Fig. 4: Cumulative distribution functions (CDFs) of absolute error in R–R intervals in different sessions with healthy participants.

A CDFs at different distances (red line, black dashed line, and blue dotted line represent 40, 50, and 60 cm, respectively) from the speaker, B CDFs with the speaker pointing left at a 20° angle (red line) from the chest, compared to right in front of the chest (black dashed line), C CDFs with the speaker pointing 10 cm above chest (red line), D CDFs with music playing in the background (red line), E CDFs after exercising in the last session (red line), and F CDFs across genders (red line and dashed blue line represent female and male, respectively).