoustic energy within the defect region, forming a high-intensity acoustic energy focusing field.

[0032] The piezoelectric transducer 5 uses a piezoelectric ceramic sheet (such as PZT-5H) with a thickness of 0.7 mm and a diameter of 10 mm, which is precisely fixed to the center of the defect area with conductive adhesive. The wave focusing effect here places the piezoelectric transducer 5 directly in the area of ​​high acoustic energy focusing, maximizing the reception of focused acoustic energy and capturing vibration energy. A closed loop is formed by the wire 6 and the external load resistor 7, efficiently converting the focused high-density mechanical strain energy into electrical energy output.

[0033] The structural design of this invention strictly follows the following principles: the defect band frequency of the point defect acoustic metamaterial is consistent with the resonance frequency of the Helmholtz resonant cavity, forming a synergistic resonance effect and breaking through the limitation of low-frequency wave focusing efficiency of a single acoustic metamaterial.

[0034] The core principle of collaborative operation in this invention is as follows: When an external sound wave is incident perpendicularly onto the Helmholtz resonant cavity, the cavity first amplifies the sound pressure at the target frequency through resonance. Then, the amplified sound wave energy propagates through a point-defect acoustic metamaterial, resulting in high-density focused sound energy in the defect region. Finally, a piezoelectric transducer 5, embedded at the center of the defect, converts the focused high-density sound energy into electrical energy, which is then output through an external circuit.

[0035] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Figure 6 As shown, this invention provides a piezoelectric energy-harvesting structure of an acoustic metamaterial with coupling point defects and a Helmholtz resonator. This piezoelectric energy-harvesting structure consists of a Helmholtz resonator (such as...) Figure 1 As shown), point-defect acoustic metamaterials (such as...) Figure 2 and Figure 3 As shown), and piezoelectric transducer 5 (as shown). Figure 4 The three parts (as shown) are assembled and integrated. The component parameter configurations are as follows: Helmholtz resonant cavity configuration: A cylindrical Helmholtz resonant cavity made of epoxy resin with a wall thickness of 5mm; the inner diameters of cavity 1 and cavity neck 2 are 100mm and 80mm respectively, and the heights are 30mm and 22mm respectively, with a calculated resonant frequency of 1069Hz. The bottom and neck of cavity 1 are both kept open to achieve multi-directional sound wave capture and resonant amplification.

[0036] Configuration of the point-defect acoustic metamaterial: The pure aluminum substrate 3 is 0.4 mm thick and 100 mm in diameter. The stepped cross-section resonant pillars 4 are made of silicone rubber, with the top cylinder having a diameter of 8 mm and a height of 5 mm; the bottom cylinder has a diameter of 5 mm and a height of 5 mm. The substrate 3 and the resonant pillars 4 are bonded together with epoxy adhesive and arranged in a 6×6 periodic array on the surface of the substrate 3, with a lattice constant of 10 mm. A defect region is formed by removing the four resonant pillars at the center, with a side length of 20 mm. The calculated defect band frequency is 1069 Hz.

[0037] Piezoelectric transducer 5 configuration: The piezoelectric transducer 5 uses a piezoelectric ceramic sheet PZT-5H, with a thickness of 0.7mm and a diameter of 10mm. The piezoelectric ceramic sheet PZT-5H is fixed to the center of the defect area with conductive adhesive. Wires 6 are welded to the upper and lower electrode surfaces of the piezoelectric ceramic sheet and connected in series with the load resistor 7 to form a closed circuit. The output electrical energy is measured using an electrical energy testing device, such as... Figure 5 As shown.

[0038] Synergistic conditions and system integration: The resonant frequency of the Helmholtz resonant cavity and the defect band frequency of the point-defect acoustic metamaterial are both 1069 Hz, ensuring synergistic resonance conditions. The piezoelectric energy-harvesting structure of the point-defect acoustic metamaterial is tightly bonded to the bottom of the Helmholtz resonant cavity using epoxy adhesive, ensuring an unobstructed sound wave propagation path and a sealed cavity.

[0039] In this embodiment, the piezoelectric energy harvesting structure exhibits significant differences in energy output when the incident direction of the sound source 8 changes. When the sound source 8 is incident perpendicularly in the reverse direction from the neck of the Helmholtz resonator, only the point-defect acoustic metamaterial participates in piezoelectric energy harvesting, generating maximum acoustic energy accumulation at the defect band frequency of 1069Hz, at which point the output electrical energy reaches its peak. However, when the sound source 8 is incident perpendicularly in the forward direction, the Helmholtz resonator and the point-defect acoustic metamaterial work together, significantly increasing the output electrical energy through a two-stage gain (resonator sound pressure amplification + acoustic metamaterial wave focusing).

[0040] In B&K acoustic impedance tube tests, such as Figure 7As shown, when the excitation frequency is 1069 Hz and the incident sound pressure is 2 Pa: the maximum voltage captured by the reverse incident sound wave is 2.24 V, and the maximum power is 13.95 μW. The maximum voltage captured by the forward incident sound wave is 5.94 V, and the maximum power is 39.10 μW. The experimental data show that the voltage and power are increased by 2.65 times and 2.80 times respectively when the sound wave is incident forward, which fully verifies that the synergistic resonance effect of the Helmholtz resonator and the point-defect acoustic metamaterial can significantly enhance the low-frequency sound energy capture efficiency.

