The effect of auditory stimulation on the nonlinear dynamics of heart rate: the impact of emotional valence and arousal

Background Although it is known that sound exposure evokes changes in autonomic activity, the effects of noise and music on the nonlinear behavior of heart rate fluctuations remain poorly understood and controversial. This study aims to assess the influence of sound subjective emotional valence and arousal on the nonlinear characteristics of the autonomic nervous system during passive listening. Methods In this study, forty-two subjects listened to four sounds: (1) white noise, (2) road traffic noise, (3) excitatory music, and (4) a lullaby. The experiment consisted of two consecutive sessions: five minutes of rest, followed by five minutes of listening. RR intervals were recorded during both sessions. The following linear and nonlinear heart rate variability indices were computed: SDNN, RMSSD, F, HF, approximate (ApEn) and sample entropy (SampEn), correlation dimension (D2), Poincare plot indices (SD1, SD2), fractal scaling exponents (alpha1, alpha2), and recurrence plot indices (Lmean, Lmax, DET, LAM, Vmax, TT, ShanEn). Results Excitatory music was associated with significant decrease in SDNN and RMSSD, diminished HF, and a substantial reduction in LF. Excitatory music exposure induced significant increases in DET, SD1 and SD2, but changes in DFA, SampEn, and D2 were nonsignificant. Traffic noise, white noise, and the lullaby did not cause significant changes in the measures of heart rate variability. Conclusion Presentation of music evoking strong negative emotions elicits a prominent decrease in respiratory sinus arrhythmia. Poincare plot and recurrence plot measures possess high sensitivity to high arousal and unpleasant music. Contrary to previous studies, we did not find the effects of relaxing music on heart rate variability.