ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

2aUW3. Measurements and interpretation of spatial coherence and angular spread resulting from multiple boundary interactions in a shallow-water channel.

Peter H. Dahl

Warren L. J. Fox

Appl. Phys. Lab., Univ. of Washington, Seattle, WA 98195

Measurements of the spatial coherence of high-frequency [0(10 kHz)] sound having propagated in a shallow-water channel are discussed. The experiment was conducted near Key West, Florida, in water depth of approximately 25 m. The bottom consisted of calcium shell deposits and soft mud. Measurements were made using omnidirectional sources suspended from a spar buoy and a horizontal line array of receivers. Broadband pulses were used in order to resolve the separate arrivals, e.g., direct path, single-surface, and double-surface bounce paths. With each boundary interaction, either surface or bottom, the forward propagating energy is scattered further in angle. The transmissions were measured along a line array oriented transverse to the direction of propagation, thereby giving an estimate of the horizontal coherence or equivalent horizontal angular spread. The results are discussed in the context of key geometric parameters such as source/receiver depth and range, and environmental parameters such as wind speed and surface wave spectral characteristics. [Work supported by ONR.]