A standard home audio speaker converts electrical signals into sound pulses in the air (via a somewhat cumbersome cone). Those sound waves in turn cause tiny variations in air temperature, as waves disrupt surrounding air. So, scientists reasoned, why not create sound waves through those temperature fluctuations themselves?
In 2008 researchers built a loudspeaker from carbon nanotubes that creates sound from this thermoacoustic effect. Now Finnish researchers have created a far more simple thermoacoustic device using tiny aluminum wires suspended over a substrate, opening thermoacoustics to a far broader range of applications.