Highly-efficiency low-frequency acoustic energy harvesting with PDMS-modified loudspeakers

Noise is everywhere in our lives. Low-frequency noise in particular has a conspicuous if not disturbing presence since thicker materials are required to absorb or block it. Meanwhile, the very ubiquitousness of noise in our environment makes it a good candidate as a potential power source for micro-devices. Here we present an acoustic energy harvester (AEH) capable of achieving 99% sound absorption coefficient and 67% of energy conversion ratio at 58 Hz, with a fractional bandwidth of more than 34 %. The peak power conversion efficiency is nearly three times the previous state of the art. The harvester is made from an electrodynamic loudspeaker driver retrofitted with a custom-made PDMS surround for lower mechanical loss on the diaphragm. The low cost (<$50) makes our AEH suitable for large-scale deployment.