Thousands of marine species from microscopic zooplankton to the largest cetaceans rely on sound for survival and many have ...

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.

The process is very similar to ultrasound imaging. However, the sound waves used are within normal hearing range, and they are used to identify objects rather than internal structures. This ...