Accoustic diode

This is a device that allows one-way propagation of sound. Obviously, such device must break time reversal symmetry. [http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.106.084301]

The device consists of a two-dimensional sonic crystal arranged in a mesh of square steel rods. By rotating the steel rods, Li et al. are able to manipulate the unit cell of the sonic crystal element to turn the diode on (sound waves only propagate one way) and off (sound waves can move back and forth). Furthermore, Li et al. make their device entirely from linear acoustic materials, which allows them to control sound propagation with a simpler and more efficient process, over a broader bandwidth, and with lower power consumption, compared to existing nonlinear sonic-crystal-based devices.