Middle-Ear Muscle Contraction Measurements Reveal No Anticipatory Activation Prior to Live Rifle Fire

Details

• Personal Author:
  Ahroon WA ; Akins ER ; Deiters KK ; Flamme, Gregory A. ; Jones HG ; Milam LS ; Murphy, William J. ; Smith MV ; Tasko SM
• Description:
  Repetitive exposure to high-level acoustic impulses, such as those from small arms fire and blast overpressure, increases the susceptibility for hearing loss. Currently, the United States Department of Defense acquisition standard (MIL-STD-1474E) mandates the U.S. Army use the Auditory Hazard Assessment Algorithm for Humans (AHAAH) for calculating impulse noise exposure limits of military systems. However, several concerns involving the appropriateness of including this model as a medical standard in an updated Damage Risk Criteria (DRC) have been raised, and thus there is still no such medical standard available in the Department of Defense. The current study addressed a concern raised about the middle-ear muscle contraction (MEMC) associated with the acoustic reflex that is assumed, and implemented, as a protective mechanism for certain instances in which a person is "warned" prior to the impulse. Accordingly, some Damage-Risk Criteria (DRC) for impulsive noise include MEMCs as a protective factor, either as acoustic reflexes or as an early MEMC engaged in anticipation of a known imminent exposure. DRC inclusion assumes that MEMCs are pervasive ( > 95 % confidence of > 95% prevalence) within the population, and are of sufficient strength and duration to serve as a protective mechanism. For the purpose of a health hazard assessment, an inappropriate implementation of this assumption would result in an underestimation of auditory hazard and may incorrectly predict that some high-level exposures are safe. This assumption was addressed by attempting to condition an anticipatory MEMC in both laboratory and field environments. Five different training tasks were administered under laboratory-controlled conditions using both acoustic and non-acoustic elicitors. Results found the likelihood of observing an MEMC for short-duration acoustic stimuli was much lower than for non-acoustic stimuli, and that voluntary eye closure produced the greatest likelihood of an MEMC. Conditioned MEMC responses were far below the 0.95 criterion necessary to consider the responses pervasive. Interestingly, participant attention greatly influenced the likelihood of observing an early conditioned MEMC. Field measurements were made in Soldiers firing military rifles for situations where they were instructed to fire and when they had no knowledge of when a second person was firing. Results indicate that MEMC do not reliably contract either in anticipation of, or in response to, an impulsive noise. Collectively, these studies indicate MEMCs should not be included as a protective factor in DRC for impulsive noise not should it be used as an acquisition standard without substantial revision. [Description provided by NIOSH]
• Subjects:
  Hearing Loss Hearing Loss, Noise-Induced Noise Noise, Occupational Occupational Health Safety
• Keywords:
  Acoustics Acoustic Trauma Firearms Hearing Loss Impulse Noise Military Personnel Noise Exposure Physiological Effects
• ISSN:
  0742-3152
• Publisher:
  Association for Research in Otolaryngology
• Document Type:
  Text
• Genre:
  Abstract or Summary
• Place as Subject:
  Alabama ; California ; Michigan ; Ohio ; OSHA Region 3 ; OSHA Region 4 ; OSHA Region 5 ; OSHA Region 9 ; Virginia
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DFSE - Division of Field Studies and Engineering
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  43
• NIOSHTIC Number:
  nn:20060892
• Citation:
  Abstr Midwinter Res Meet Assoc Res Otolaryngol 2020 Jan; 43:107
• Federal Fiscal Year:
  2020
• Peer Reviewed:
  False
• Source Full Name:
  Abstracts of the 43rd Midwinter Research Meeting of the Association for Research in Otolaryngology, January 25-29, 2020, San Jose, California
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:89cdf4b21766e07e938d821cbcd5dbce753fada721fec7af863e722fdad8d45944afa621a1d452aa443e3e38c90ceb81cbb9595887edbcffd180a6653c6d2e76
• Download URL:
  https://stacks.cdc.gov/view/cdc/224664/cdc_224664_DS1.pdf
• File Type:
  [PDF - 1.73 MB ]