Effects of Aging Versus Noise Exposure on Auditory System in Individuals With Normal Audiometric Thresholds.

BACKGROUND: The study aims at investigating the effect of aging and noise exposure on the auditory system using auditory brainstem responses (ABRs), distortion product otoacoustic emissions (DPOAEs), and contralateral suppression of OAEs (CSOAEs). The objective was to compare DPOAEs, CSOAEs, and ABR in aged and noise-exposed individuals with the normal, to find an indicator for early diagnosis of auditory damage. METHODS: Sixty adult male participants were divided into 3 groups. Group 1 included individuals not exposed to occupational noise and group 3 included individuals exposed to occupational noise who were <35 years of age. Group 2 consisted of individuals with an age range of 45-65 years without any occupational noise exposure. DPOAE fine structure was studied at 8 points per octave at different F2 frequencies. Transient evoked otoacoustic emissions (TEOAEs) were measured with and without contralateral broad band noise (BBN) at 30 dB SL (CSOAEs). ABR was recorded using click stimuli at different levels, from 90 dB nHL down to 50 dB nHL. The absolute amplitude and peak latencies for peaks I, III, and V; and the wave V/I amplitude ratio were analyzed. RESULTS: In CSOAEs, group 1 showed greater contralateral suppression when compared to group 2 and group 3. The amplitude of ABR wave I and the wave V/I ratio showed a significant difference between the 3 groups, and there was a reduction in amplitude of wave I for groups 2 and 3. CONCLUSION: The findings indicate that the functioning of the auditory system is affected by occupational noise exposure and aging. CSOAEs, ABR wave I amplitude, and wave V/I amplitude ratio serve as reliable markers in the identification of hidden hearing loss.

Feasibility of objective assessment of difference limen for intensity using acoustic change complex in children with central auditory processing disorder.

INTRODUCTION: Acoustic change complex (ACC) shows brain's ability to discriminate between acoustic features in an ongoing stimulus. It is this nature of ACC that has generated interest in studying the usefulness of ACC as an objective tool for evaluating difference limens for various stimulus parameters. The present study therefore aimed at investigating the utility of ACC as an objective measure of difference limen for intensity (DLI) in normal hearing children with and without (C)APD. METHODS: Fifteen children with (C)APD and 15 normal hearing children in whom (C)APD was ruled out (comparison group) in the age range of 8-12 years underwent ACC for 6 intensity differences (+1, +3, +4, +5, +10 & +20 dB) and a standard stimulus using a 1000 Hz stimulus. RESULTS: Behavioral DLI (DLIb) as well as DLI found using ACC (DLIo) were both significantly larger in children with (C)APD than the comparison group (p < 0.05). Further, there was a significantly strong positive correlation between DLIb and DLIo (p < 0.001]. CONCLUSION: Outcome of the study provides evidence for the clinical use of ACC as an objective tool for examining DLI in children with (C)APD.

Utility of Acoustic Change Complex as an Objective Tool to Evaluate Difference Limen for Intensity in Cochlear Hearing Loss and Auditory Neuropathy Spectrum Disorder.

Purpose This study aimed to investigate usefulness of acoustic change complex (ACC) as an objective measure of difference limen for intensity (DLI) in auditory neuropathy spectrum disorders (ANSD) and cochlear hearing loss (CHL). Method The study used a multiple static group comparison research design. Twenty normal-hearing individuals (NH), 19 individuals with ANSD, and 23 individuals with CHL underwent DLI measurement using behavioral (psychoacoustic) techniques and ACC. For eliciting ACC, a 500-ms, 1,000-Hz pure tone was presented at 80 dB SPL. Additionally, six variants of this stimulus with intensity increments of 1, 3, 4, 5, 10, and 20 dB starting 250 ms after stimulus onset were used to elicit the ACC. Results The lowest intensity change that produced replicable and clearly identifiable ACC was referred as objective DLI. In comparison to NH and CHL, the behavioral as well as the objective DLI were significantly larger (poorer) in ANSD (p < .05). Significantly strong positive correlation existed between DLI obtained using behavioral and objective measures (p < .05). Conclusions ACC could be a useful objective tool to measure DLI in the clinical population, provided the individuals of the clinical population fulfill the prerequisite of the presence of Auditory Long Latency Responses. Supplemental Material https://doi.org/10.23641/asha.12560132.