You can actually buy commercial products that are powered by sound. Sound is actually a pretty great power source for wireless sensor nodes that monitor loud pi

You can actually buy commercial products that are powered by sound. Sound is actually a pretty great power source for wireless sensor nodes that monitor loud pieces of machinery. Sure, you don't get much power, but for a sensor node you don't need much either. Sometimes sound is the only source of power you can get for such things where it's too dark or parts need to move relative to each making wires difficult. Plus, sometimes you want to monitor the very same vibration that's giving your sensor power. Now the thing that really gets me is some work I saw on developing a vibration powered sensor for highway bridges. So the best power source they found was a small wind turbine. But when they tried them out on a bridge out in the middle of nowhere, the problem was they were just too much of an entertaining object for people to shoot. So they made this rather large pipe with a magnet on springs inside and were able to harvest energy from the low frequency vibrations of the bridge moving around. [0]https://www.microgensystems.com/ https://www.microgensystems.com/ [1]http://www.ni.com/white-paper/12128/en/ http://www.ni.com/white-paper/12128/en/