Ambient noise and source tracking in very shallow water

This paper will describe recent experiments on ambient noise levels and source tracking in shallow water. The measurements were made using a sparse acoustic array in approximately 20 m deep water at a location just south of the Port Everglades inlet. The ambient noise was dominated by local boat traffic events and was found to be very intermittent especially during daylight hours. Between events the noise was dominated by biological activity inshore of the array. It will be shown that the most important issue that adversely affects the acoustic tracking of AUVs is boat traffic noise. It was found that tracking accuracy at larger ranges is good, but the results are more inconsistent due to lower received signal levels. The algorithm used in this analysis was not necessarily optimized for noise rejection, but the results clearly indicate that signal fading and signal to noise are the main problems that have to be addressed to improve tracking performance. [Work supported by ONR.]