Transmission loss in the Yellow Sea: Data interpretations and model comparisons

Abstract

The Yellow Sea represents a natural laboratory for the study of shallow water acoustic propagation as influenced by a strong summer thermocline, energetic internal wave fields, and a seabed considered relatively range independent. In this paper results of transmission loss measurements obtained in the Yellow Sea, during the joint China-U.S. Yellow Sea ’96 experiment, conducted in August 1996 are presented. Explosive sources were deployed at ranges 1–30 km, and acoustic data were recorded on a vertical array that spanned the entire water column depth of ∼75 m. The data are in 1/3-octave bands with center frequencies 70 to 700 Hz. A simple geoacoustic model is derived for the seabed that shows consistency with data at ranges of O(1 km), where raylike properties are exhibited, and of O(10 km), where modelike properties are exhibited. With summer conditions prevailing, the sound speed profile was described by two isovelocity layers linked by a layer with a linear gradient. Internal tide activity modulated the depth of the linear gradient layer over the course of the experiment, and this effect is also examined using various modeling approaches.