Nature:
An "acoustic rectifier" has been developed by a group of
researchers at Nanjing University in China, who published their
results yesterday in
Nature Materials
. According to
Nature's Daniel Cressey, the device allows sound to
travel in only one direction, in the same way that electronic
diodes allow current to move in only one direction. When sound
waves hit a layer of ultrasound gel, it converts some of the
energy of the acoustic wave into a wave of double the
frequency, and then a lattice of alternating layers of water
and glass screens out all frequencies except the second, higher
frequency. The device could be useful for medical ultrasound
applications.
