Many research groups across the world are in the process of developing so-called ‘Energy Harvesting’ (EH) techniques to extract electrical energy from human actions. (see for example, Implementing a knee-energy harvester). The Choo Lab at Caltech specializes in such things, and researchers there have recently developed a system which is designed to power portable electronic devices by extracting useful energy from vibrations originating in human vocal cords. To be specific, it’s a humming generator.
Harvesting energy from participants who hummed* at 75dB (i.e. around normal voice levels) for 10 minutes, a test prototype was able to generate enough power to charge a battery and “operate a 10-LED array (power consumption: 2.2 V, 10 mA) […] for about a minute.” Or, put another way, enough to illuminate one LED for ten minutes. That’s to say, the device can continuously power an LED, providing its wearer keeps humming.
“Our energy harvesting method will provide a practical and efficient way to harvest energy to power portable electronics anywhere without additional charging apparatus.“
– say the team. Details are published in : ‘Powering Portable Electronics Using Vocal Fold Vibrations’, Cho, Hyunjun, Kyoo Hyun Noh, Tomohiro Ishikawa, Daejong Yang, Edgar Sanchez-Sinencio, and Hyuck Choo. IEEE MEMS, Jan 22–26, 2017, Las Vegas, NV (Oral Presentation).
*note: Also works with shouting (and, presumably, singing)
For another recent example of EH see: ‘A non-resonant, gravity-induced microtriboelectric harvester to collect kinetic energy from low-frequency jiggling movements of human limbs’ Yingxian Lu, Xiaohong Wang, Xiaoming Wu, Jin Qin and Ruochen Lu. Journal of Micromechanics and Microengineering, Volume 24, Number 6.
Also don’t miss Trumbull and Johnston’s patented tooth generator