Research On Tow Noise Identification For Optical Fiber Hydrophone Linear Array

The towed linear array sonar is far away from the carrier platform,and is less affected by the ship’s vibration and radiation noise.The array length is not limited by the space size of the carrier platform.The space gain is high.The working depth is flexible and variable.Therefore,it can use various underwater acoustic propagation effects to achieve optimal detection of targets.Because the towed linear array sonar is particularly suitable for low-frequency and long-distance underwater acoustic detection,it has become an effective solution for the current low-noise submarine long-distance detection.During the towing reconnaissance process of the towed line array sonar,various types of noise are superimposed together to form the tow noise of the array,which seriously affects the detection performance of the towed linear array,and has become a key issue restricting the development and application of towed linear array sonar.Different types of tow noise have different generating mechanisms,which have different degrees of impact on the detection performance of the towed linear array.Therefore,identifying and classifying linear array tow noise are prerequisites for proposing targeted noise suppression methods,and are key steps to reduce the noise level of towed linear array sonar effectively.Aiming at the problem that complex tow noise was produced by the linear array sonar during the working process and the noise will affect the detection performance.This paper carries out the research on tow noise identification for optical fiber hydrophone linear array.Classify and summarize the tow noise of linear array.Review the generation mechanism,acoustic characteristics and several commonly used noise identification methods.Give the basic steps of processing noise data with noise spectrum analysis method,and analyze the typical tow data of optical fiber linear array.Propose a method to identify tow noise based on the slope of the noise power spectrum.Analyze the acoustic characteristics of the tow noise power spectrum at different tow speeds.Introduce the basic principle of wavenumber-frequency spectrum analysis for tow noise identification.Simulate and analyze the tow noise identification of single-frequency targets and broadband targets.Verify the validity of the method with the lake trial data and sea trial data.Analyze the difference between the spatial coherence of the flow noise and the environmental noise.Propose the coherence coefficient extraction method from the measured data.Through the analysis and processing of the lake trial data,realize the purpose of separating the flow noise from the original noise data.There are two main innovations in this paper:(1)Propose a method to analyze noise types based on the slope of the noise power spectrum.Through theoretical and experimental analysis,the noise spectrum slope characteristics of each noise source at different tow speeds are obtained.(2)Discuss a method to separate flow noise based on data-extracted coherence.Through experimental analysis,the effectiveness of this method for the identification of coherent noise and incoherent noise is verified.