High-Frequency Broadband Seafloor Backscatter in a Sandy Estuarine Environment

Eric J. Bajor
M.S. Thesis Defense

Mechanical Engineering

Monday, Jun. 1, 2015, 11:00am
Chase 130
Abstract

Seafloor backscatter collected with high-frequency (> 100 kHz) hydrographic echosounders has become an important aspect of seafloor characterization for benthic ecologists and other scientists. The mechanisms that control acoustic scattering at these high frequencies are not completely understood, although surficial roughness and the presence of discrete inclusions (e.g., shell hash) are likely contributors. To further our understanding of the impact these mechanisms have on seafloor scattering, broadband (100-250 kHz) acoustic measurements were taken at a grazing angle of 45° in a shallow-water, sandy environment with a known presence of shell hash.  Stereo imagery was collected simultaneously to quantify the roughness spectrum of the seafloor. Sediment samples were also collected on site of the experiment to quantitatively analyze the content of shell hash. Frequency dependence of backscatter appeared weak for frequencies between 180 kHz to 250 kHz and more dominant at frequencies between 100 kHz to 150 kHz. Data to model comparisons of the frequency dependence of seafloor backscatter were made to both roughness and discrete inclusion scattering models indicating neither model as a good descriptor of the seafloor backscatter response.

Bio

Eric Bajor completed his Bachelor of Science in Mechanical Engineering at the University of New Hampshire in May 2013. He began work at CCOM shortly after graduation and became involved with the Newbex project. His interests of research include underwater acoustics and fluid dynamics.