Impact of thermal-acoustic exposure on human performance of healthy adults: simulation of traffic noise and thermal conditions in the urban environment

Occupants in many urban and occupational environmental settings are simultaneously exposed to environmental traffic noise and heat stress. These combined exposures may have adverse effects on physiological functions and cognitive performance. This study aimed to assess the effects of concurrent exposure to traffic noise and thermal stress under controlled laboratory conditions. In this crossover experimental study, 80 healthy participants (mean age: 25.3 ± 2.8 years) were exposed to four exposure conditions: (1) control (comfort), (2) thermal (WBGT = 30.62 °C), (3) traffic noise (75 dB_A), and (4) combined exposure (WBGT = 30.62 °C and75 dB_A). Physiological parameters including heart rate, blood pressure, tympanic temperature, and mean skin temperature were recorded. Cognitive performance was assessed using the Stroop test (for selective attention) and n-back test (for working memory). Repeated-measures ANOVA was used for statistical analysis. Exposure to combined heat and traffic noise produced the most pronounced physiological and cognitive alterations among all test conditions. Core temperature rose significantly during noise (p = 0.008) and combined exposure (p = 0.007). Diastolic blood pressure increased under thermal (p = 0.001) and combined conditions (p < 0.001). Heart rate also elevated during combined exposure (p = 0.032). CPT reaction time lengthened significantly across conditions (p = 0.001), with the thermal and combined situation more than control (post hoc p < 0.05, p < 0.01). All n-back outcomes showed statistically significant differences across exposure conditions at levels 2 and 3, and for incorrect responses and mean reaction time at level 1 (p < 0.001). Simultaneous exposure to traffic noise and thermal stress amplifies both physiological strain and cognitive impairment compared to single exposures. These findings highlight the importance of integrated exposure assessment and risk mitigation strategies in occupational environments, especially in warm and noisy settings.