Abstract:
Objectives: Hidden Hearing Loss (HHL) is a type of hearing loss that affects low and mid spontaneous rate nerve fibers, while sparing normal functioning of the outer hair cell. The study investigated the effect of occupational noise exposure and to assess the relationship between individuals with and without noise exposure. The study utilized speech perception tests in presence of broadband noise (BBN), acoustic reflex thresholds (ARTs) and growth functions, and auditory brainstem responses (ABR) in both quiet and varied ipsilateral broadband noise conditions.
Methods: A standard group comparison design was employed on 60 normal-hearing participants (119 ears) in the age range of 25 to 50 years without (Group I) and with occupational noise exposure below DRC (Group II) and above DRC (Group III) levels. Speech perception tests at 0 dBSNR, ART and growth function at 500 Hz, 2000 Hz, and BBN, and ABR recordings in quiet and varied ipsilateral masking conditions (50, 70 & 90 dB SPL) to studty the effect of noise exposure on hearing. Raw scores in speech perception tests, acoustic reflex threshold, slope of reflex growth and ABR latency and amplitude measures of I and V peaks were analyzed.
Results: Results showed that noise-exposed individuals had poorer speech perception scores, elevated ART, and steeper reflex growth at 2000 Hz and BBN. ABR peak V latency shifts and peak I amplitude were significantly less in noise-exposed individuals compared to those without exposure (p<0.05), highlighting the impact of even moderate noise on suprathreshold hearing. However, no significant differences were observed for ABR latency of peak I and amplitude of peak V in all conditions (p>0.05).
Conclusions: Speech perception scores (0 dBSNR) along with ABR Peak V latency shift and peak I amplitude reduction in the ipsilateral masking paradigm, can be considered as a sensitive diagnostic tool to detect HHL.
