A reverberation is a reflection of a sound wave which reaches the listener's ear so quickly that he or she has trouble distinguishing between the reverberation and the original sound. Reverberations also usually occur in groups, and over time, the nature of the sound may change as the sound wave degrades. One of the best examples of a reverberation can be experienced by singing in a shower; after one stops singing, sound can still be heard as the sound waves echo around the shower and are gradually absorbed.
People experience reverberation almost every time they hear a sound, although they may not be aware of it. Sound waves rarely travel in a straight line to the ear of the listener from the origin. Instead, they bounce around. In a room, for example, someone standing directly in front of a speaker will hear sound from a speaker, but he or she will also experience reverberations as sound waves traveling at different angles bounce around the room, reflecting from the walls, furniture, and other people.
In a space which is said to have “good acoustics,” the space has been carefully designed to bring out the best qualities of reverberation without highlighting some of the worst ones. Spaces with poor acoustics have spatial layouts and designs which tend to turn sound muddy and weak, or which amplify sound. Both distortions of sound can be unpleasant or painful to the ear, making the space unsuitable for musical performances and sometimes unpleasant for casual use, as in an art gallery in which sound gathers and amplifies, causing art openings to be extremely noisy with loud overlapping chatter.
Some reverberation is also integrated into music. Recording studios are specifically designed to create the ideal level of reverberation, and devices can be fitted to instruments to tweak the level of “reverb” as it is known. Reverberation can be used to create an effect of a prolonged note or sound when the original sound is actually quite short, or to play with a sound as the wave degrades.
Echoes are not the same thing as reverberations, although the two concepts are very similar. Echoes are also reflections, but people experience a noticeable time delay when they hear an echo, experiencing the original sound, a break, and then an echo. Echoes may occur multiple times as the sound moves around a space and reflects, but they do not blend together to trick the ear of the listener into thinking that a single sustained sound is occurring.