1. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama

2. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Hearing Loss Among Soldiers Exposed to Impulses William A. Ahroon, Ph.D. Melinda M. Hill, Au.D. National Hearing Conservation Association 35 th Annual Hearing Conservation Conference February 25-27, 2010 Orlando, Florida

3. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama ***Disclaimer*** The views, opinions, and/or findings contained in this report are those of the authors and should not be construed as an official Department of the Army position, policy, or decision, unless so designated by other official documentation. Citation of trade names in this report does not constitute an official Department of the Army endorsement or approval of the use of such commercial items. ***Preliminary Findings***

4. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Damage Risk Criteria Damage risk criteria specify: –Likelihood of a specific type of injury (or proportion of population to be protected) –Limit not-to-exceed to prevent the injury

5. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Damage Risk Criteria Example Impulsive Noise Likelihood or Proportion of Exposed Individuals –US Army Human Engineering Laboratories (1965) – 75% –Rice and Coles (1965) – 90% –Coles, Garinther & Hodge (1968) – 75%, 90% –CHABA (1968) – 95% (  MIL-STD-1474) Limit not-to-exceed: –140 dB peak SPL

6. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama DRC for Impulses – MIL-STD-1474D

7. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama DRC for Impulses – MIL-STD-1474D Hearing Protection CurveNoneSingle (plugs or muffs)Double (plugs and muffs) W--------------------- unlimited --------------------- X02,00040,000 Y01002,000 Z05100 Table 1. The daily maximum number of rounds permitted by MIL-STD-1474D Daily maximum number of rounds permitted by MIL-STD-1474D

8. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama DRC for Impulses – MIL-STD-1474D MIL-STD-1474D Free-field Exception a.The weapon is to be fired in the open. b.The pressure-time history contains at most two significant peaks, an incident pressure peak which may be followed by a ground-reflected peak. Only peaks within 50% of the highest peak will be considered significant. c.The A-duration is between 2 and 6 ms. d.The B-duration is less than 60 ms. Number of Rounds Peak Level Peak Pressure A-impulse 6190 dB65 kPa73 kPa ms 100187 dB45 kPa50 kPa ms

9. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Regulatory Documents DoD: DoDI 6055.12 Army: DA PAM 40-501 Air Force: AFOSH STD 48-20 (to be AFI 48-20) Navy: OPNAVINST 5100.23F, OPNAVINST 5100.19E, NEHC TM 6260.99 Marine Corps: MCO 6260.1E

10. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Noise Exposure Damage Risk Criteria No unprotected continuous noise exposures in excess of 85 dBA for 8 hours –DoD: Action level is 85 dBA 8-hour TWA, 3 or 4 dB time-intensity rule –Army, Air Force: Action level is 85 dB 8-hour TWA, 3 dB time intensity rule –Navy: Action level is 84 dBA 8-hour TWA, 4 dB time- intensity rule No unprotected impulsive noises in excess of 140 dB peak SPL

11. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Question: How are we (the Army) doing?

12. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Infantrymen & Indirect Fire Infantrymen

13. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Cannon Crewmember

14. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Special Forces Weapons Sergeant

15. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Cavalry Scout

16. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Combat Engineer & Heavy Const Equip Oper

17. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Mechanics

18. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Mechanics & Repairers

19. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Ammunition & EOD Specialists

20. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Summary

21. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Land Warrior Training (Rangers)

22. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Land Warrior Training Special Forces Training

23. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama US Navy Seals

24. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Question: How are we (the Army) doing?

25. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Question: How are we (the Army) doing? Answer: Not good enough.

26. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama The Army Hearing Program Success: A Great Start

27. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama Conclusions & Recommendations Continue to aggressively implement the Army Hearing Program. Demonstrate to the Army leadership the clear operational advantages provided by protecting hearing. Convince the Soldier of the survivability and performance benefits of using tactical hearing protection and enhancement systems. –Train, Train, Train  Train as you fight. Now is not the time to relax hearing conservation efforts or noise health hazard assessment methods.

28. Medical Research and Materiel Command U.S. Army Aeromedical Research Laboratory Fort Rucker, Alabama