Research on the Ambient Noise Observation Technology Based on the Underwater Glider

The underwater glider is a new type of unpowered, unmanned, moving observational platform with advantages of low-noise level, long operation time, far sustainable range, and high cost-effectiveness. In the paper, based on the underwater glider platform integrated with single vector acoustic sensor, an underwater acoustic glider platform is developed with the ability to detect target direction and observe the ambient noise. The acoustic measurement system and the self-noise of the glider platform under each working condition are tested to analyze the self-noise levels of the acoustic system and the primary noise sources of the platform, and conduct the vibration and noise reduction processing of the platform and optimize the working mode of the acoustic system. The test result shows that the underwater acoustic glider with the optimization has the ability to observe the ambient noise only on the pressure hydrophone channel. With the data sampled from one of the underwater gliders of the sea trial organized in a certain area of the South China Sea in August 2019, authors analyze the variation of spectrum levels of the ambient noise with the depth and the time at the center of seven frequency points (63 Hz, 100 Hz, 200 Hz, 400 Hz, 800 Hz, 1.6 kHz and 3.15 kHz) and discuss the influence of the sailing vessel close to the glider on it. The experimental result shows that the underwater acoustic glider, as an unscrewed moving platform, can be well used to monitor the ambient noise properties over a long term.