50 kHz bottom backscattering measurements from two types of artificially roughened sandy bottoms

Abstract

Laboratory measurements of 50 kHz bottom backscattering strengths as a function of grazing angle were performed on the sandy bottom of a water tank; two types of bottom roughnesses, a relatively smooth interface and a rough interface, were created on the bottom surface. The roughness profiles of the two interface types were measured directly using an ultrasound arrival time difference of 5MHz and then were Fourier transformed to obtain the roughness power spectra. The measured backscattering strengths increased from -29 to 0 dB with increasing grazing angle from 35 to 86 degrees, which were compared to theoretical backscattering model predictions. The comparison results implied that bottom roughness is a key factor in accurately predicting bottom scattering for a sandy bottom. (C) 2016 The Japan Society of Applied Physics