Detecting incipient inner-ear damage from impulse noise with otoacoustic emissions

Abstract

Audiometric thresholds and otoacoustic emissions (OAEs) were measured in 285 U.S. Marine Corps recruits before and three weeks after exposure to impulse-noise sources from weapons' fire and simulated artillery, and in 32 non-noise-exposed controls. At pre-test, audiometric thresholds for all ears were <or=25 dB HL from 0.5 to 3 kHz and <or=30 dB HL at 4 kHz. Ears with low-level or absent OAEs at pre-test were more likely to be classified with significant threshold shifts (STSs) at post-test. A subgroup of 60 noise-exposed volunteers with complete data sets for both ears showed significant decreases in OAE amplitude but no change in audiometric thresholds. STSs and significant emission shifts (SESs) between 2 and 4 kHz in individual ears were identified using criteria based on the standard error of measurement from the control group. There was essentially no association between the occurrence of STS and SES. There were more SESs than STSs, and the group of SES ears had more STS ears than the group of no-SES ears. The increased sensitivity of OAEs in comparison to audiometric thresholds was shown in all analyses, and low-level OAEs indicate an increased risk of future hearing loss by as much as ninefold.

Efficacy and safety of N-acetylcysteine in prevention of noise induced hearing loss: A randomized clinical trial

“…While a 10e11% rate of STS from noise exposure during recruit training is the norm (Marshall et al, 2009), our study population exhibited a greater than 37% rate of STS despite strict use of HPDs and a highly controlled environment free of other significant noise outside the weapons training period. The most likely reason for this high rate of threshold shift is that, in addition to the standard audiometric frequencies tested in other studies (Marshall et al, 2009), this study also measured hearing thresholds at high frequencies between 2 kHz and 20 kHz, inclusive.…”

Otoacoustic-emission-based medial-olivocochlear reflex assays for humans

“…However, ears in this category are already known to be more at risk for incipient NIHL from both continuous-noise and impulse-noise sources (Lapsley Miller et al, 2006;Job et al, 2009;Marshall et al, 2009). Our working presumption is that these low-level OAEs are due to subclinical damage to the inner ear that has not yet shown a significant change on an audiogram.…”

Factors Influencing Use of Hearing Protection by Trumpet Players

“…It is thus interesting to speculate that a simple test of aural-distortion judgments might provide some indication of the ear's susceptibility to hearing damage from noise exposure. In a recent report, Marshall et al (2009) found evidence that high-frequency otoacoustic emission levels may be correlated to differences in susceptibility to hearing damage. It is tempting to assume that the same intermodulation-distortion mechanism in the mechanics of the cochlea produces audible harshness at high sound levels and measurable otoacoustic emissions at lower sound levels.…”