Broadband and statistical characterization of echoes from random scatterers : application to acoustic scattering by marine organisms
MetadataShow full item record
The interpretation of echoes collected by active remote-sensing systems, such as sonar and radar, is often ambiguous due to the complexities in the scattering processes involving the scatterers, the environment, and the sensing system. This thesis addresses this challenge using a combination of laboratory and fi eld experiments, theoretical modeling, and numerical simulations in the context of acoustic scattering by marine organisms. The unifying themes of the thesis are 1) quantitative characterization of the spectral, temporal, and statistical features derived from echoes collected using both broadband and narrowband signals, and 2) the interpretation of echoes by establishing explicit links between echo features and the sources of scattering through physics principles. This physics-based approach is distinct from the subjective descriptions and empirical methods employed in most conventional fisheries acoustic studies. The fi rst part focuses on understanding the dominant backscattering mechanisms of live squid as a function of orientation. The study provides the first broadband backscattering laboratory data set from live squid at all angles of orientation, and conclusively con firms the fluidlike, weakly-scattering material properties of squid through a series of detailed comparisons between data and predictions given by models derived based on the distorted-wave Born approximation. In the second part, an exact analytical narrowband model and a numerical broadband model are developed based on physics principles to describe the probability density function of the amplitudes of echo envelopes (echo pdf) of arbitrary aggregations of scatterers. The narrowband echo pdf model signi cantly outperforms the conventional mixture models in analyzing simulated mixed assemblages. When applied to analyze fish echoes collected in the ocean, the numerical density of sh estimated using the broadband echo pdf model is comparable to the density estimated using echo integration methods. These results demonstrate the power of the physics-based approach and give a rst-order assessment of the performance of echo statistics methods in echo interpretation. The new data, models, and approaches provided here are important for advancing the eld of active acoustic observation of the ocean.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2013
Suggested CitationThesis: Lee, Wu-Jung, "Broadband and statistical characterization of echoes from random scatterers : application to acoustic scattering by marine organisms", 2013-02, DOI:10.1575/1912/5823, https://hdl.handle.net/1912/5823
Showing items related by title, author, creator and subject.
Quantification of the spatial and temporal evolution of stratified shear instabilities at high Reynolds number using quantitative acoustic scattering techniques Fincke, Jonathan R. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2015-02)The spatial and temporal evolution of stratified shear instabilities is quantified in a highly stratified and energetic estuary. The measurements are made using high-resolution acoustic backscatter from an array composed ...
Acoustic scattering from sand dollars (Dendraster excentricus) : modeling as high aspect ratio oblate objects and comparison to experiment Dietzen, Gregory C. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2008-09)Benthic shells can contribute greatly to the scattering variability of the ocean bottom, particularly at low grazing angles. Among the effects of shell aggregates are increased scattering strength and potential subcritical ...
Characterization of underwater target geometry from Autonomous Underwater Vehicle sampling of bistatic acoustic scattered fields Fischell, Erin M. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2015-06)One of the long term goals of Autonomous Underwater Vehicle (AUV) minehunting is to have multiple inexpensive AUVs in a harbor autonomously classify hazards. Existing acoustic methods for target classification using ...