Results of Volume-Reverberation Tests

Reverberation tests were conducted as part of an over-all NAVAIRDEVCEN program for improving both sonar systems and the capability for predicting system effectiveness. A 15.4-kHz sound source was used to investigate volume reverberation levels as a function of source level, pulse length, and FM sweep width. Explosive sound sources were used to investigate diurnal variation and the spectral distribution of reverberation levels. The data show that the relationship between volume-reverberation level and source level is linear. An equation is empirically derived that expresses a less-than-linear dependence of volume reverberation levels on pulse length. The amplitudes of the deviations from the mean levels are shown to be lower for the FM mode than the sinusoid mode and inversely proportional to the swept bandwidth. The mean levels, however, exhibit no significant differences. Nighttime reverberation levels for the systems used are shown to be significantly higher than daytime levels.