Joint acoustic energy harvesting and noise suppression using deep-subwavelength acoustic device

Aiming to simultaneously realize acoustic energy harvesting (AEH) and noise suppression, this study proposes a novel deep subwavelength acoustic device. The proposed device is composed of an acoustic resonator with a compliant bottom. At the acoustic resonance frequency of the device, sound pressure difference will excite the compliant part and generate substantial strain energy within the substrate. The electrical energy is then generated from the bonded piezoelectric patch on the substrate. Specifically, an embedded logarithmic spiral neck is adopted to make the device compact. Moreover, compared to the uniform neck configuration, the proposed spiral configuration is able to improve sound pressure amplification performance, which is demonstrated via numerical simulation and experimental studies. For the single AEH unit performance, experimental results show 8.1 μW electrical power can be harvested at 100 dB sound pressure level (SPL) excitation. At the acoustic resonant frequency, the proposed device is deep subwavelength, which is only 1/76 of the interested wavelength. Furthermore, when the AEH array configuration is adopted, simultaneous noise and energy harvesting functions can be realized. Experimental results show that the acoustic energy can be converted into electrical power, which is able to power a pedometer device. Meanwhile, the noise reduction performances concerning different excitation cases are notable. The proposed AEH system saves space and is multifunctional, which can be applied to the industrial application in the near future.