Reflection of sound waves against room boundaries and objects within the room persisting after the original sound has ceased. Reverberation is essentially an echo. Think of waves in a bathtub. They run across the surface to the end of the tub, hit the tub wall, bounce back, hit the opposite tub wall, bounce back, and so on for some time. This effect is reverberation. Reverberation is increased by hard surfaces such as wood floors or stone fireplaces and decreased by soft, absorbing materials such as rugs, carpet and sofas.