{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,6]],"date-time":"2026-02-06T22:50:19Z","timestamp":1770418219923,"version":"3.49.0"},"reference-count":33,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2020,4,20]],"date-time":"2020-04-20T00:00:00Z","timestamp":1587340800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"The National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["61671394"],"award-info":[{"award-number":["61671394"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>Due to the complexity and variability of underwater acoustic channels, ship-radiated noise (SRN) detected using the passive sonar is prone to be distorted. The entropy-based feature extraction method can improve this situation, to some extent. However, it is impractical to directly extract the entropy feature for the detected SRN signals. In addition, the existing conventional methods have a lack of suitable de-noising processing under the presence of marine environmental noise. To this end, this paper proposes a novel feature extraction method based on enhanced variational mode decomposition (EVMD), normalized correlation coefficient (norCC), permutation entropy (PE), and the particle swarm optimization-based support vector machine (PSO-SVM). Firstly, EVMD is utilized to obtain a group of intrinsic mode functions (IMFs) from the SRN signals. The noise-dominant IMFs are then eliminated by a de-noising processing prior to PE calculation. Next, the correlation coefficient between each signal-dominant IMF and the raw signal and PE of each signal-dominant IMF are calculated, respectively. After this, the norCC is used to weigh the corresponding PE and the sum of these weighted PE is considered as the final feature parameter. Finally, the feature vectors are fed into the PSO-SVM multi-class classifier to classify the SRN samples. The experimental results demonstrate that the recognition rate of the proposed methodology is up to 100%, which is much higher than the currently existing methods. Hence, the method proposed in this paper is more suitable for the feature extraction of SRN signals.<\/jats:p>","DOI":"10.3390\/e22040468","type":"journal-article","created":{"date-parts":[[2020,4,21]],"date-time":"2020-04-21T03:23:06Z","timestamp":1587439386000},"page":"468","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":27,"title":["Feature Extraction of Ship-Radiated Noise Based on Enhanced Variational Mode Decomposition, Normalized Correlation Coefficient and Permutation Entropy"],"prefix":"10.3390","volume":"22","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4279-0501","authenticated-orcid":false,"given":"Dongri","family":"Xie","sequence":"first","affiliation":[{"name":"School of Electronic Science and Engineering, Xiamen University, Xiamen 361005, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7317-8908","authenticated-orcid":false,"given":"Hamada","family":"Esmaiel","sequence":"additional","affiliation":[{"name":"Department of Information and Communication, School of Informatics, Xiamen University, Xiamen 361005, China"},{"name":"Electrical Engineering Department, Faculty of Engineering, Aswan University, Aswan 81542, Egypt"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8249-1197","authenticated-orcid":false,"given":"Haixin","family":"Sun","sequence":"additional","affiliation":[{"name":"School of Informatics, Xiamen University, Xiamen 316005, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jie","family":"Qi","sequence":"additional","affiliation":[{"name":"School of Electronic Science and Engineering, Xiamen University, Xiamen 361005, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Zeyad A. H.","family":"Qasem","sequence":"additional","affiliation":[{"name":"School of Informatics, Xiamen University, Xiamen 316005, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,4,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"20170143","DOI":"10.1098\/rspb.2017.0143","article-title":"Motorboat noise impacts parental behaviour and offspring survival in a reef fish","volume":"Volume 284","author":"Nedelec","year":"2017","journal-title":"Proceedings of the Royal Society B: Biological Sciences"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Rossi, E., Licitra, G., Iacoponi, A., and Taburni, D. (2016). Assessing the underwater ship noise levels in the North Tyrrhenian Sea. 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