Microphones guzzle electricity. Could it be possible that arriving sound waves simultaneously generate the required power? Boston-based startup [link url=http://vespermems.com/ target=_blank] Vesper[/link] came up with this idea. Since sound consists of pressure waves, the young company counts on piezoelectric microphones. They are the size of two sesame seeds, self-sufficient for several days and even work underwater – you can use them to [link url=https://www.youtube.com/watch?v=g-XMigDK_WA target=_blank] listen to lemonade bubble[/link].