Since occupational hearing loss is frequently non-curable, results of accurate prediction can be used by occupational health experts to modify and improve noise exposure conditions.

Background: This study aimed to investigate the effect size (ES) of air temperature on the executive functions of human brain and body physiological responses.Methods: In this empirical study, the participants included 35 male students who were exposed to 4 air temperature conditions of 18°C, 22°C, 26°C and 30°C in 4 separate sessions in an air conditioning chamber. The participants were simultaneously asked to take part in the N-back test. The accuracy, electrocardiogram (ECG) signals and the respiration rate were recorded to determine the effect of air temperature. Results: Compared to moderate air temperatures (22°C), high (30°C) and low (18°C) air temperatures had a much more profound effect on changes in heart beat rate, the accuracy of brain executive functions and the response time to stimuli. There were statistically significant differences in the accuracy by different workload levels and various air temperature conditions(P<0.05). Although the heart beat rate index, the ratio between low frequency and high frequency (LF/HF), and the respiratory rate were more profoundly affected by the higher and lower air temperatures than moderate air temperatures (P<0.05), this effect was not statistically significant, which may be due to significant reduction in the standard deviation of normal-to normal intervals (SNND) and the root of mean squared difference between adjacent normal heart beat (N-N) intervals (RMSSD) (P>0.05). Conclusion: The results confirmed that the unfavorable air temperatures may considerably affect the physiological responses and the cognitive functions among indoor employees.Therefore, providing them with thermal comfort may improve their performance within indoor environments.

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Tasks requiring intensive concentration are more vulnerable to noise than routine tasks. Due to the high mental workload of bank employees, this study aimed to evaluate acoustic comfort in open-space banks based on speech intelligibility and noise annoyance metrics. Acoustic metrics including preferred noise criterion (PNC), speech transmission index (STI), and signal to noise ratio (SNR) were measured in seventeen banks (located in Hamadan, a western province of Iran). For subjective noise annoyance assessments, 100-point noise annoyance scales were completed by bank employees during activities. Based on STI (0.56±0.09) and SNR (20.5±8.2 dB) values, it was found that speech intelligibilities in the workstations of banks were higher than the satisfactory level. However, PNC values in bank spaces were 48.2±5.5 dB, which is higher than the recommended limit value for public spaces. In this regard, 95% of the employees are annoyed by background noise levels. The results show irrelevant speech is the main source of subjective noise annoyance among employees. Loss of concentration is the main consequence of background noise levels for employees. The results confirmed that acoustic properties of bank spaces provide enough speech intelligibility, while staff’s noise annoyance is not acceptable. It can be concluded that due to proximity of workstations in open-space banks, access to very short distraction distance is necessary. Therefore, increasing speech privacy can be prioritised to speech intelligibility. It is recommended that current desk screens are redesigned in order to reduce irrelevant speech between nearby workstations. Staff’s training about acoustic comfort can also manage irrelevant speech characteristics during work time.

The purpose of this study was to investigate the physiological and mental health effects caused by exposure to low-frequency noise in typical control rooms and office-like areas. The participants were 35 male students who were exposed to noise at levels of 55, 65, 70, and 75 dBA. The N-back test was used at three cognitive performance loads (low workload (n = 1), medium workload (n = 2), and high workload (n = 3) to evaluate working memory simultaneously in an air conditioning chamber in four sessions with a constant level. The electroencephalography, electrocardiogram, and electrooculography were measured using Nexus 4 by Bio traces software (Mind Media Co.). For evaluation of mental fatigue, fatigue visual analog scale, and psychophysiological indices were also used. The results showed that the losses of physiological and mental health were rapidly increased with exposure to noise levels of 65-75 dBA. The results showed that mental fatigue significantly affected heart rate, low-to high-frequency ratios, and electroencephalogram indices such as theta, alpha, as well as eye activities and working memory. The findings confirmed that the mental fatigue caused by low-frequency noise significantly impacted the employees' psycho-physiological and working memory responses. Implementation of the effective interventions to overcome employees' mental fatigue in typical control rooms and office-like areas can improve the health and acoustic comfort and, consequently, the cognitive performance.