Underwater Acoustic Detection and Signal （水声探测和信号）.pdf

12 Underwater Acoustic Detection and Signal Processing Near the Seabed Henry M. Manik Department of Marine Science and Technology Faculty of Fisheries and Marine Sciences, Bogor Agricultural University Kampus IPB Darmaga Bogor 16680 Indonesia 1. Introduction 1.1 Background Underwater acoustic instruments has been an indispensable tool to study the ocean. Echo sounder is one of the acoustic instrument used to remotely classify distributions of biological organisms such as fish and plankton (MacLennan and Simmonds, 1992; Furusawa, 2000). Knowledge of species, location, and behavior observed by the sounders are important for fisheries, fisheries management, and ecological studies. Echo sounders have also been used to characterize the sea bottom type such as rocks, sand, and mud (Stanton, 1994). The characterization of the sea bottom type are useful in applications such as fish habitat study, fishing port construction, geological studies, marine exploration, and mining. With the end of World War II, studies on underwater acoustics for sea bottom interactions began extensively. Urick (1954) defined the measure of backscatter strength as the ratio of scattered energy to incident energy per unit area, per unit solid angle and this quantity was expressed in decibels. Urick used the frequencies of 10 to 60 kHz to measure the backscattering from the harbor bottom. Mackenzie (1961) published the results