Interpretable Low-Pass Acoustic Phenotype in COPD From Chest-Wall Breath Sounds: Spectral Anchors and a Target-Aligned MFCC Axis (ModeT)
İhsan Topaloğlu1, Çağrı Atasoy1, Aylin Bayram1, Nil kuranoğlu1, Gülfem Özduygu2, Mutlu Onur Güçsav3, Abdullah Tanrıkulu4, Yekta Bektaş5, Arif Metehan Yıldız61Department of Pulmonology, Kafkas University Faculty of Medicine, Kars, Türkiye, 2Department of Pulmonology, University of Health Sciences, Yedikule Chest Diseases and Thoracic Surgery Training and Research Hospital, Istanbul, Türkiye, 3Department of Pulmonology, İzmir Bakırçay University, Çiğli Regional Training and Research Hospital, İzmir, Türkiye, 4Department of Internal Medicine, Siirt Training and Research Hospital, Siirt, Türkiye, 5Department of Anesthesiology and Reanimation, Kafkas University Faculty of Medicine, Kars, Türkiye, 6Department of Computer Engineering, Faculty of Engineering, Ardahan University, Ardahan, Türkiye
Objectives: High-frequency breath-sound components are attenuated at the chest wall, producing a low-pass effect. We evaluated this pattern across Healthy controls, Stable chronic obstructive pulmonary disease (COPD), and COPD Exacerbation, and assessed whether a mel-frequency cepstral coefficient (MFCC) axis reflected these states. Methods: We retrospectively analyzed 1,440 posterior recordings from 240 adults (80/group; six 15-s recordings per participant). Spectral bandwidth and 85% spectral roll-off were derived using a short-time Fourier transform pipeline. MFCC1–MFCC13 were summarized by principal component analysis (PCA). ModeT was defined as the PCA component most negatively aligned with both spectral anchors; this rule selected PC6. Results: Bandwidth differed across groups (210.19, 204.96, 206.89; p=0.002), as did roll-off (303.35, 299.47, 297.89; p=0.013) and ModeT (?0.08, ?0.05, 0.14; p=0.001). Ordered trends were significant for all three measures. ModeT explained 3.9% of MFCC variance, correlated with both anchors, and remained higher in Exacerbation than Healthy in clustered record-level models (estimate 0.22, 95% CI 0.09–0.34; p<0.001). Conclusion: COPD chest-wall recordings show a low-pass spectral shift. Spectral anchors and ModeT define an interpretable acoustic phenotype requiring prospective validation. Keywords: Chronic obstructive pulmonary disease (COPD); respiratory sound analysis; electronic stethoscope; low-pass acoustic phenotype; mel-frequency cepstral coefficients (MFCC)
Cite This Article
Topaloğlu İ, Atasoy Ç, Bayram A, kuranoğlu N, Özduygu G, Onur Güçsav M, Tanrıkulu A, Bektaş Y, Yıldız A. Interpretable Low-Pass Acoustic Phenotype in COPD From Chest-Wall Breath Sounds: Spectral Anchors and a Target-Aligned MFCC Axis (ModeT). EJMI. 2026; 10(3): 269-278
Corresponding Author: İhsan Topaloğlu