Sound waves can reflect off surfaces. We hear reflected sound waves as echoes. Hard, smooth surfaces are particularly good at reflecting sound. This is why empty rooms produce lots of echoes.

in order to avoid unwanted reflections of light or microwaves. Ten years ago, researchers succeeded in suppressing sound wave propagation in the backward direction; however, this also attenuated ...

A team of researchers has found a way to make sound waves propagate in one direction only, which could help avoid unwanted ...