{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,20]],"date-time":"2026-02-20T09:19:46Z","timestamp":1771579186615,"version":"3.50.1"},"reference-count":57,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2026,2,20]],"date-time":"2026-02-20T00:00:00Z","timestamp":1771545600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100000038","name":"Natural Science and Engineering Research Council of Canada","doi-asserted-by":"publisher","award":["RGPIN-2023-04308"],"award-info":[{"award-number":["RGPIN-2023-04308"]}],"id":[{"id":"10.13039\/501100000038","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Obstructive sleep apnea (OSA), defined by repetitive airway obstruction during sleep, is significantly underdiagnosed, mainly due to the resource-intensive and time-consuming nature of sleep assessment technologies. Machine learning analysis of the tracheal breathing sounds (TBS) whilst awake offers an alternative approach for OSA quick screening. This study aimed to address the challenge of wakefulness OSA detection using TBS recorded with an inexpensive microphone in a noisy environment. Data of 247 individuals with various degrees of OSA severity were analyzed. Recorded data were segmented into inspiration and expiration phases, followed by acoustic features extraction, feature reduction, and classification. A two-level ensemble architecture was implemented. Nine sub-classifiers were stratified by anthropometric profiles. Each sub-classifier was constructed as an ensemble of bagged decision trees, with a final prediction via probability-based voting. The proposed algorithm achieved an accuracy of 77.1%, sensitivity of 84.3%, and specificity of 59.9%. Although these results have lower performance than those obtained previously using a high-quality microphone in a quiet room, they demonstrate that acoustic OSA detection whilst awake remains feasible, even in very noisy environments. Nevertheless, microphone quality emerged as a key determinant of classification performance.<\/jats:p>","DOI":"10.3390\/s26041349","type":"journal-article","created":{"date-parts":[[2026,2,20]],"date-time":"2026-02-20T08:50:03Z","timestamp":1771577403000},"page":"1349","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["A Two-Level Ensemble Machine Learning Framework for OSA Classification Whilst Awake from Noisy Tracheal Breathing Sounds"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0009-0000-7406-4152","authenticated-orcid":false,"given":"Vahid","family":"Bastani Najafabadi","sequence":"first","affiliation":[{"name":"Department of Electrical and Computer Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1593-6285","authenticated-orcid":false,"given":"Walid","family":"Ashraf","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ahmed","family":"Elwali","sequence":"additional","affiliation":[{"name":"Department of Biomedical Engineering, Marian University, Indianapolis, IN 46222, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9202-949X","authenticated-orcid":false,"given":"Zahra","family":"Moussavi","sequence":"additional","affiliation":[{"name":"Department of Electrical and Computer Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada"},{"name":"Department of Biomedical Engineering, University of Manitoba, Winnipeg, MB R3T 2N2, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,2,20]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1442","DOI":"10.1056\/NEJMcp1816152","article-title":"Obstructive Sleep Apnea in Adults","volume":"380","author":"Veasey","year":"2019","journal-title":"N. 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