Alleviating Surgeons' Stress through Listening to Natural Sounds in a Half-Encapsulated Rest Space after an Operation: A Pilot, Longitudinal Field Study.

BACKGROUND: Natural sounds are reportedly restorative, but most research has used one-off experiments conducted in artificial conditions. Research based on field experiments is still in its infancy. This study aimed to generate hypotheses on the restorative effects of listening to natural sounds on surgeons, representing professionals working in stressful conditions. METHODS: Each of four surgeons (two experts and two residents) participated six times in an experiment where they took a 10-min break listening to natural sounds (four times) or without natural sounds (twice) after a surgical operation. We measured their skin conductance level, an indicator of sympathetic arousal, continuously during the break (measurement occasions N = 2520) and assessed their mood using two questionnaires before and after the break (N = 69 and N = 42). We also interviewed them after the break. RESULTS: Based on statistical Linear Mixed-Effects modeling, we developed two hypotheses for further, more detailed studies: (H1) Listening to natural sounds after an operation improves surgeons' mood. (H2) Inexperienced surgeons' tension persists so long that the effect of natural sounds on their sympathetic arousal is negligible. CONCLUSIONS: This risk-free, easy-to-use means of stress alleviation through natural sounds could benefit highly-stressed people working indoors.

Effect of Faint Road Traffic Noise Mixed in Birdsong on the Perceived Restorativeness and Listeners' Physiological Response: An Exploratory Study.

Many studies have reported that natural sounds (e.g., birdsong) are more restorative than urban noise. These studies have used physiological and psychological indicators, such as the skin conductance level (SCL) and the Perceived Restorativeness Scale (PRS), to evaluate the restorative effect of natural sounds. However, the effect of faint background noise mixed with birdsong on the restorativeness of birdsong has not been described yet. In the current experiment, we examined whether traffic noise affects the perceived restorativeness and the physiological restorativeness of birdsong in a low-stress condition using the SCL and the PRS. The scores of the PRS showed that birdsong significantly increased the perceived restorativeness of the place regardless of the car noise, but no significant difference was found between these two birdsongs. In contrast, physiologically, the birdsong without car noise decreased the participants' SCL significantly more than the birdsong with car noise did. These results indicate that the SCL would be useful to detect the effect of background noise on natural sound when the noise is too low to affect the perceived restorativeness. This study highlights the importance of measuring the SCL besides assessing perceived restorativeness to describe the characteristics of restorative natural sound in future research.

Approximate theory of reverberation in rectangular rooms with specular and diffuse reflections.

First, an approximate theory of reverberation in rectangular rooms is formulated as a specular reflection field based on the image source method. In the formulation, image sources are divided into axial, tangential, and oblique groups, which chiefly contribute to the corresponding groups of normal modes in wave acoustics. Consequently, the total energy decay consists of seven kinds of exponential decay curves. Second, considering surface scattering on walls with scattering coefficients, an integrated reverberation theory for nondiffuse field is developed, where the total field is divided into specular and diffuse reflection fields. The specular reflection field is simply formulated by substituting specular absorption coefficients, while the diffuse reflection field is assumed to be a perfectly diffuse field, of which energy is supplied from the specular reflection field at each reflection. Finally, a theoretical case study demonstrates how surface scattering affects the energy decay in rectangular rooms with changing the aspect ratio and the absorption distribution.