Long-term measurements of high-frequency scattering from the seafloor

Abstract

The assumption often used for predicting the performance of many sonar systems is that the acoustic response of the seafloor is solely a function of seabed type and that this response has no temporal dependence. However, seafloor properties controlling acoustic scattered levels and statistics are variable as they are influenced by near-bottom hydrodynamics and/or biological activity. Variability in seafloor acoustic scattering can significantly increase uncertainty in predictions of the performance of object-detection and classification sonar systems as well as seabed-characterization systems. Using several datasets obtained during a series of experiments utilizing 38, 70, and 200 kHz transducers, variability in scattered levels over temporal scales of weeks to months was measured at two sites near Portsmouth, New Hampshire, USA. Results from these experiments will be discussed along with the mechanisms causing variability in scattering strength at the two sites and potential for modeling this temporal variability.