Testing the stationarity and normality of paediatric aspiration signals

Ninety-four aspiration signals were collected with a single-axis accelerometer placed infero-anterior to the thyroid notch from 23 children with Dysphagia. It was found that only 62% of aspiration signals can be considered stationary over short finite time windows. Further, 96% of aspiration signals violated normality to varying degrees. Nonstationarity was attributed to time-varying variance structure while departure from normality was linked to leptokurtic (more peaked than a normal distribution) amplitude distributions. Conventional assumptions of stationarity and normality do not simultaneously hold true for aspiration signals. Implications for automatic detection are mentioned.