Echolocation

Echolocation is used by dolphins and bats to find their way. They use high frequency sound and its reflection to image the environment.

In a previous episode of criminal minds, I learned that very same technique is also being used by some blind people. To make such a sound, they  push their tongue to their palate and pull it back swiftly. Frequency of this sound can not be compared to those of dolphins and bats but it has a high frequency. After some training, people can understand place, dimension and density of objects around them with the echo of this sound.