Depatrment of Marine Science and Technology, Tokyo University of Fisheries, Minato, Tokyo 108-8477, Japan
A method for evaluating and designing acoustic systems for ultrasonic biotelemetry for investigating fish behavior is developed. The objective of the method is to surely receive the signal from a pinger by increasing the signal-to-noise ratio (SNR) and widening the detectable range. First, the SNR is derived as a function of source pressure of the pinger, sound traveling characteristics, receiving directivity, and noise level. Based on the SNR, the detectable beam width is defined as a new concept and the indices that describe the maximum detectable range and the detectable beam width are introduced. A universal diagram for the basic design of the biotelemetry system where SNR is plotted against frequency is developed. An appropriate frequency, receiving transducer diameter, detectable beam width, and number of receiving transducers are easily determined by using the diagram.