Abstract
A method to measure noise at the output of echo integrators has been developed for precise estimation of fisheries resources by acoustic means. This method is more practical than the method to measure noise at receiver output, because noise contribution can be easily compared withthe volume backscat-tering strength (SV) of fish and because there is less ambiguity in noise measurement. Also a conversion equation of the echo integrator output to the equivalent noise spectrum level isderived. This facilitates the comparison, for example, between different echo sounding system.We applied this method to a dual beam echo sounding system on board research vessel Kaiyo-maru, and confirmed that the difference in noise SV of 5 dB agreed with the theoretical prediction.