[0041] This embodiment verifies the core technical advantages of the present invention: through the synergistic resonance of the Helmholtz resonant cavity and the point-defect acoustic metamaterial, the piezoelectric energy harvesting structure provides a solution for aircraft noise energy recovery that is both engineering feasible and technologically groundbreaking, thanks to its high efficiency, lightweight, and easy integration characteristics.

[0042] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An energy-harvesting structure coupling an acoustic metamaterial with a Helmholtz resonator, characterized in that, include: A Helmholtz resonant cavity includes a cylindrical cavity and a cavity neck communicating with the cavity. The bottom of the cavity and the surface of the cavity neck are provided with openings, and the opening at the bottom of the cavity is opposite to the opening at the cavity neck, so that the sound wave enters from the cavity neck and then passes through the cavity to amplify the sound pressure of the incident sound wave at the resonant frequency. A point-defect acoustic metamaterial is disposed at the opening at the bottom of the cavity, comprising a substrate plate and a plurality of resonant units arranged in a periodic array on the substrate plate. A defect region is disposed at the center of the plurality of resonant units. The defect region is formed by removing at least one resonant unit. The point-defect acoustic metamaterial is used to concentrate acoustic energy to the defect region at the defect band frequency. A piezoelectric transducer is fixed at the center of the defect region. The vibration direction of the piezoelectric transducer is perpendicular to the propagation direction of the sound wave in the acoustic metamaterial of the point defect. It is used to convert the accumulated sound energy into vibration energy through an external circuit and output electrical energy through the piezoelectric effect. The resonant frequency of the Helmholtz resonant cavity matches the defect band frequency of the point defect acoustic metamaterial to form a synergistic resonance effect, which causes the sound pressure amplified by the Helmholtz resonant cavity to form sound energy focusing enhancement in the defect region.

2. The energy-harvesting structure for coupling acoustic metamaterials and Helmholtz resonators according to claim 1, characterized in that, The resonant unit is a stepped cross-section column, which is composed of a large-diameter section and a small-diameter section coaxially connected. The large-diameter section is located on the side away from the base plate, and the small-diameter section is located on the side close to the base plate and is fixedly connected to the base plate.

3. The energy-harvesting structure for coupling acoustic metamaterials and Helmholtz resonators according to claim 1, characterized in that, The external circuit is a closed loop formed by connecting the upper and lower electrodes of the piezoelectric transducer to an external load via wires.

4. The energy-harvesting structure for coupling acoustic metamaterials and Helmholtz resonators according to claim 1, characterized in that, The Helmholtz resonant cavity is made of epoxy resin, with a wall thickness of 5mm. The inner diameters of the cavity body and the cavity neck are 100mm and 80mm, respectively, and the heights of the cavity body and the cavity neck are 30mm and 22mm, respectively.

5. The energy-harvesting structure for coupling acoustic metamaterials and Helmholtz resonators according to claim 1, characterized in that, The point-defect acoustic metamaterial comprises a pure aluminum substrate, silicone rubber resonant units, and a defect region. The substrate has a thickness of 0.4 mm and a diameter of 100 mm. The resonant unit is a stepped cross-section column made of silicone rubber, consisting of a top cylinder with a diameter of 8 mm and a height of 5 mm and a bottom cylinder with a diameter of 5 mm and a height of 5 mm, coaxially connected. The resonant units are adhered to the surface of the substrate in a 6×6 periodic array with a lattice constant of 10 mm. The defect region is formed by removing four resonant units at the center.

6. The energy-harvesting structure for coupling acoustic metamaterials and Helmholtz resonators according to claim 1, characterized in that, The piezoelectric transducer uses a piezoelectric ceramic sheet with a thickness of 0.7 mm and a diameter of 10 mm. It is fixed to the center of the defect area with conductive adhesive and connected to a load resistor through a wire to form a closed loop to output electrical energy.

7. The energy-harvesting structure for coupling acoustic metamaterials and Helmholtz resonators according to claim 6, characterized in that, The piezoelectric ceramic sheet is a PZT-5H piezoelectric ceramic sheet.

8. A method for detecting a piezoelectric energy-harvesting structure as described in any one of claims 1 to 7, characterized in that, include: The resonant frequency of the Helmholtz resonant cavity is set to be consistent with the defect band frequency of the point defect acoustic metamaterial. External sound waves are incident from the neck of the Helmholtz resonant cavity, and after being resonantly amplified by the Helmholtz resonant cavity, they enter the point-defect acoustic metamaterial. The amplified sound wave accumulates acoustic energy in the defect area of ​​the point defect acoustic metamaterial. The accumulated acoustic energy is converted into vibrational energy by a piezoelectric transducer located in the defect area, and electrical energy is output through the piezoelectric effect.

9. The detection method according to claim 8, characterized in that, include: The external sound wave is incident perpendicularly from the neck of the Helmholtz resonator. The sound pressure amplification of the Helmholtz resonator and the sound energy focusing of the defect band of the point defect acoustic metamaterial form a dual gain, which enhances the sound energy density of the defect region. The enhanced sound energy is then converted into electrical energy through the piezoelectric transducer.

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