So far we have only considered sound in isolation and we have seen that sound has velocity, frequency, wavelength and reduces in intensity in proportion to the square of the distance from the source.

Ultrasound scans could soon be much more detailed, thanks to a novel material that can bend sound waves the “wrong” way. This property, known as negative refraction, means the material should bring ...

Two physicists in China have shown that it should be possible to observe negative refraction with sound waves. Xiangdong Zhang of Beijing Normal University and Zhengyou Liu of Wuhan University have ...