The study of acoustic noise and the reverberation of acoustic signals is of importance because one or other of these phenomena will set the limit to sonar system performance. Whilst it is true that both sources of corruption can co-exist, it is most common to find that one of the two will predominate. Notice that in a noise-limited sonar, increasing the signal power will improve the signal-to-noise ratio and hence the system performance. The same need not be true for a reverberation limited sonar, since the reverberation is, itself, directly a function of the output signal level.