Pretty soon the bloke who is shouting “I am on the train” might simply be charging his phone, rather than being an annoying tosser who should be first against the wall when the revolution comes.
Boffins have worked out how to turn energy from sound into electricity and this might open the way for mobiles to be charged by actually talking.
South Korea’s Dr Sang-Woo Kim of Sungkyunkwan University in Seoul has developed a prototype of the technology that can convert sound of around 100 decibels into 50 millivolts of electricity.
While this is not enough to charge much, it is early days in the technology’s development.
What he did was shove zinc oxide wires between two electrodes and a pad on top vibrates when hit by sound waves. This causes the wires to compress and release, generating an electrical charge for small devices such as mobile phones.
If a sound is really loud it can generate more juice.
It is not just mobile phones either. If you built sound-insulating walls near motorways you could generate electricity from the sound of passing vehicles.
Still, if shouting at your phone generates electricity, the gunshots of commuters turning militant on the train bloke for charging his phone should generate a few millivolts too.