RESEARCH PROGRAM IN ACOUSTIC REVERBERATION.

In experiments in the Straits of Juan de Fuca, north of Seattle, Washington, sequential reverberation records were produced using pulsed continuous wave signals and a vertically-oriented, bottom-mounted, narrow-beam transducer. Several-hundred-pulse sequences were transmitted on the hour for 250 consecutive hours. The resulting reverberation was demodulated in quadrature and recorded on analog tape. The tapes were returned to the laboratory and digitized. Estimates of data parameters were then obtained using ensemble averaging techniques and the behavior of the estimates as a function of time was studied. Special attention was given to the determination of probability density functions, detection of environmental nonstationarity by testing the data for statistical inhomogeneity, and isolation of spatial-temporal patterns in the volume back-scattering strengths. Volume scattering strengths for the whole 250-hour period were obtained as a by-product of the latter activity. Diurnal variations as well as higher frequency space-time changes are clearly indicated. Author