Estimation of Ocean and Seabed Parameters and Processes Using Low Frequency Acoustic Signals

Abstract

The long term goals of our research are to: • Understand, model and exploit the acoustic propagation physics in shallow water in the presence of ocean fronts and internal waves. This goal conforms to the major theme of the Shallow Water 06 experiment i.e. 3-D acoustic effects. The effects of oceanographic variability such as frontal meander, and internal solitary waves on 3-D acoustic reflection and refraction will be investigated. • Improve inversion schemes for the estimation of sediment geoacoustic properties using low frequency broadband acoustic signals. The existing inversion method has been shown to successfully map compressional wave speed. The new work will focus on understanding the frequency and depth dependence of compressional wave attenuation and develop new inversion schemes for shear wave properties. We hypothesize that water-borne acoustic arrival properties such as their Airy Phase are sensitive to sediment shear properties. OBJECTIVES We are proposing to address our goals with a series of objectives: A. Characterize 3-D acoustic variability due to internal waves and fronts. The tasks associated with this objective are: 1. Data analysis: Acoustic signals transmitted from the R/V Sharp in the Shallow Water 06 Experiment at various ranges and angles to the WHOI Shark Array and Single Hydrophone Receive Units (SHRU) will be analyzed. 2. Calculate various intensity metrics: Different intensity metrics will be calculated, including scintillation Index (SI), integrated energy over the depth of the array and over the duration of the acoustic signal, temporally integrated energy over the duration of the acoustic signal on a single hydrophone, single hydrophone intensity observations.