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Noise exposure that causes a temporary threshold shift but no permanent threshold shift can cause degeneration of synaptic ribbons and afferent nerve fibers, with a corresponding reduction in wave I amplitude of the auditory brainstem response (ABR) inanimals.This formof underlying damage, hypothesized to also occur in humans, has been termed synaptopathy, and it has been hypothesized that there will be a hidden hearing loss consisting of functional deficits at suprathreshold stimulus levels. This study assessed whether recreational noise exposure history was associated with smaller ABR wave I amplitude and poorer performance on suprathreshold auditory test measures.Noise exposure historieswere collected from 26 men and 34women with hearing thresholds ≤ 25 dB hearing loss (HL; 250 Hz to 8 kHz), and a variety of functional suprathreshold hearing tests were performed. Wave I amplitudes of click-evoked ABR were obtained at 70, 80, 90, and 99 dB (nHL) and tone-burst evoked ABR were obtained at 90 dB nHL. Speech recognition performance was measured in quiet and in competing noise, using theWords in Noise test, and the NU-6 word list in broadband noise (BBN). In addition, temporal summation to tonal stimuli was assessed in quiet and in competing BBN. To control for the effects of subclinical conventional hearing loss, distortion product otoacoustic emission amplitude, an indirect measure of outer hair cell integrity, was measured. There was no statistically significant relationship between noise exposure history scores andABRwave I amplitude in eithermen or women for any of the ABR conditions. ABR wave I amplitude and noise exposure history were not reliably correlated with suprathreshold functional hearing tests. Taken together, this study found no evidence of noise-induced decreases inABR wave I amplitude or signal processing in noise in a cohort of subjects with a history of recreational noise exposure. [ABSTRACT FROM AUTHOR]

Background: There has been significant discussion in the literature regarding music player use by adolescents and young adults, including whether device use is driving an increase in hearing loss in these populations. While many studies report relatively safe preferred listening levels, some studies with college student participants have reported listening habits that may put individuals at risk for noise-induced hearing loss (NIHL) if those listening habits continue over the long term. Purpose: The goal of the current investigation was to extend listening level data collection sites from urban city settings studied by others to a more rural campus setting. Research Design: This was a prospective study. Study Sample: Participants were 138 students on the University of Florida campus (94 males, 44 females), 18 years or older (mean = 21 years; range: 18-33 years). Data Collection and Analysis: In this investigation, the current output level (listening level) was measured from personal listening devices used by students as they passed by a recruiting table located in one of three areas of the University of Florida campus. One location was in an open-air campus square; the other two locations were outside the campus recreation building ("gym") and outside the undergraduate library, with participants recruited as they exited the gym or library buildings. After providing written informed consent, participants completed a survey that included questions about demographics and typical listening habits (hours per day, days per week). The output level on their device was then measured using a "Jolene" mannequin. Results: Average listening levels for participants at the three locations were as follows: gym: 85.9 ± 1.4 dBA; campus square: 83.3 ± 2.0 dBA; library: 76.9 ± 1.3 dBA. After adjusting to free-field equivalent level, average listening levels were gym: 79.7 ± 1.4 dBA; campus square: 76.9 ± 2.1 dBA; library: 70.4 ± 1.4 dBA. There were no statistically significant differences between male and female listeners, and there were no reliable differences as a function of race. After accounting for daily and weekly use patterns, 5% were deemed at risk based on the criteria put forward by the Occupational Safety and Health Administration, and 9% were deemed at risk based on the guidance provided by the National Institute for Occupational Safety and Health. Conclusions: Some 5-10% of the participants were deemed at risk; this finding is consistent with other studies using similar methods. It is possible that the same listeners would have selected different listening levels in other noise backgrounds, however. This unknown variable makes it difficult to estimate risk with a single listening level measurement. [ABSTRACT FROM AUTHOR]