Measurements of high frequency acoustic transmission loss during SAVEX15

Abstract

Transmission loss measurements in high frequency range along with the ocean environmental measurements were made during the Shallow-water Acoustic Variability EXperiment 2015 (SAVEX15) in the south of Jeju Island, Korea, where the water depth is about 100 m. Two vertical line arrays (VLAs) were moored with a distance of 5.5 km, covering the water column between 24 and 80 m. Continuous waves in a frequency band of 10-25 kHz were transmitted from a vertical source array at depths of 30-45 m. Sound speed and temperature profiles were measured using a standard/stationary conductivity-temperature-depth (CTD), underway CTD, and temperature loggers attached to the two VLAs. The measured sound speed profiles consistently reveal a sound speed minimum layer (SSML) at depths between 30 to 50 m. During the SAVEX15 period, the perturbations in the SSML derived by various kinds of internal waves were observed. In this talk, the temporal fluctuations of the measured transmission loss are presented, and the results are discussed in comparison with the internal wave field in the region. [Work supported by ONR, KIOST, SNU, and ADD.]