Transverse Coherence of Low-Frequency Acoustic Signals.

Results are reported for a long-range deep-ocean experiment in which a 15-Hz CW source was towed transverse to the line of propagation to a single receiver. Reciprocity between transmitter and receiver roles is used to interpret the aperture formed by the moving source as a large receiving aperture. For the shallow source and bottom-suspended SOFAR-axial receiver employed, we observed the largest physical broadside apertures yet reported over which the received signal was coherent. The maximum observed coherent interval corresponds to a broadside aperture of 14 km at 1600 km range. The measured array gain for this aperture was 1.2 dB less than the maximum possible. (Author)