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Tasks that require vigilance, concentration,
calculations, and making judgments about time
can be adversely affected by exposure to loud
noise higher than 90 dB.
HOW TO PROTECT YOUR HEARING
Limiting duration of exposure to noise. OSHAestablished
permissible noise exposure limits for the
workplace (including the cockpit of an aircraft):
Noise Exposure Level Limits
Noise Intensity
(dB)
Exposure Limit
(hrs. per day)
90 8
92 6
95 4
97 3
100 2
102 1.5
105 1
110 .5
115 .25
Use Hearing Protection Equipment. If the ambient
noise level exceeds OSHA’s permissible noise
exposure limits, you should use hearing protection
devices—earplugs, earmuffs, communication
headsets, or active noise reduction headsets. Even
if an individual already has some level of permanent
hearing loss, using hearing protection equipment
should prevent further hearing damage. These
protection devices attenuate noise waves before
they reach the eardrum, and most of them are
effective at reducing high-frequency noise levels
above 1,000 Hz. It is very important to emphasize
that the use of these devices does not interfere with
speech communications during fl ight because they
reduce high-frequency background noise, making
speech signals clearer and more comprehensible.
• Earplugs. Insertable-type earplugs offer a very
popular, inexpensive, effective, and comfortable
approach to provide hearing protection. To be
effective, earplugs must be inserted properly to
create an air-tight seal in the ear canal. The waximpregnated
moldable polyurethane earplugs
provide an effective universal fi t for all users and
provide 30 to 35 dB of noise protection across all
frequency bands.
• Communication headsets. In
general, headsets provide the
same level of noise attenuation
as earmuffs, and are also more
easily donned and removed that
earplugs, but the microphone
can interfere with the donning of
an oxygen mask.
• Active noise reduction headsets. This type of
headset uses active noise reduction technology
that allows the manipulation of sound and signal
waves to reduce noise, improve signal-to-noise
ratios, and enhance sound quality. Active noise
reduction provides effective protection against lowfrequency
noise. The electronic coupling of a lowfrequency
noise wave with its exact mirror image
cancels this noise.
• Combinations of protection devices. The
combination of earplugs with earmuffs or
communication headsets is recommended when
ambient noise levels are above 115dB. Earplugs,
combined with active noise reduction headsets,
provide the maximum level of individual hearing
protection that can be achieved with current
technology.
SUMMARY
• Hearing is second only to vision as a sensory
mechanism to obtain critical information during the
operation of an aircraft.
• All sounds have three distinctive variables:
frequency, intensity, and duration.
• Normal conversation takes place in the frequency
range from 500 to 3,000 Hz.
• Daily exposure to noise levels higher than 90dB
can cause hearing impairment. This can go
unnoticed initially because it occurs in the vicinity
of 4,000 Hz (outside the conversational range)
• If the ambient noise level reaches 90dBA, you
4
must use hearing protection equipment to prevent
hearing impairment.
• Exposure to loud noise before fl ying (at home,
while driving, at a party, etc.) can be as harmful as
exposure to aircraft noise.
MEDICAL FACTS FOR PILOTS
Publication: AM-400-98/3
Written by: Melchor J. Antuñano, M.D.,
and James P. Spanyers
Prepared by: FAA Civil Aerospace Medical Institute
Aeromedical Education Division
AAM-400, P.O. Box 25082
Oklahoma City, OK 73125
Other Pilot Safety Brochures Available
Number Title
AM-400-94/2 Alcohol and Flying: A Deadly
Combination
OK05-0270 Carbon Monoxide: A Deadly Threat
AM-400-03/2 Deep Vein Thrombosis and Travel
AM-400-91/1 Hypoxia: The Higher You Fly, the Less
Air...
AM-400-97/1 Introduction to Human Factors in Aviation
AM-400-92/1 Over the Counter Medications and Flying
AM-400-98/2 Pilot Vision
AM-400-95/1 Smoke!
AM-400-00/1 Spatial Disorientation: Visual Illusions
AM-400-03/1 Spatial Disorientation: Why You Shouldn’t
Fly By the Seat of Your Pants
AM-400-01/1 Physiological Training Courses for Civil
Aviation Pilots
AM-400-05/1 Sunglasses for Pilots: Beyond the Image
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Pilot Safety Brochures飞行员安全手册(23)
