Propagation of a Simple Transient in an Isovelocity Layer with Pressure-Release Boundaries.
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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The propagation of a simple acoustic transient in an isovelocity water layer was investigated for the purpose of studying the region of validity of a suggested correlation between exact solutions in ducts and solutions for propagation in a layer. The Laplace transform method was used to obtain approximate solutions for the acoustic pressure, particle velocity, and particle displacement resulting from a step-function input in velocity. The radiation impedance characteristics of a Mylar transducer were investigated to study their effect on the received waveforms. Computer programs were written to evaluate and graph the resulting waveforms. The waveforms resulting from a step-function input in velocity were observed and compared with the predicted waveforms. With the use of a family of Mylar transducers, a somewhat doubtful correlation was obtained in the region of validity of the theoretical solutions. Possible causes of the disagreement between the theory and the experiment were investigated. It was found that the theory is believed to be correct, that the experiment was not accurate enough, and that further investigations should be conducted to study the assumed pressure-release characteristics of 14 inch polyethylene. Author