Fig. 4From: Detection of sleep disordered breathing severity using acoustic biomarker and machine learning techniquesProcess of qTM extraction. First, absoluted magnitude values are quantized into three levels (silence, low-level signal, high-level signal) for simplification. Among silence periods, apnea candidate periods were determined under standards of AASM and finally signals were quantized into four levels. Temporal transitions of quantized magnitudes were derived and transition probabilities were calculated over whole sleepBack to article page