Effects of thermal and acoustic environments on workers' psychological and physiological stress in deep underground spaces

With the development of urbanization, the development of deep underground spaces has become increasingly important. The purpose of this research is to study how the combined effects of thermal and acoustic environments affect psychological and physiological stress of workers in deep undergrounds spaces. A randomized crossover chamber study with 16 subjects was carried out in this study. Participants were exposed to two different temperatures (30 and 34 °C), two different relative humidity levels (65 and 85%), and three different noise levels (55, 70 and 85 dBA). The experimental protocol included subjective thermal sensation, emotion, heart rate variability, skin temperature and cognitive performance tests. Results showed that temperature and relative humidity affected the change of emotion via their influence on thermal responses. In deep underground spaces, participants were always in a state of tension. The effect of temperature on low to high frequency ratio (LF/HF) was more pronounced at high noise levels. Low relative humidity could compensate for the discomfort caused by high temperatures. In general, temperature had the greatest influence, and the combined effect was significantly greater than the individual effect on workers' psychological and physiological stresses.