Design and Field Experiment of the Coastal Acoustic Tomography

The coastal acoustic tomography (CAT) system was developed to measure currents in the coastal water with heavy shipping traffic and fishing activities. The CAT system was designed for transmitting and receiving the sound signal at same time, and accurate measuring acoustic travel time between two separated stations by using the M-sequence sound signal and GPS clock. The operating frequency of CAT system was 3-7.5 kHz, and the accuracy of clock was 0.5 mus. A reciprocal sound transmission experiment was carried out in a shallow river, using a 5 kHz M sequence of 9th order. The sound signals were successful received at two stations with a mean signal to noise ratio of about 83 and 71. The field experiment indicated that the CAT system operated correctly.