It could go down as one of the most irritating inventions in history!

Scientists have devised a gadget that will allow mobile phones to be recharged simply by talking into them. The technology turns sound into electricity, allowing a mobile to be powered up while a conversation is in progress – and the greater the volume the greater the charge.

The invention is billed as a godsend for those who regularly suffer the frustration of flat batteries. But there are fears it will simply be an excuse for inconsiderate phone-users to make even more annoyingly noisy calls in public places. The technology could also be used to power up personal music players, raising the possibility of charging an iPod by singing along to your favourite songs.

Dr Sang-Woo Kim, of Sungkyunkwan 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 – the main ingredient of calamine lotion – sandwiched 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. This generates electrical current that can then be used to charge a battery. Devices made so far can convert sounds of around 100 decibels – the equivalent of noisy traffic, a passing train or a nearby lawnmower – into a mild electrical current.

Full story, other source 1, source 2