default Effects of the internal waves on the acoustic propagation

By In Memorandum Reports

Effects of the internal waves on the acoustic propagation. SM-433. July 2005.

A simple 2D model called SOFIA has been developed in order to predict sound-speed fluctuations in the water column due to linear internal waves. It is based on solving the equation governing the vertical particle velocity associated with the internal waves, using a modal decomposition of the internal wave field. The main feature of the model is the use of experimental data: the Brunt-Väisälä profile is calculated from the density profile registered by the CTD cast, the amplitudes of the normal modes are determined using ADCP data and the spectrum is deduced from the thermistor chain measurements. The effects of the linear internal waves on the acoustic propagation were studied through several numerical simulations using some sound-speed profiles predicted with the SOFIA model. The acoustic simulations were performed with the REVPA model, based on a wide-angle approximation of the parabolic equation (PE) method. Through these simulations, the possible relation between the influence of the internal waves and different values of the environmental parameters was assessed. The environmental parameters considered in this study were the source depth, the acoustic frequency and the sediment properties.