Effects of internal waves on sound propagation in the shallow waters of the continental shelves

Abstract

Sound waves propagating through the oceans are refracted by internal waves. In the shallow waters of the continental shelves, an additional downward refraction of sound waves due to internal waves can cause them to interact more often with the seabed, resulting in additional energy from the sound waves being dissipated into the seabed. This study investigates how internal waves affect sound propagation on the continental shelves. It first quantified the types of internal waves on the continental shelf of California, near Point Sal, using data collected from a field experiment. Next, the effects that these internal waves have on sound propagation were quantified via simulations using a ray theory acoustic model. The results showed that internal waves in the experiment area were largely generated by tidal forcing. Compared to simulations without internal waves, simulations accounting for the effects of internal waves resulted in higher sound energy loss, as internal waves tend to cause sound waves to strike the seabed at steeper angles and over shorter distances. Thus, to enable a more accurate assessment of underwater acoustic system performance, the effects of internal waves on sound propagation in shallow waters need to be accounted for.