DETECTION OF SONAR INDUCED MEASUREMENT UNCERTAINTIES IN ENVIRONMENTAL SENSING: A CASE STUDY WITH THE TOROIDAL VOLUME SEARCH SONAR

摘要

Shallow water field measurements of ocean volume and boundary acoustic backscatter, made with the US Navy's 68 kHz Toroidal Volume Search Sonar (TVSS), are used to demonstrate the benefits and side effects of a synoptic 360° vertical viewing field with 120 beams at 3° increments when investigating the spatial and temporal variability of the environment. Boundary backscatter measurements can help identify and quantify uncertainties introduced by the sonar system, thus setting realistic bounds on the spatial and temporal scales of environmental features that can be detected with this multibeam sonar. However, acoustic energy reflected at the boundaries and received in the vertical sidelobes of beams steered in the ocean volume often masks finer volume acoustic reverberation features from scattering layers of zooplankton or resonant micro-bubbles. In such cases, a 3 dimensional image built from a sequence of pings along the sonar's track has proven effective in discriminating sonar induced apparent acoustic variability from environmental variability. A multisector and multi-frequency transmission scheme is proposed to minimize boundary sidelobe interferences.