Masters of Science:
Underwater Acoustics Signal Processing

A thesis submitted to the University of Auckland
in partial fulfilment of the requirements for the degree of
Master of Science in Physics
University of Auckland
By Paul Bourke, Physics Depeartment, University of Auckland
Submitted February 1985, Awarded March 1985


An experiment was performed in 1982 by the Auckland University Physics Department to investigate underwater acoustic propagation in a shallow water environment. The ocean channel was excited using a low frequency acoustic source and the pressure field in the water was measured by a vertical array of six hydrophones.
A stepped frequency modulated chirp was used as the source signal allowing measurements of the frequency response of the acoustic channel over a frequency range from 30Hz to 300Hz. The response of the water channel at each hydrophone depth to a pulse can therefore be determined and comparisons made with that predicted by mode theory.
Ray modelling is successfully applied at close ranges to determine the source-receiver range and the water depth. Estimates are also made of the sound speed in the bottom layer.