The acoustics of coughing

Coughing is a reflex‐generated perturbation of the respiratory function and an important clinical symptom in many respiratory diseases. The information contained in the cough‐sound is limited due to the lack of an understanding of the origin of the cough sound. This thesis focuses on (1) automated interpretation, (2) quantification, and (3) sound‐production. “ In vivo ” coughing was registered from individual animal (domestic pig Sus Scrofa ) and human subjects in normal and pathological respiratory health conditions. The cough‐sound is mathematically presented in the frequency domain. Clustering of the mean spectral features results in automated subject‐independent cough‐sound‐recognition. In addition normal and pathological cough‐sounds are distinct for both species. Therefore the simple and noninvasive nature of acquiring information using free field cough‐sound‐registration makes sound analysis attractive for on‐line follow‐up and clinical diagnosis. The vibratory activity of the vocal folds is known to be an important issue in sound production. A three‐phase pattern is shown to be a generic cough‐feature. A global fundamental frequency was determined. Modeling the acoustic cough waveform aims to parametrize the cough‐sound‐signal for analysis and physical interpretation. Cough formant frequencies are estimated from the model parameters. A first physical interpretation in terms of a concatenate tube model of the vocal tract is presented. All investigated issues, either parametric or nonparametric, show evidence that the cough‐sound character is related to the state of both the supra‐ and subglottal respiratory system. This finding physically and objectively motivates the statement the “cough‐sound is a lung‐sound.”