{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,3]],"date-time":"2026-07-03T10:46:40Z","timestamp":1783075600880,"version":"3.54.6"},"reference-count":46,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2024,10,5]],"date-time":"2024-10-05T00:00:00Z","timestamp":1728086400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"111 Projects","award":["B20039"],"award-info":[{"award-number":["B20039"]}]},{"name":"Tianjin University","award":["B20039"],"award-info":[{"award-number":["B20039"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The detection of bolt looseness is crucial to ensure the integrity and safety of bolted connection structures. Percussion-based bolt looseness detection provides a simple and cost-effective approach. However, this method has some inherent shortcomings that limit its application. For example, it highly depends on the inspector\u2019s hearing and experience and is more easily affected by ambient noise. In this article, a whole set of signal processing procedures are proposed and a new kind of damage index vector is constructed to strengthen the reliability and robustness of this method. Firstly, a series of audio signal preprocessing algorithms including denoising, segmenting, and smooth filtering are performed in the raw audio signal. Then, the cumulative energy entropy (CEE) and mel frequency cepstrum coefficients (MFCCs) are utilized to extract damage index vectors, which are used as input vectors for generative and discriminative classifier models (Gaussian discriminant analysis and support vector machine), respectively. Finally, multiple repeated experiments are conducted to verify the effectiveness of the proposed method and its ability to detect the bolt looseness in terms of audio signal. The testing accuracy of the trained model approaches 90% and 96.7% under different combinations of torque levels, respectively.<\/jats:p>","DOI":"10.3390\/s24196447","type":"journal-article","created":{"date-parts":[[2024,10,7]],"date-time":"2024-10-07T07:30:18Z","timestamp":1728286218000},"page":"6447","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Sound Sensing: Generative and Discriminant Model-Based Approaches to Bolt Loosening Detection"],"prefix":"10.3390","volume":"24","author":[{"given":"Liehai","family":"Cheng","sequence":"first","affiliation":[{"name":"Shandong Electric Power Engineering Consulting Institute Corp., Ltd., Jinan 250013, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-3020-1145","authenticated-orcid":false,"given":"Zhenli","family":"Zhang","sequence":"additional","affiliation":[{"name":"Shandong Electric Power Engineering Consulting Institute Corp., Ltd., Jinan 250013, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0192-3793","authenticated-orcid":false,"given":"Giuseppe","family":"Lacidogna","sequence":"additional","affiliation":[{"name":"Department of Structural, Geotechnical and Building Engineering, Politecnico di Torino, 10129 Torino, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiao","family":"Wang","sequence":"additional","affiliation":[{"name":"School of Civil Engineering, Tianjin University, Tianjin 300350, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-9936-3833","authenticated-orcid":false,"given":"Mutian","family":"Jia","sequence":"additional","affiliation":[{"name":"School of Civil Engineering, Tianjin University, Tianjin 300350, China"},{"name":"Institute of Ocean Energy and Intelligent Construction, Tianjin University of Technology, Tianjin 300384, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhitao","family":"Liu","sequence":"additional","affiliation":[{"name":"School of Civil Engineering, Tianjin University, Tianjin 300350, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,10,5]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"156","DOI":"10.1016\/j.jsv.2016.07.001","article-title":"Quantitative evaluation of residual torque of a loose bolt based on wave energy dissipation and vibroacoustic modulation: A comparative study","volume":"383","author":"Zhang","year":"2016","journal-title":"J. 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