Acoustic phase stability in a shallow-water environment

Abstract

The formation of a synthetic aperture is dependent on the phase stability of the medium. Temporal and spatial phase stability of the medium were estimated from measurements taken during a high-frequency experiment conducted in August 1993 in the shallow-water coastal environment off Panama City, Florida. Phase stability was estimated from sequences of 150 0.5-ms and 1.0-ms pulses separated by 1-s intervals at experimental frequencies of 20, 40, 60, and 90 kHz. Phase fluctuations were found to contain both deterministic and random components which changed with time, indicating a changing propagation environment. Phase fluctuations were spatially correlated between both vertical and horizontal components of the receiving array. The relationship between acoustic phase stability and environmental factors is examined. Results of this analysis are compared with previous phase stability measurements [J. T. Christoff, C. D. Loggins, and E. L. Pipkin, J. Acoust. Soc. Am. 71, 1606–1607 (1982); P. T. Gough and M. P. Hayes, ibid. 86, 837–839 (1989)]. [Work sponsored by ONR.]