The term reverberation explained

The noun reverberation refers to the repetition of sound resulting from reflections of it waves. The phenomenom of reverberation is difficult to explain in terms of physics. My Oxford Dictionary of Physics (2003 edition) only has an entry for “reverberation time”:

The time taken for the energy density of a sound to fall to the threshold of audibility from a value 10⁶ times as great; i.e, a fall of 60 decibels. It is an important characteristic of an auditorium. The optimum value is proportional to the linear dimension of the auditorium.

If something starts reverberating in your head now, you might prefer the following explanation of reverberation by Don and Florence Leet, which I really like since it illustrates the concept in a few vivid sentences:

If sound hits a mountain, wall, or other solid surface some of it bounces back. This bouncing off is called “reflection” or “echoing.” And when it takes place back and forth and up and down in a room, we call it “reverberation.” The great difference between the sound of things in open air and in a room or auditorium is that in the open, there is no reverberation and inside there is.

Keywords: acoustics, sound waves, reflection

Reference
L. Don and Florence Leet: Earthquake • Discoveries in Seismology. Dell Publishing Co., Inc, 750 Third Avenue, New York, N. Y. , 10017, USA, 1964; pages 61 and 62.