1.3 Sound That Lingers
Reverberation
Absorption occurs when a sound wave is absorbed by the object or material it encounters. A sound wave that is absorbed transforms into heat energy inside the object or material absorbing it. How much energy gets absorbed or continues to travel onward depends on the thickness and nature of the material. Too little absorption causes sound to reflect.
Echo
Echoing indoors can make conversation difficult, and amplify distracting sounds. When reverberation time is long enough, an echo can occur. An echo is the distinct repetition of an original sound produced through the reflection of sound waves, which arrives at the listener following a delay. The length of the delay depends on the distances between the reflecting sound surface, the sound source, and the listener. One type of echo that is particularly problematic is a flutter echo. A flutter echo is the phenomenon of sound energy becoming trapped and reflecting repeatedly between two parallel surfaces, such as in a hallway.
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