Modeling the effects of sediments on the acoustic response of buried elastic cylinders to low-frequency broadband signals.

Abstract

Low-frequency broadband (LFBB) sonars have the advantage of penetration into the sea-floor, thus allowing ensonification of buried targets, but the disadvantage of inferior spatial resolution. Hence, this technology heavily relies on reducing false alarms through recognition of details of the acoustic signature. This reports on an effort to characterize the changes in the acoustic signatures that occur for elastic cylinders buried in various sediments. Numerical modeling of both target and reverberation highlight several difficulties in detection and classification of buried targets, most notably reduced signal excess for targets in sands and larger grain size sediments. Moreover, practical limits on sources and receivers limit the usable bandwidth of LFBB systems, consequently restricting the observable information used for characterizing the acoustic response of targets. Time-frequency analysis methods of modeled signals reveal little information that distinguishes a signal of interest from a rigid or point scatterer (potential false targets).