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10 May 2017

New Graphene Speaker Creates Sound through Heat

The use of graphene in speakers is nothing new; being incredibly thin, strong and lightweight, it’s the ideal material for use in the vibrating membranes which distort the air in specific patterns in order to generate sound waves. But, what about removing the need for movement altogether? Researchers at the University of Exeter have found a way to do just that with the creation of a new thermal speaker, which uses heat to carefully manipulate electric currents to create sound.

Img: University of Exeter
The new device contains a speaker, amplifier and graphic equaliser, all contained within a single chip no bigger than a human thumbnail. This is made possible by the remarkable conductive properties of graphene, which allow for the rapid, sequenced heating and cooling of the material via the use of specific electrical pulses. The heat is then converted into sound through a process known as thermoacoustics, as the variable temperature affects the air around the membrane, which expands and contracts to generate sound waves.

According to the research team responsible for the creation of the new device, the thermal speaker is able to create “a rich sonic palette” by carefully controlling the flow of electricity through the graphene. Not only does this make it capable of creating a sound quality comparable to, if not better than conventional speakers, it is also able to mix, amplify and equalize multiple sound frequencies at the same time. This could see its output boosted beyond the range of human hearing and even open up ultrasound applications.

David Horsell, lead author of the study, said of the new device and its potential, “Thermoacoustics has been overlooked because it is regarded as such an inefficient process that it has no practical applications. We looked instead at the way the sound is actually produced and found that by controlling the electrical current through the graphene we could not only produce sound but could change its volume and specify how each frequency component is amplified. Such amplification and control opens up a range of real-world applications we had not envisaged.

“The sound generating mechanism allows us to take two or more different sound sources and multiply them together,” continued Horsell. “However, the most exciting thing is that it does this trick of multiplication in a remarkably simple and controllable way. This could have a real impact in the telecommunications industry, which needs to combine signals this way but currently uses rather complex and, therefore, costly methods to do so.”

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.