Analytical sonar detector is an electronic device that uses underwater sound waves to detect, locate and communicate underwater targets. It is the most widely used and important device in hydroacoustics. Sonar can be divided into active sonar and passive sonar according to its working mode. ① Active sonar: Active sonar technology means that sonar actively emits sound waves to "illuminate" the target, and then receives the echo reflected by the underwater target to determine the parameters of the target; (2) Passive sonar: Passive sonar technology means that sonar passively receives radiated noise generated by underwater targets such as ships and signals sent by underwater acoustic equipment to determine the direction of the targets.