I'M ON THE TRAIN!

Sorry to shout, but that sort of inconsiderate mobile phone use may actually have some purpose in future if researchers have their way. Scientists at Sungkyunkwan University in Seoul, South Korea, are working on a device which will use the sound waves from your voice to help charge a mobile phone. Of course sound waves are already converted to electricity in a mobile phone -- that's how the voice signal is transmitted -- but reasearchers hope there may be some "spare change" to actually charge the battery.

Dr Sang-Woo Kim said: ‘A number of approaches for scavenging energy from environments have been intensively explored. The sound that always exists in our everyday life and environments has been overlooked as a source. This motivated us to realise power generation by turning sound energy from speech, music or noise into electrical power.’

The research team are currently using zinc oxide for the energy harvesting device. Currently -- perhaps predictably -- they are not getting enough energy to charge the phone fully but are hoping to experiment with other materials.