Guided acoustic waves in the ocean

Abstract

Reviews the development of the theory and experiment for deep and shallow water since 1963. Theoretical approaches use rays, modes and a wide variety of other concepts. The classic case has a constant depth profile of sound velocity, but for long ranges one must allow for profiles varying both with range and with the transverse direction. Experimentally the transmission in deep water can be very good, especially for low frequencies in the SOFAR channel, where what little attenuation there is has been demonstrated to arise from a boron relaxation process. For shallow water the largest uncertainties at low frequencies can come from the unknown nature of the bottom structure. The study of variability has been helped by the existence of fixed sites, showing the occurrence of fluctuations with a great variety of mechanisms and time scales. For most of these the key is multipath interference, e.g. this comes into the acoustic effects of internal waves in the deep sea, and also into the spatial variability in deep channels.