Effects of natural sound on human stress recovery based on EEG techniques

Natural sounds are an essential part of a restorative environment. Although numerous studies have established the positive impact of natural sounds on human health and well-being, few have examined the differences between natural sounds on human stress recovery. This study examined the impact of natural sounds on stress recovery by comparing a silent environment (control group) with three experimental groups exposed to flowing water sound, birdsong, and wind sounds. The investigation entailed the assessment of subjective assessments and EEG signals from 30 subjects (12 males and 18 females). The subjective evaluations indicated that the PRS scores for the sounds of flowing water and birdsong were superior to those of the silent environment. The EEG results revealed that EEG-α activity was more pronounced in response to natural sounds than the silent environment, with birdsong evoking the most significant EEG-α activity. Wind sounds increased the mental stress of the subjects. Conversely, birdsong and flowing water sound were beneficial for alleviating mental stress. Additionally, the analysis of event-related potentials (ERP) demonstrated that natural sounds elicited higher P300 amplitudes in central and parietal lobe sensors and had little effect on the frontal region. The study also demonstrated the correlation between EEG and subjective stress evaluations, providing insights into stress reduction theories and offering practical suggestions for optimizing the acoustic environment in urban settings.