Echoes are caused by the reflection of sound. A sound wave will continue to bounce around or reverberate until it has lost all its energy. A wave has some of its energy absorbed by the objects it hits. The rest lost as heat energy.
The phenomenon of the reflection of sound is used to determine the distance between the two objects, for example depth of seabed, depth of cave or width of a valley. The type of sound used must be ultrasound.
Sonar (Sound Navigation and Ranging). Sonar is used to detect underwater objects (corals / fishes) or to determine the depth of the water by means of an echo. Sonar equipment emits a high frequency sound signal which is reflected by the object in the water. The reflected sound wave is received by the sonar receiver. The time taken for the echo to return is used to determine the distance of the object below the water surface.
Sonar waves of high frequency is used because it possesses more energy, high penetration power and can travel further through water.
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