Abstract
Most of the persons with noise exposure will have clinically normal hearing threshold while experiencing reduced speech comprehension. The motive of this study is to assess the impact of occupational noise on the encoding of speech stimuli in the auditory system in the auto-rickshaw drivers and compare the auditory brainstem responses (ABR) using speech stimuli with that of controls. The study was done in experimental design, where speech evoked ABR was measured in 21 auto-drivers who were continuously exposed to higher levels of occupational noise, and they were compared to the results of 37 individuals who were not exposed to noise. Speech ABR was administered in both the groups and the absolute latencies and amplitudes of the peaks V, A, C, D, E, F and O were compared. The results revealed that there is a statistically significant difference (p < 0.05) in the latency of peak V (F(1,32) = 6.13, p < 0.05, \(\eta_{p}^{2}\) = 0.12) and peak A (F(1,32) = 4.03, p < 0.05, \(\eta_{p}^{2}\) = 0.08) between the control and experimental group. Similarly, there was a statistically significant difference seen in the amplitude of peak D (F(1,32) = 6.38, p < 0.05, \(\eta_{p}^{2}\) = 0.12) and peak F (F(1,32) = 7.97, p < 0.05, \(\eta_{p}^{2}\) = 0.15). Acknowledging how the speech signals are coded in the brainstem may aid in the timely detection and intervention of hearing-related issues, even in individuals having normal hearing acuity. The results indicate that there is damage at the level of the brainstem which will lead to poor speech understanding in those who are exposed to occupational noise. These indicators are present even before routine audiometry indicates a hearing loss.
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