Researches On The Active-passive Acoustic Characteristics And The Method Of Detection Of The Underwater Diver

Underwater diver has been an important threat to the targets such as: port, dock and some military facilities. The research of acoustic characteristics from diver is critically important for the early warning of diver. This paper studies the acoustic characteristics of diver, provides the theoretical foundation for the diver's recognition and detecting technology. This paper also studies the feasible method to detect diver, which is valuable for designing the diver detective sonar.The paper analyses the diver's acoustic characteristics from radiating and scattering, and measures the target strengths of lung cavities and simulated air tanks with the comparative method. This is a confirmation that inhaling is a primary source of diver acoustic emission. When the diver inhales, the sound is composed mainly of high frequencies; when the divers exhales, the sound is mainly at low frequency. The energy of inhaling concentrates and repeats approximately every 3.3 seconds. This is another confirmation that the target strengths of the diver are attributed to the scattering from lung cavities. The paper introduces power spectrum density, short-time Fourier transform and passive acoustic detection algorithm for modulated sounds through aboved conclusion. The paper studies the method of the orientation based on vector-sensor: histogram and weighted histogram, and the trial results shows that the two methods are effective and can be realized.This paper designs software used for generating signal and acquiring and saving signal in the multi-channels. Though the measurements in the tank and the river, it finds out that the acoustic characteristic of the diver. It proves the validity of the recognised arithmetic, and provides theoretical foundation for the detected sonar of the diver.