Multi-Stage Feature Extraction and Classification for Ship-Radiated Noise

Due to the complexity and unique features of the hydroacoustic channel, ship-radiated noise (SRN) detected using a passive sonar tends mostly to distort. SRN feature extraction has been proposed to improve the detected passive sonar signal. Unfortunately, the current methods used in SRN feature extraction have many shortcomings. Considering this, in this paper we propose a new multi-stage feature extraction approach to enhance the current SRN feature extractions based on enhanced variational mode decomposition (EVMD), weighted permutation entropy (WPE), local tangent space alignment (LTSA), and particle swarm optimization-based support vector machine (PSO-SVM). In the proposed method, first, we enhance the decomposition operation of the conventional VMD by decomposing the SRN signal into a finite group of intrinsic mode functions (IMFs) and then calculate the WPE of each IMF. Then, the high-dimensional features obtained are reduced to two-dimensional ones by using the LTSA method. Finally, the feature vectors are fed into the PSO-SVM multi-class classifier to realize the classification of different types of SRN sample. The simulation and experimental results demonstrate that the recognition rate of the proposed method overcomes the conventional SRN feature extraction methods, and it has a recognition rate of up to 96.6667%.

Comparison of Passive Sonar Narrowband Detection and Wideband Detection Performance

Conventional passive sonar uses wideband beam energy for target detection. In the case of low signal-to-noise ratio and strong target interference, the performance of wideband energy detection is rapidly degraded. In view of the relatively stable line spectrum of the radiated noise of underwater targets, the performance of narrowband detection and wideband detection is considered. In stable line spectrum underwater target detection, narrowband detection has performance advantages over wideband detection. However, its actual performance has disadvantages such as sensitivity to noise frequency bands. In this paper, based on the sonar equation, the theoretical methods of wideband detection and narrowband detection are analyzed and the main factors affecting detection performance are given. Simulation and sea trial data processing results verify the effectiveness of the method.