Analysis of low-frequency, broadband measured reverberation levels at Blake Escarpment

Abstract

Acoustic reverberation data were acquired at the Blake Escarpment using Naval Research Laboratory’s (NRL’s) deep towed acoustic/geophysics system (DTAGS). DTAGS is similar to a seismic acquisition streamer system with its own omnidirectional source (LFM, from 250 to 650 Hz) but consists of two collinear receiver arrays (an acoustic and a geophysics) and can be towed in deep waters (to 5000 m). Although DTAGS acquires acoustic and geophysics data simultaneously, only the acoustic array data are analyzed here. The acoustic (field) data consist of backscattered reverberations and/or specular reflection events from all angles. These data are first transformed into p-t (ray-parameter versus time-intercept) domain and studied to retain the grazing angles (intermediate and high) of interest. These selected angles of interest are further analyzed to determine the reverberations versus frequency relationships, and also transformed back to space-time domain to determine the locations of the scattering patches that produced the reverberations. [Work supported by ONR, ARSRP Program.]