Tracheal Sounds Features Changes in Different Sleep Stages Based on Complex Wavelet Analysis.

Breathing sounds analysis during sleep is an informative method to study the upper airway. Different sleep stages may affect the breathing sound features. In this study, the tracheal breathing sounds were recorded from 5 individuals and the complex Gaussian wavelet of the deceleration phase of about 3000 successive breath cycles were calculated. The segmented portions were divided into 30 seconds episodes and the appropriate sleep stage of each segment were labeled. The results showed that the Mahalanobis distance between the real parts of the complex Gaussian wavelet coefficients and the reference distribution of each stage is changing consistently in different sleep stages.