On the use of broadband acoustic scattering techniques for observing physical and biological scattering features in the ocean.

Abstract

Broadband acoustic scattering techniques, and associated signal processing techniques, are emerging as a powerful tool for the remote sensing of physical and biological scattering features in the ocean. These techniques allow (1) the frequency spectrum of oceanic scatterers to be measured, thereby resulting in enhanced classification and quantification potential relative to more traditional single‐frequency scattering techniques, and (2) increased spatial resolution resulting in high‐resolution images of oceanic scattering features, obtained through use of pulse compression signal processing techniques that exploit the broadband content of the signal. In this presentation, broadband processing techniques are discussed and results from laboratory and field measurements of broadband acoustic scattering from both physical and biological scatterers, spanning the frequency range from 100–600 kHz, are presented. Controlled laboratory broadband scattering measurements allow coherent ping‐to‐ping analysis to be performed as well as individual scattering features to be determined. The laboratory approaches are then expanded into the field to investigate physical and biological scattering features in the ocean on relevant temporal and spatial scales. Examples of broadband field measurements are presented from recent field experiments, and include scattering from nonlinear internal waves, zooplankton, turbulent oceanic microstructure, salinity microstructure in rivers, and bubbles.