A prototype device he used generated 50 millivolts of electricity from about 100 decibels of sound.
The device uses tiny strands of zinc oxide placed between two electrodes, with a sound-absorbing pad on the top. The pad vibrates and moves when it's hit by sound waves,which squishes the zinc oxide strands. The strands then spring back.
It's that movement that generates an electrical current.
Apparently, 100 decibels of sound generated 50 millivolts of electricity. One millivolt is a thousandth of a volt.
Semiconductors have smaller band gaps than insulators. They conduct electricity at room temperature.
A band gap, also called an "energy gap," is an energy range in a solid where no electron states can exist. It generally refers to the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors.
While it will be a while before it can power a phone. still a cool concept.