In the case of a sound wave in air hitting a solid wall, most of the sound is reflected back. That is enough to be able to distinguish between the noise you made and the reflected sound. Echoes can be used to tell how far away an object is, how fast the object is moving, and even its shape. By knowing the speed of sound and measuring the time it takes to hear the echo, you can calculate the distance of the object. Sonar A sonar device sends out a sound and automatically calculates the distance of an object.
Submarines use sonar to find objects under the water, including other submarines.
Fishermen also use sonar to find schools of fish. Sonar and radar work on the same principle. Sonar uses sound waves , while radar uses electromagnetic waves . When a wave bounces off a moving object, the wavelength changes according to the velocity of the object. If the object is moving toward you, the wavelength gets shorter or the pitch of the sound gets higher.