A Synopsis of Studies on the Interaction of Low Frequency Acoustic Signals with the Ocean Bottom.

摘要

Understanding the mechanisms by which the ocean sediment redirects impinging sound back into the ocean is necessary in developing propagation models for SONAR performance prediction. Thus, NUSC has (1) conducted controlled, self-calibrating acoustic measurements where the bottom interacted signal is isolated in time for analysis, (2) developed deconvolution processing techniques to aid in describing the impulse response of the ocean sediment and (3) performed modeling to study the interaction of acoustic waves at the ocean bottom. This document presents a synopsis of the studies primarily showing the necessity to consider the refraction of sound by the ocean sediment when predicting low frequency propagation loss. Sediment refraction of sound and reflection of sound by the sediment interface and subbottom layering are the causes for the negative bottom loss phenomenon and for a given frequency bandwidth dependence and receiver depth dependence of bottom loss. Deconvolution analyses have aided in time resolution of intrapulse signals that make up the bottom interacting arrivals. Resolution of these arrivals aids in interpreting results. The FFP modeling effort provides quantitative evidence for the necessity to consider the refraction of sound by the ocean sediment to properly interpret low frequency propagation loss measurements in areas where the ocean bottom plays an important part. (Author)