UK team uses graphene to convert heat into sound

(Credit: David Horsell/University of Exeter)

Speakers usually generate sound through mechanical means, with coils or membranes physically pushing air. The new device, described in the journal Scientific Reports, has no moving parts. Instead, a layer of graphene is rapidly heated and cooled by an alternating electric current. This thermal variation causes the air to expand and contract, creating sound waves.

Although using heat to generate sound is not new, the Exeter team claims it is the first to demonstrate that the process allows different frequencies to be mixed, amplified and equalised, all within a millimetre-sized device. According to the researchers, the ability to generate complex sounds without physical movement could open up new areas of technology, such as smartphone screens that deliver sound as well as pictures.

"Thermoacoustics has been overlooked because it is regarded as such an inefficient process that it has no practical applications,” said lead author Dr David Horsell, senior lecturer in Exeter’s Quantum Systems and Nanomaterials Group.