Chronic Noise Affects Middle Ear Resonance and Absorbance in Industrial Workers

BACKGROUND: The effect of chronic noise on the middle ear is not fully known. This study aimed to evaluate the middle ear functions of metal workers exposed to chronic noise using wideband tympanometry. METHODS: In this study, 62 male workers exposed to chronic noise and 30 healthy men were included. Workers exposed to chronic noise were divided into 2 groups according to their pure tone averages. Totally 30 workers (60 ears) with pure tone average less than 20 dB were included in group I, and 32 workers (64 ears) with pure tone average more than 20 dB were included in group II. All individuals were subjected to wideband tympanometry. Tympanometric peak pressure, equivalent ear canal volume, static acoustic admittance, resonance frequency, and absorbance ratios at peak pressure and ambient pressure values were analyzed. RESULTS: There was no difference between the groups in terms of traditional tympanometric parameters such as tympanometric peak pressure, equivalent ear canal volume, and static acoustic admittance (P >.05). Resonance frequency of workers exposed to chronic noise (group I and group II) was lower than the control group (P <.05). The absorbance ratios of workers exposed to chronic noise at approximately 4 kHz were lower in both peak pressures and ambient pressures (P <.05). CONCLUSION: Chronic noise does not only damage the inner ear but also causes changes in the middle ear structures. Wideband tympanometry can be used to detect minor auditory damage due to noise that cannot be detected by audiogram early. In this way, necessary measures can be taken in the early period before noise-induced hearing loss occurs.