Abstract:
Faster ping rates in fish assessment sonars yield higher spatial resolution information, and can reduce the variance of the target strength estimate by taking multiple measurements on single targets [J. E. Ehrenberg and T. C. Torkelson, ICES J. Mar. Sci. 53, 329--334 (1996)]. However, an effect of this corresponding shorter trigger interval is a decrease in spreading time, causing a reduction of spreading loss from the previous ping such that false echoes can result in deep water if the ping rate is too high. This ping-to-ping cross talk is a function of the ping rate, bottom depth and type, applied TVG, and sound absorption. A method has been developed which estimates the energy loss from a previous ping based on those variables, thus allowing one to establish a maximum ping rate for a desired echo-integration threshold. Deep-water measurements of ping-to-ping cross talk were then taken to validate this method. [Work supported by EVOSTC.]