Calibration of an acoustic echo-integration system in a deep tank, with system gain comparisons over standard sphere material, water temperature and time

This paper outlines the theory and procedures for calibrating an echo integration acoustic system with a standard sphere. It presents the results of an extensive calibration of a Simrad EK500 scientific echo sounder with a 120 kHz sprit-beam transducer in a refrigerated 10m deep tank. Calibration parameters are studied in relation to sphere material (WC and Cu), water temperature (0.5-5.5°C), transmitted pulse length (0.1, 0.3, and 1.0 ms), target depth (0.8 - 7.5 m), and time (149 days). A discussion follows concerning the ramifications of calibration errors and variability on the accuracy of acoustic biomass estimation.