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Be it water, light or sound: waves usually propagate in the same way forwards as in the backward direction. As a consequence, when we are speaking to someone standing some distance away from us, that ...

A sound wave is a vibration that travels through a solid, liquid or gas such as the air or water. A loud sound has a large amplitude, a high pitched sound has a high frequency. Musicians and ...

The metamaterial structure the team designed is made of a single linear elastic material. (Courtesy: Yi Chen, KIT) An unusual type of sound wave that can travel backwards in space and has previously ...