Fluctuations of high‐frequency acoustic pulses in shallow water

Abstract

High‐frequency acoustic propagation and scattering experiments were conducted near Panama City, FL, in August of 1991 and 1993, and in Eckernforde Bay, Germany in May 1993. The Panama City site has a hard sand bottom, but the bottom of Eckernforde Bay is soft mud. Environmental measurements were made in conjunction with acoustic measurements. The water depth at both sites was approximately 30 m. The sources and the receiver arrays were mounted 6 to 8 m from the bottom and were separated by about 90 m. A bottom reflected signal was detected in Panama City, and in some cases, in Germany. The soft mud bottom of Eckernforde Bay, however, absorbed most of the energy directed toward it. Data from pulses 1.0 ms in length, at 1‐s intervals, will be shown for frequencies from 20 to 180 kHz. Means, standard deviations, and coefficients of variation of 100 or 150 pulses for each frequency characterize two scales of temporal variability in the data. Data from several of the receiving hydrophones are compared. Spatial variability is shown and related to modeled and measured changes in the sound velocity profile. [Work supported by the Office of Naval Research.]