A brief review of sound energy harvesting

Sound energy harvesting is one of the promising technologies due to the abundant and clean sound sources. It can be the semi-permanent alternative power supplies for wireless sensor networks (WSNs), which is significant in the Internet of Things (IoT). However, sound waves have the low energy density, so there are many kinds of research in recent years to overcome this problem. This paper provides a comprehensive review of sound energy harvesting, focusing on presenting principles, examples and enhancement methods of sound energy harvesters. In this paper, various approaches are introduced which are classified as sound pressure amplification and transduction mechanism. For sound pressure amplification, two typical types of energy harvesters are presented that one is using a resonator, another one is using an acoustic metamaterial, and these are based on piezoelectric, electromagnetic, and triboelectric mechanisms to convert sound energy to electrical energy.