Measurement of acoustic backscattering from rocky outcrops in Monterey Bay

Abstract

Acoustic scattering is an interaction between acoustic waves and inhomogeneities (interface or volume) which results in acoustic energy being dispersed in all directions. Scattering strength, a measure of the incoherent scattered energy, depends on grazing angle, frequency, bottom roughness, and/or sediment type and can be a source of false alarms for target detection systems. Understanding acoustic backscatter relationships of the sea floor allows for remote sensing applications, as well as target detection performance, in these areas. Acoustic backscatter from sand and mud bottoms has been studied extensively, but only six rocky bottom studies have been performed to date, motivating our study of high frequency acoustic scattering from rocky environments. For this project, acoustic data were collected and analyzed to measure the acoustic backscattering strength of rocky seafloors as a function of grazing angle, bottom roughness, and frequency in Monterey Bay, CA. High-frequency acoustic surveys with two narrowband split-beam echosounders, 200 kHz and 420 kHz, were conducted. Backscatter measurements were compared to existing bathymetric and geologic surveys from California State University, Monterey Bay and the California Geologic Survey to qualitatively compare backscattering strength to roughness features and geology.Acoustic scattering is an interaction between acoustic waves and inhomogeneities (interface or volume) which results in acoustic energy being dispersed in all directions. Scattering strength, a measure of the incoherent scattered energy, depends on grazing angle, frequency, bottom roughness, and/or sediment type and can be a source of false alarms for target detection systems. Understanding acoustic backscatter relationships of the sea floor allows for remote sensing applications, as well as target detection performance, in these areas. Acoustic backscatter from sand and mud bottoms has been studied extensively, but only six rocky bottom studies have been performed to date, motivating our study of high frequency acoustic scattering from rocky environments. For this project, acoustic data were collected and analyzed to measure the acoustic backscattering strength of rocky seafloors as a function of grazing angle, bottom roughness, and frequency in Monterey Bay, CA. High-frequency acoustic surveys with two ...