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Objective: We tested middle-ear functioning in humans following intense exposure to noise. Noise generated by small caliber firearms was thought to have no effect on the middle-ear.Design: A cross-over design. We measured middle-ear impedance, acoustic reflex, distortion product otoacoustic emissions (DPOAEs), and transient evoked otoacoustic emissions (TEOAEs) before and after practice rounds performed twice per day.Study sample: Fifty-nine soldiers equipped with earplugs undergoing regular training for a special mission. The mean noise exposure (LAeq8h) was estimated to be 106 ±1 dB SPL.Results: Impedancemetry revealed a significant increase in the compliance and gradient of the tympano-ossicular chain after impulse noise exposure in the right and left ears. Acoustic reflex reactivity did not show a significant change. DPOAEs and TEOAEs were slightly decreased at 2 kHz, and showed a marked asymmetry in disfavor of the left ear. In soldiers with initial high reactivity of acoustic reflex, increased compliance was associated with a significant decrease in left TEOAEs at 1.5 and 2 kHz.Conclusion: Our results suggest that the use of small-caliber firearms, even while wearing earplugs, affects middle-ear function and may play a role in the early stage of auditory fatigue encompassing tinnitus. [ABSTRACT FROM AUTHOR]

The goal of this study was to examine the effect of race and gender on transient evoked otoacoustic emission (TEOAE) characteristics. TEOAE amplitude, noise levels, and hearing thresholds were compared in 81 Caucasian (mean age: 27.8 years) and 81 Chinese (mean age: 24.7 years) young adults with normal hearing. TEOAE amplitude was significantly higher in females than males and in the Chinese group than the Caucasian group. Females had better hearing sensitivity than males consistent with TEOAE results. Hearing sensitivity was not statistically different between the two racial groups; however, the interaction between race and hearing thresholds was significant. As the noise levels between the two racial groups were not statistically different, the observed differences are most likely related to differences in middle-ear transmission properties or to differences in cochlear mechanisms. Documentation of gender and racial differences and understanding the underlying mechanism of these differences will not only assist us in understanding how TEOAE will be affected by middle-ear transmission properties but also will help us in establishing normative data in clinical settings. [ABSTRACT FROM AUTHOR]