COMMUNICATION CHARACTERISTICS OF AN UNDERWATER ACOUSTIC SIGNAL REFLECTED FROM A SPACE AND TIME RANDOM SURFACE.

This dissertation is concerned with a portion of the general underwater acoustics communication problem, namely the communication channel defined as the path from a transmitter to receiver via a single reflection from a surface which is random in space and time. A winddriven random surface is produced in a model tank and is shown to closely approximate the ocean surface. The following results are of particular interest 1 for a continuous sinusoidal signal reflected from the surface, the envelope of the received signal has a frequency spectral bandwidth greater than the bandwidth of the amplitude of the surface measured near the sonified area 2 crosscorrelations observed between envelopes of an amplitude modulated transmission signal and envelopes of the received signal are low but finite indicating that although considerable distortion is introduced by the random surface, the channel can be used for communication and 3 no correlation was found between the height variations of the surface and the envelope of the received signal.