Normal‐mode propagation in deep‐ocean sediment channels

Abstract

E. L. Hamilton has discussed the likelihood of ducted acoustic transmission in deep‐ocean sediment channels, just below the water‐bottom interface. The normal‐mode solution is presented here; it yields eigenfunctions, the associated eigenvalue equation, and the minimum acoustic frequency that allows trapping of any specified mode. This frequency increases nearly linearly with mode number. Much of the acoustic energy propagated by any trapped mode travels through lossy bottom sediment. Accordingly, equations are derived for the attenuation coefficient of the nth mode. Numerical results are given for an “average” channel at a frequency of 100 Hz. [This work was sponsored by Naval Electronic Systems Command and Naval Ocean Research and Development Activity.]