Title

Experimental measurements of acoustic intensity fluctuations in a shallow water environment

Date of Award

2000

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Applied Marine Physics/Ocean Engineering

First Committee Member

Harry A. Deferrari, Committee Chair

Abstract

Fluctuations observed in complex acoustic signals collected during the SWARM 95 experiment are analyzed and related to variability in the oceanographic environment. Acoustic data were collected on a 32 element vertical receiver array which spanned the 89 meter water column from depths of 23 to 85 meters. The receiver array was located 42 km seaward from two fixed acoustic projectors which transmitted a 224 Hz PRN signal (16 Hz bandwidth) and a 400 Hz PRN signal (100 Hz bandwidth). Evidence is presented that short term (<30 minutes) acoustic fluctuations are the result of mode coupling due to scattering from the internal tide and the associated internal gravity wave soliton packets and long term (semi-diurnal) acoustic fluctuations are the result of both adiabatic and non-adiabatic processes near the acoustic source. Broadband acoustic fluctuations are shown to be significantly less than the narrowband fluctuations. Variations in the complex pressure phase and amplitude are discussed. Intensity statistics, such as scintillation index and the probability distribution function, are discussed as a function of depth and time for narrowband and broadband (replica correlation) processing.

Keywords

Physics, Acoustics

Link to Full Text

http://access.library.miami.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3008180