Fig. 3

Sample result of the phase difference estimation on human-subject AB data. A 60-s sample result of phase difference estimations on human-subject AB data measured by the RIP_TWM (a) and RIP_AWM (b) sensors. The estimation was done by using the loop analysis (c), IPD method (d), and APEP (e). The absent of data for loop analysis in 0–5 and 58–60 s was caused by the incompleteness of cycles. The loop analysis in fact only generates one output value per cycle of breathing at the end of each cycle. The straight lines drawn in the panel c throughout the beginning to the end of each cycle are manually produced after the analysis