Reverberation

When active sonar is used, spreading occur from small objects in the sea as well as from the bottom and surface. This can be a main source of interfering but does not occur with passive sonar. This scattering cause is different from that in room reverberation which is a reflection incident. An analogy for reverberation is the diffusion of a car's headlights in fog or mist. A high-intensity pencil beam will break in the fog; main headlights are less directional and where the returned noise dominates. Similarly, to overcome reverberation, an active sonar requests to transmit in a narrow beam.