Narrow-band chirp and tone burst auditory brainstem response as an early indicator of synaptopathy in industrial workers exposed to occupational noise.

This study aims at characterizing and comparing the findings of auditory brainstem response (ABR) using narrow-band chirp (NB-chirp) and tone burst (TB) for both latency and amplitude parameters among those exposed to occupational noise and to determine which among the two serves as a better indicator of noise-induced cochlear neuropathy. Forty adult males in the age range of 20-35 years were considered, wherein 20 of them were exposed to noise > 80 dB (A) for 8 hours per day constituting Noise-exposed group; and Control group consisted of 20 individuals without occupational noise exposure. ABR was recorded using NB-chirp and TB for four frequencies at 80 dB nHL through Etymotic Research - 3A (ER-3A) Insert phones using Interacoustics Eclipse EP-25 in individuals with and without noise exposure. MANOVA was performed to compare between TB ABR and NB-chirp ABR between the two groups. Statistical analysis revealed a notable difference for NB-chirp comparisons between the two groups at three frequencies: 500 Hz, F(1, 38) = 10.6; 1000 Hz, F(1, 38) = 7.91; and 2000 Hz, F(1, 38) = 6.64. Whereas, the difference was evident at only 500 Hz: F(1, 38) = 4.98 in case of TB ABR. However, there was no significant difference seen at any of the frequencies for amplitude parameters in both TB and NB-chirp ABR. Latency of wave V using NB-chirp was considered to be a better indicator compared to TB, acting as a better clinical tool in early identification, diagnosis, and monitoring of noise induced hearing loss (NIHL).