Stress recovery at home: Effects of the indoor visual and auditory stimuli in buildings

In order to explore the potential contribution of the visual and auditory environment on the mental stress recovery of people in indoor environment, the visual, auditory, and visual-auditory stimuli were selected to design 3 kinds of restorative environments, under which the subjects experienced the baseline stage, the stress-induction stage, and the recovery stage, in sequence. The stress was induced with the continuous high frequency noise at 70–80 dB. The Electrocardiogram (ECG) data of the subjects were recorded during the whole experiment, and the heart rate variability (HRV) analysis was conducted, producing the mean heart rate (HR), the root mean square successive difference (RMSSD), as well as the ratio of low to high frequency power (LF/HF). The stress level was evaluated with these indexes during the whole experiment. Results showed that mean HR and LF/HF were higher than that of the baseline after the stress-induction, while the mean RMSSD was significantly lower than the baseline level, which implied the stress rise was resulted from the stress-induction stage. In addition, it was found that the mean HR and LF/HF reduced after the participants experienced the visual, the auditory and the visual-auditory restorative environments, but the mean RMSSD increased, which suggested the attenuated stress level. Furthermore, it was observed that the RMSSD was the most sensitive to the stress. Based on that, the time for the stress-recovery was estimated with the mean RMSSD. Results showed that the visual and visual-auditory stimuli produced better acute recovery effect than that of the auditory, but in the long run the auditory stimulus could bring the most stress reduction, followed by the visual stimulus. This study produced a potential solution for the stress recovery at home, which could be important for the improvement of the mental health, cognitive performance and the productivity of the occupants.