Phone needs charging? Just yell at it

As if it weren’t irritating enough to have to listen to people on their mobile phones, a South Korean team has just given people an excuse to yell into them even more loudly.

Dr Sang-Woo Kim, of Sungkyunkwan University in Seoul, has devised a technology that allows phones to be charged simply by talking to them – and the louder the noise, the more quickly the phone will charge.

The system works by transforming sound into electrical signals. The sound causes the pad on top of the phone to vibrate, compressing and releasing tiny zinc oxide wires which then generate current.

“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,” he says.

“This motivated us to realise power generation by turning sound energy from speech, music or noise into electrical power.”

So far, the technology requires a lot – and we mean a lot – of noise. It takes over 100 decibels – the equivalent of a train passing nearby – to create a 50 millivolt current, which still isn’t enough to charge a phone.

But the scientists are working on improving this through the use of different materials for the wires, and say they’re hopeful of success. In the meantime, they say, the system could be used for lower-power devices.

“Our current output performance can be applied to various electronic devices with low-power consumption such as self-powered sensors and body-implantable tiny devices,” says Kim. “We believe that we can realise more efficient sound-driven nanogenerators.”

Kim says the technology could also be used on a larger scale through the installation of sound-absorbing walls alongside major roads. These could not only generate electricity, but would have the added advantage of reducing noise levels.