Quantifying the spatial variability of low frequency acoustic propagation in the Northern East China Sea

Abstract

During a period 14-28 May, 2015, the Shallow-water Acoustic Variability EXperiment 2015(SAVEX15) was made in the northern East China Sea (ECS) to obtain acoustic and oceanographic data for studying the coupling of physical and geophysical parameters, which could affect the variability of acoustic propagation. A strong underwater sound channel (USC) had been existed at depths ranging from 30 to 50 m with channel axis at ~40 m during the SAVEX15 period. Two types of mid-range propagation measurements were conducted in shallow water (nominal water depth of ~100 m) using simultaneously both continuous waves superimposed at several fixed frequencies below 1.6 kHz and impulsive broadband signals transmitted by sparker system. A vertical line array composed of temperature and pressure sensors was moored for measuring the acoustic signals and vertical soundspeed profiles in time. And a marine geophysical survey using a chirp sonar, sparker system, and sediment cores conducted at the experimental site showed that there was a thin surficial layer of O(1 m) overlaying multiple layers under the water-seabed interface. The measurement results of transmission loss are presented and compared to the model predictions using the measured oceanographic data. parameters, which could affect the variability of acoustic propagation. A strong underwater sound channel (USC) had been existed at depths ranging from 30 to 50 m with channel axis at ~40 m during the SAVEX15 period. Two types of mid-range propagation measurements were conducted in shallow water (nominal water depth of ~100 m) using simultaneously both continuous waves superimposed at several fixed frequencies below 1.6 kHz and impulsive broadband signals transmitted by sparker system. A vertical line array composed of temperature and pressure sensors was moored for measuring the acoustic signals and vertical soundspeed profiles in time. And a marine geophysical survey using a chirp sonar, sparker system, and sediment cores conducted at the experimental site showed that there was a thin surficial layer of O(1 m) overlaying multiple layers under the water-seabed interface. The measurement results of transmission loss are presented and compared to the model predictions using the measured oceanographic data.