Estimated dose-response relationship between impulse noise exposure and temporary threshold shift in tactical training environments

Impulse noise and repetitive low-level blast exposure are routine occupational risks for certain populations of military and law enforcement personnel, yet the effects on human hearing are not fully understood. This study evaluated the hearing of 214 service members before and after tactical exercises using boothless audiometers in the field. Training involved weapons systems that generated high levels of impulse noise measured with wearable dosimeters. The impulse waveforms were analyzed to predict the probability of temporary threshold shifts (TTSs) based on various risk criteria. The L_Aeq,8h predicted TTS events with 64% accuracy (receiver operating characteristic area under the curve = 0.70) on held-out participants using leave-one-out cross-validation. Adding kurtosis improved accuracy to 66% (receiver operating characteristic area under the curve = 0.75). Peak sound level and the Auditory Hazard Assessment Algorithm for Humans model were substantially less accurate predictors of TTS events. A dose-response curve generated using logistic regression indicated a greater likelihood of TTS with increasing cumulative noise exposure. These findings support the use of energy-based auditory risk criteria for impulse noise. However, additional validation data are needed to determine the quantitative risk of short- and long-term hearing damage associated with a given level of impulse noise exposure.