Acoustic current measurement using travel-time method in Bachimen Harbor, Taiwan

A reciprocal acoustic transmission experiment was conducted in Bachimen Harbor, Keelung on December 4, 2009. Sound pulses were transmitted reciprocally between two Coastal Acoustic Tomography Systems (CATs) placed on the North bank and separated by 490 m. The received pulse responses show two dominant ray groups. Using horizontal ray simulation from the BELLHOP ray tracing program, the two arrival groups were identified as the direct rays and the horizontally reflected rays reflected from the North bank. Two methods were used to obtain the differential travel times: peak-picking and waveform-matching methods. In general, the results from the reciprocal transmission data were in good agreement with the measurement of Horizontal Acoustic Doppler Current Profiler (HADCP). The results suggest that reciprocal sound transmission is applicable to current reconstruction in the harbor sea.