Evaluation of Auditory Fatigue in Combined Noise, Heat and Workload Exposure

Abstract

This study was performed in a climatic chamber to evaluate the combined effects of noise intensity, heat stress, workload, and exposure duration on both noise-induced temporary threshold shift (TTS) and the recovery time by adopting Taguch's method. Fourteen subjects without previous significant noise exposure and smoking history were recruited to participate in this study. All hearing threshold levels at eight different frequencies (250 to 8,000 Hz) of better ear were measured in an audiometric booth by using the ascending method in 2 dB steps before each exposure condition. The test was also carried out after exposure to evaluate TTS at various times. The TTS recovery time was assessed using an audiometric test on all subjects at post-exposure times of 2, 20, 40, 60, 80 and 120 min, respectively. It was found that TTS depended mainly on the exposed noise dose and was enhanced by workload and heat stress. The TTS recovery time is dependent upon the magnitude of the initial hearing loss. In conclusion, TTS driven by noise exposure is enhanced by heat and workload. Further studies are required to evaluate the effects of workload with extreme temperature in a workplace environment.

‘Ecstasy’ enhances noise-induced hearing loss

“…The toxicity of MDMA is often dependent on its hyperthermic effects (Johnson & Yamamoto, 2010) and hyperthermia can enhance NIHL (Chen et al, 2007). However, in the present study, there was no correlation between these parameters in the Noise+MDMA group, the Noise-only group, or these two groups combined.…”

“…When any 2-way ANOVA indicated a significant treatment group main effect or interaction, simple effects tests (1-way ANOVAs) and Student-Newman-Keuls or paired t-tests were used to make post hoc pairwise comparisons between individual treatment groups. Whereas hyperthermia can enhance NIHL (Chen et al, 2007) and MDMA can induce hyperthermia (Johnson & Yamamoto, 2010), the correlation (Pearson r) was calculated between the body temperatures recorded just prior to the noise trauma and the subsequent NIHL using data from the two groups that were exposed to the noise trauma. This comparison determined if there was a relationship between the amount of NIHL and an animal’s body temperature at the time of noise trauma.…”

Activity of coenzyme Q10(Q-Ter multicomposite) on recovery time in noise-induced hearing loss

“…In fact, recovery time can be considered an indicator of the psycho-physical cost of noise exposure because, unlike the TTS, it is strongly infl uenced by the characteristics of the fatiguing stimulation (frequency, intensity, and duration) as well as by interindividual differences. [3,6,33,34] The threshold shift induced by the stimulus used in this study was signifi cant at high frequencies (4000-8000 Hz) which, due to the tonotopic organization of the cochlea, are received by receptors in the basal turn of the cochlea.…”

“…[3][4][5] The recovery time is related to the amount of initial hearing loss (being longer the greater the initial hearing loss) and mostly occurs during the fi rst 15 min following exposure. [3,6] Traditionally, the prevention of noise-induced hearing loss (NIHL) has been addressed by providing wearable hearing protection (earplugs, earphones) and reducing noise emissions. [7] Clinical and preclinical trials for drugs that could reduce TTS and PTS retrace the understanding of the physiopathology of NIHL.…”

PON2 and ATP2B2 gene polymorphisms with noise-induced hearing loss

“…Exposure to noise is the best known environmental factor that causes hearing loss. Other environmental factors include heat, organic solvents, infections and ototoxic agents which have also been demonstrated to contribute to NIHL (3)(4)(5). In addition, individual factors such as smoking, high blood pressure, and medical factors may influence the susceptibility to noise (6)(7)(8)(9).…”