1. Multiple reflection in a layer, usually the water layer in marine work; ringing; singing. Sometimes the term is reserved for the case where the successive multiples blend together into a more-or-less steady oscillation; occasionally it includes also the situation where the water is so deep that the successive multiples are discrete. Reverberation sometimes occurs on land records also. Removing reverberation effects may be an objective of deconvolution. See Sheriff and Geldart (1995, 165–166, 169). 2. The effect of a long oscillatory source such as sometimes occurs with explosive or air-gun (or other) sources.