Observations of the phase and amplitude of individual Fermat paths in a multipath environment

FM slide and pulsed‐tone signals at 2, 4, 8, and 16 kHz were transmitted from a source to a receiver at the same depth 1100 m distant. Three wholly refracted paths were observed in the return signals, and a discussion of the six‐hour time series of the arrival times and amplitudes for each path is presented. Evidence is given of acoustic frequency‐dependent scattering, and scattering from oceanic fine structure is suggested as the most likely physical mechanism to explain the observations.