What Do We Know About Hearing Loss on Aircraft Carriers

1
What Do We Know About Hearing Loss on Aircraft
Carriers?

• Lynne Marshall, Ph.D.
• Naval Submarine Medical Research Laboratory
• 4-25-01

2
Hearing Loss on Aircraft Carriers

• STS vs. TTS vs. PTS vs. HL
• Summary of Audiological Studies
• Summary of Additional Questions Raised

3
STS vs. TTS vs. PTS vs. HL

• STS - Navy Definition
• Change in measured hearing thresholds, but dont
  know why.
• Could be due to test-retest variability, TTS, or
  PTS.
• STS - Empirical Definition
• Change in measured hearing thresholds relative to
  non-noise-exposed control group.
• Most likely due to TTS or PTS.
• TTS
• If no TTS from work exposure, there will be no
  PTS.
• Difficult administratively to obtain in
  operational environments.

4
STS vs. TTS vs. PTS vs. HL (cont)

• PTS
• In the Navy, PTS is determined by repeated
  measurements and audiological evaluation.
• Depends on a valid baseline measurement.
• HL
• Determines when PTS results in abnormal hearing.
• Does not depend on a valid baseline measurement.

5
Summary of Audiological Studies TTS STS

• TTS (Rovig)
• Thirty percent of flight deck personnel working
  in high-level noise(TWA-104.5) with single
  hearing protection exhibited TTS within 30
  minutes of being out of gt105dBA noise.
• Ten percent of all flight deck personnel
  exhibited TTS.
• Most people wore single hearing protection.
• STS-Navy Criteria (Bohnker)
• Navy STS rate is around 18.
• There is not agreement across studies re STS
  rate.
• STS-Empirical Criterion (Lapsley Miller)
• STS rate for aircraft carriers after one
  deployment (gt11).

6
Summary of Audiological Studies (PTS)

• Lapsley Miller
• Overall PTS rate ?4.4
• Air Engineering Reactor
• ?3.7 ? 3.1 ?6.5
• Bohnker
• Estimated annual PTS of 5-6
• Rovig
• lt4YRS 4YRS
• FD 15.4 37.8
• ENG 17.6 23.2
• ADMIN --- 11.0

7
Prevalence of Hearing Loss (gt20dB)

• Rovig
• DEPT TIME lt4YRS ? 4 YRS
• FD Base 5 14
• Last 5 30
• ENG Base 12 16
• Last 15 37
• ADMIN Base --- 5
• Last --- 5
• Bohnker Engineering enlisted rates had a higher
  prevalence of hearing loss than aviation rates.
• Lapsley Miller This may not be occurring on a
  single cruise.

8
Additional Issues Raised

• Many questions could be answered by all
  hearing-conservation records immediately
  deposited into Navy database.
• Current database limitation is that it does not
  address specific jobs.
• How is TTS related to PTS?
• Who is most susceptible?

9
Individual Susceptibility

• Individual differences in susceptibility are
  real.
• Past attempts to determine who is most
  susceptible have failed.
• Current attempts include
• genetic variations
• otoacoustic emissions
• Chance of success is influenced by
• external factors (differences in noise exposure
  in hearing protection usage and effectiveness)
• internal factors (may not be static over time)