The normal‐mode theory of air‐to‐water sound transmission in the ocean

The normal‐mode theory is presented for the transmission of sound from a stationary source in a homogeneous, stationary, air layer into an arbitrarily stratified ocean. Transmission loss calculations are performed for a Pekeris‐type shallow‐water environment consisting of an isospeed water layer over a uniform elastic solid seabed. Notable features of the results are: the sensitivity of transmission loss to bottom type, the weak dependence of incoherent transmission loss upon source height, and a 25 log r range dependence of average transmission loss in the mode‐stripping region. Finally, some approximate intensity‐range relations are proposed for shallow‐water propagation.