Abstract:

It is well known that the acoustic field propagated through a shallow- water waveguide is sensitive to the properties of the waveguide and its boundaries. Through adiabatic mode theory, it is understood that the modal eigenfunctions and eigenvalues adapt to the local environment and changing boundary conditions. It has been proposed that modal tracking may be employed in a laterally varying waveguide to infer properties of the normal-mode field and the environment. In support of a three-dimensional modal mapping experiment, synthetic three-dimensional acoustic fields are generated to simulate propagation in a shallow-water region in the vicinity of the East Coast strataform site. Synthetic fields are computed using normal-mode and parabolic equation codes and transformed to the wavenumber domain to obtain estimates of the spatially varying spectral content of the modal field. The resulting modal maps are discussed for several experimental regions. [Work supported by ONR and ARL Penn State Univ.]