According to Daily Mail, the technology could also be used to power up personal music players by singing along to your songs. However, there are fears that this will cause a noise pollution in public areas due to the fact that mobile users “shout” at the phone to recharge faster.
Dr Sang-Woo Kim, of University in Seoul, South Korea, said that just as speakers transform electric signals into sound, the opposite process of turning sound into a source of electrical power is possible.
Dr Kim’s device uses tiny strands of zinc oxide between two electrodes. A sound-absorbing pad on top vibrates when sound waves hit it, causing the tiny zinc oxide wires to compress and release the electricity. Devices made so far can convert sounds of around 100 decibels – the equivalent of noisy traffic, a passing train or a nearby lawnmower.
Meanwhile, U.S. scientists are working on a gadget that converts the movement of the knees while walking into electricity. 

Source: vnExpress.net