Effects of natural sound exposure on health recovery: A systematic review and meta-analysis.

Listening to natural sounds, both live and recorded, in either a natural or built environment is considered natural sound exposure (NSE). Sound is closely related to daily life, and research on the restorative effects of natural sounds is expanding. However, there is a lack of quantitative and comprehensive analysis on the impact of NSE on health recovery. This study systematically reviewed and conducted a meta-analysis on the impact of NSE on health recovery. Fifteen studies (1285 participants) were selected for the meta-analysis out of the 1157 literatures about the recovery of the NSE, searched from the Web of Science and Science Direct. The results indicate that NSE has certain positive effects: (a) In terms of emotional changes, NSE significantly reduces anxiety as measured by both the Visual Analog Scale (VAS) -2.31 (95 % CI -2.83, -1.79) and the State Anxiety Inventory (SAI) -12.22 (95 % CI -22.46, -1.98). (b) In terms of physiological reaction, NSE resulted in reduced heart rate (HR) -5.46 (95 % CI -9.62, -1.31), systolic blood pressure (SBP) -11.74 (95 % CI -15.51, -7.97), diastolic blood pressure (DBP) -13.98 (95 % CI -24.96, -2.99) and respiratory rate (RR) -1.58 (95 % CI -3.06, -0.10). (c) While the potential for restoration of cognitive performance by NSE was found, no consistent conclusions have been reached yet. However, there was significant heterogeneity between studies, primarily attributed to variations in study populations and methodologies. Because of the limited literature, we did not conduct subgroup analysis and meta-regression analysis. It is recommended that future studies address this heterogeneity by including more and higher-quality literature and employing rigorous methodologies to establish a robust foundation for evidence-based medicine. This will be of great significance for the application natural sounds in landscape planning and medical rehabilitation environments, and has the potential to promote improvements in public health.