An acoustic energy harvester using a coupled resonance structure of a sonic crystal resonator and an electromechanical Helmholtz resonator with a piezoelectric composite diaphragm is proposed to enhance energy harvesting. Due to acoustic resonance coupling between the sonic crystal resonator and the Helmholtz resonator, the coupled resonance structure has a larger acoustic pressure magnification than each individual resonator structure. Consequently, the stronger vibration of the diaphragm and the higher harvesting efficiency are obtained. Experimental results show that the proposed harvester exhibits ∼23 and ∼262 times higher maximum harvesting efficiencies than the sonic crystal resonator and the Helmholtz resonator structure, respectively.

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A high-efficiency broadband acoustic energy harvester consisting of a compliant-top-plate Helmholtz resonator (HR) and dual piezoelectric cantilever beams is proposed. Due to the high mechanical quality factor of beams and the strong multimode coupling of HR cavity, top plate and beams, the high efficiency in a broad bandwidth is obtained. Experiment exhibits that the proposed harvester at 170-206 Hz has 28-188 times higher efficiency than the conventional harvester using a HR with a piezoelectric composite diaphragm. For input acoustic pressure of 2.0 Pa, the proposed harvester exhibits 0.137-1.43 mW output power corresponding to 0.035-0.36 μW cm(-3) volume power density at 170-206 Hz.

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