Prediction of ping-to-ping cross talk in fisheries sonar

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.]