Bill Diedrich: Do fish hear sonar signals?

This is a common question asked at sport shows and seminars. Many tests have been conducted and the answer is no, at least for freshwater fish and equipment. Here are the hearing-range frequencies for the relevant groups. Most fish have a hearing range of 1 Hz to 1 kHz, humans from 10 Hz to 20 kHz. Most freshwater sonar operates from 50 kHz to 400 kHz. Humans might hear the transmit pulse that sounds like a click from the transducer.