Physiological and Psychological Effects of Forest and Urban Sounds Using High-Resolution Sound Sources.

Jo Jo,Kobayashi Kobayashi,Ikei Ikei,Miyazaki Miyazaki,Song Song,Enomoto Enomoto

doi:10.3390/ijerph16152649

Abstract

Exposure to natural sounds is known to induce feelings of relaxation; however, only few studies have provided scientific evidence on its physiological effects. This study examined prefrontal cortex and autonomic nervous activities in response to forest sound. A total of 29 female university students (mean age 22.3 ± 2.1 years) were exposed to high-resolution sounds of a forest or city for 60 s, using headphones. Oxyhemoglobin (oxy-Hb) concentrations in the prefrontal cortex were determined by near-infrared spectroscopy. Heart rate, the high-frequency component of heart rate variability (which reflects parasympathetic nervous activity), and the ratio of low-frequency to high-frequency (LF/HF) components (which reflects sympathetic nervous activity) were measured. Subjective evaluation was performed using the modified semantic differential method and profiles of mood states. Exposure to the forest sound resulted in the following significant differences compared with exposure to city sound: decreased oxy-Hb concentrations in the right prefrontal cortex; decreased ln(LF/HF); decreased heart rate; improved feelings described as “comfortable,’’ “relaxed,” and “natural”; and improved mood states. The findings of this study demonstrated that forest-derived auditory stimulation induced physiological and psychological relaxation effects.

Highlights

Human physiological functions have adapted to the natural environment over 6–7 million years of human evolution [1,2]
In the right prefrontal cortex (Figure 3a), changes in the oxy-Hb concentration were similar for the forest and city sounds for the (Figure 3a), changes in the oxy-Hb concentration were similar for the forest and city sounds for the first 15 s after exposure
This study examined the physiological effects of exposure to forest sound on brain and autonomic nervous activities measuring concentration theexposure prefrontaltocortex and

Summary

Introduction

Human physiological functions have adapted to the natural environment over 6–7 million years of human evolution [1,2]. Since the industrial revolution, an increasing number of people have moved from natural to artificial urban environments. Human physiology, which has evolved in response to the natural environment, has had little time to adapt to the artificial environments of urban areas. Some researchers have proposed this to be a reason why many people in urban areas experience stress and tension [2,4,5]. The relaxing and restorative effects of the natural environment have gradually gained attention [4,5,6,7], with the development of physiological measurement technology facilitating the accumulation of scientific evidence based on physiological parameters

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