Waves have the property of being reflected when they meet an obstacle. When a sound wave is reflected by a distant obstacle, such as a wall or a cliff, an echo is heard. For an echo to be heard separately from the original sound, it must arrive 0.1 sec after the original sound is made. This can happen if the minimum distance of the reflecting surface from the source sound is 17 metre. If the distance is less than 17 metre, the echo cannot be distinguished as a separate sound and gives the impression of the original sound being prolonged. This prolonging of sound by reflection is called reverberation. Reverberation is also caused when a series of echoes are heard due to more than one reflecting surface.
An echo can be used for measuring the speed of sound. Exploration of underwater gas and oil is done by detecting the echoes of shock waves produced by explosions on the water surface. Echoes of ultrasonic waves are used for measuring the depth of sea-beds or locating submerged objects. An apparatus called Sonar (Sound Navigation Ranging) is used for this purpose.
Ultrasonic is also used for detecting flaws in the interior of solids, destroying micro-organisms, and mapping underground structures for oil and mineral deposits.
An echo can be used for measuring the speed of sound. Exploration of underwater gas and oil is done by detecting the echoes of shock waves produced by explosions on the water surface. Echoes of ultrasonic waves are used for measuring the depth of sea-beds or locating submerged objects. An apparatus called Sonar (Sound Navigation Ranging) is used for this purpose.
Ultrasonic is also used for detecting flaws in the interior of solids, destroying micro-organisms, and mapping underground structures for oil and mineral deposits.
