A group of people at the Tokyo University of Ag and Tech has come up with a solid state speaker that can blare out noise at up to 150 kilohertz.
According to nikkei.net, the ultrathin device is only 2.8 microns thin and of course humanoids like you and me can’t possibly hear sounds at this pitch.
But that doesn’t mean the device has no applications, the wire said. For example it could act as a sonar like device and for crime prevention.
What about the tech? Nikkei says it’s made on a substrate of single crystal silicon with nanocrystalline silicon deposited on it and components made from tungsten and aluminium. Apply some juice to the aluminium and the surface temperature changes, producing sound waves.
According to this page, birds and humans hear best at frequencies between 2KHz and 4KHz. This page says bats can hear between 20 and 200KHz. So we’re a bit worried that the bats might be deafened by this solid state gizmo. The nikkei.net story is here (subscription needed). Picture of bat on front page courtesy of Wikipedia.