Harvesting ambient acoustic energy using acoustic resonators

Abstract

Sound is abundant in our everyday life, especially in urban environments. Despite the prevalence of sound, it is difficult to harvest acoustic energy in practical applications due to its low power density. In this study, we conduct numerical calculations to maximize the stored energy in piezoelectric beam arrays placed inside a Helmholtz resonator. The shape of the Helmholtz resonator is optimized to be a tube in order to increase the sound pressure amplification factor and lower the eigenfrequency to ∼400 Hz. When the tube resonates by an external sound, the piezoelectric beams vibrate by amplified standing wave resulting in generating electrical energy. The simulation results show that a single beam is able to store ∼0.0569 μJ strain energy when it is placed near the tube inlet with the incident sound pressure level of 100 dB. Using nine piezoelectric beams increases the total strain energy to 0.382 μJ. © 2011 Acoustical Society of America.