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Abstract
Objective: The objective of this study is to determine whether acoustic reflexes are pervasive (i.e. known with 95% confidence to be observed in at least 95% of people) by examining the frequency of occurrence using a friction-fit diagnostic middle ear analyser. Design: Adult participants with very good hearing sensitivity underwent audiometric and middle ear testing. Acoustic reflexes were tested ipsilaterally and contralaterally in both ears across a range of elicitor frequencies. Reflex elicitors were 700 ms tones presented at maximum level of 100 dB HL. Two automated methods were used to detect the presence of an acoustic reflex. Study sample: A group of 285 adult volunteers with normal hearing. Results: There were no conditions in which the proportion of participants exhibiting acoustic reflexes was high enough to be deemed pervasive. Ipsilateral reflexes were more likely to be observed than contralateral reflexes and reflexes were more common at 0.5 and 1 kHz elicitor frequencies as compared with 2 and 4 kHz elicitor frequencies. Conclusions: Acoustic reflexes are common among individuals with good hearing. However, acoustic reflexes are not pervasive and should not be included in damage risk criteria and health hazard assessments for impulsive noise.
Acknowledgements
The authors thank Hannah Mork, Travis Stehouwer, Lydia Roberts, Sarah Pouliot, Kelsey Bowles, Deidre Shepherd, Kyle Geda, Katherine Rothe, Madeline Smith, Meghan Smith, Macey Nacarato and Esther Ho for their extensive efforts in data collection and review. In addition, we would like to recognise Mark Stephenson (SASRAC), Nate Green (USAARL) and Heath Jones (USAARL), who contributed helpful comments on the use of MEMC in DRC. The authors also thank Doug Keefe (Boys Town National Research Hospital), Howard Hoffman (National Institute on Deafness and other Communication Disorders) and three anonymous reviewers for their comments on this manuscript.
Declaration of interest: The findings and conclusions in this report are those of the authors and do not represent any official policy of the CDC, NIOSH, US Army or US Navy. Mention of company names and products does not constitute endorsement by the CDC, NIOSH, US Army or US Navy. The authors have no conflicts to declare.
This work was supported by the U.S. Army Medical Research and Materiel Command Award number W81XWH-14-2-0140, U.S. Centers for Disease Control and Prevention/National Institute for Occupational Safety and Health contract 254-2014-M-61068, and U.S. Office of Naval Research Warfighter Performance Department agreement 14-NS-14-04.