Modeling and analysis of sound transmission in the Strait of Korea

The experiment called the Acoustic Characterization Test III was performed in the oceanographically complex Strait of Korea. It was designed to provide accurate measurements of sound transmission and array signal gain under known environmental conditions. Bottom sampling and sub-bottom surveys coupled with archival geophysical information provided the basis for the geoacoustic depth profiles of sound speed, density and attenuation. The bottom was a sand-silt sediment for which shear wave propagation at experimental frequencies was determined to be unimportant. Using the compressional wave profiles, the measured bathymetry and the water sound speed as input parameters, good agreement was obtained between measured and calculated narrowband transmission loss when an attenuation profile with a frequency dependence to the 1.8 power in the near sediment-water interface layer was used. This power law was determined by using an effective attenuation coefficient and a least squares comparison of calculated and measured sound transmission of five narrowband tones between 47 and 604 Hz. The resulting geoacoustic model was used to compare measured and calculated broadband sound transmission and signal spread and excellent agreement was found. These results are consistent with measurements in other sand-silt areas where site specific frequency dependent characteristics have been observed