Measurement of down‐slope sound propagation from a shallow source to a deep ocean receiver

An experiment has been performed to investigate the coupling of surface–ship noise to the deep ocean sound channel. These calibrated measurements of sound propagation from the 18‐m, 135‐Hz source were obtained at a deep ocean receiver while the source tow proceeded from deep water up the Sable Island Bank at ranges between 730 and 910 km. The sound propagation path was from the cold slope waters over the bank through the Gulf Stream and to the edge of the Sargasso Sea. The mean value of the transmission loss was 110 dB with a down‐slope enhancement estimated to be 4 dB resulting from the combined effects of trapping in the strong shallow sound channel and reflections from the slope. Comparisons with calculated results using the parabolic equation method were good and demonstrate coupling to the deep ocean sound channel. The acoustic field, sampled by 16 transverse hydrophone groups with a 4.75‐m center spacing over six consecutive (12.5 s, 0.08 Hz) samples, yielded a mean standard deviation of 1.7 dB (6≤S...