Acoustic normal mode dispersion in shallow water with a low speed bottom layer

Abstract

Acoustic propagation in shallow water is greatly influenced by the properties of the sea bottom. Most of the continental shelf regions of the world have a surficial sediment layer consisting of granular materials such as sand and silt. This is especially true for the east coast of the United States. There has been significant amount of research conducted over the past decades understanding the acoustic properties (compressional and shear wave speeds and attenuations) of these sediments and its impact on acoustic propagation. Compared to granular (sandy) sediments, much less is known about the acoustics of fine-grained sediments such as clay and mud. There has been limited studies undertaken in the past to understand the impact of a low velocity surficial sediment layer on acoustic propagation. This study demonstrates the possibility of trapped modes in the surficial soft sediment layer based on model results. Effect of some of the environmental parameters such as the changes in the sound speed in water, thickness of mud layer, changes in the sound speed in the acoustic basement is investigated.