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EFFECT OF NOISE ON AIRWARRIORSINTRODUCTION
1. Noise is defined by the World Health Organization (WHO) as
unwanted sound. Physically, there is no difference between sound
and noise. The difference is one of human perception and is subject
to individual variability. The significant aspect of noise is that
it is always present in varying degrees of the environment and
especially in aviation related activities.
2. In the modern world, particularly in urban environments,
noise pollution is an everyday occurrence. This isnt to say we
should, or do, resign ourselves to its presence. In the majority of
cases noise is an annoyance and inconvenience affecting peoples
quality of life, but it can have some direct and indirect health
effects, such as damage to hearing and increased hypertension. This
paper will explore these potential effects.AIM
3. Recognising that there is still no firm consensus on how to
approach issues around aircraft noise, the paper intends to
identify certain areas, including noise assessment, compensation
schemes, and the concept of noise envelopes for which the work
needs to be undertaken.4. This paper aims to provide a view of
existing research and literature onaircraft noise, and to explain
various noise hazards, which an aviation professional is exposed
to, and propose precautionary measures and other noise control
programmes which could be implemented.
NOISE5. The term noise refers to a sound, especially the one,
which is noticeably unpleasant, or too loud. In other words, the
noise is any unwanted or annoying sound. Categorising a sound as
noise can be very subjective. For example, loud rock music can be
described as an enjoyable sound by some and at the same time
described as noise by others.
SOURCES OF NOISE
6. It goes without saying that the aircraft is the chief source
of noise when it comes to the field of aviation. However this does
not imply that there may not be other significant noise producing
hazards on the tarmac. The PA systems, vehicles plying around the
aircraft, especially some specialist vehicles of Russian origin,
all contribute to the noisy environment we find ourselves in.7.
However, the way noise decays is influenced by a large number of
factors,
such as obstructions and ground cover, which can be particularly
effective at decaying noise from ground sources. With noise from
elevated sources, such as aircraft noise, these features generally
provide no benefit. Weather conditions can also affect how noise
travels. There is more noise downwind from a source than the
equivalent location upwind (everything else being equal), and
different levels of temperature can also affect noise
propagation.
8. Figure 1 shows noise maps from road, rail and air sources. As
can be seen,
noise from road and rail is very intense around source and is
quickly dissipated by buildings and other obstructions surrounding
it. On the other hand aircraft noise disperses more slowly, for the
reasons mentioned above.
9. Therefore, the aviation environment is characterised by
multiple sources of noise both on ground and in the air. Exposure
of aircrew and ground crew to loud noise is an issue since the
beginning of aviation and has been a prevalent problem ever since.
Noise is produced by aircraft equipment, engine, transmission
systems, jet exhausts, propellers, rotors, hydraulic and electrical
actuators, cabin conditioning and pressurisation systems, cockpit
advisory and alert systems, and communication equipment, etc.
ROAD
RAIL
AIR
MEASUREMENT OF NOISE
10. Sound or noise, is produced by waves of compression and
rarefaction set up
in a medium by a vibrating body. The intensity of the sound is
measured in terms of pressure exerted by the sound energy. It is
expressed in terms of decibel (Db) units.
TYPES OF NOISE11. Steady. Continuous noise of sudden or gradual
onset and long duration (more than 1 second). Examples: Aircraft
power plant noise, propeller noise inside or outside the cockpit
etc. According to the Occupation Safety and Health Administration
of USA, the maximum permissible continuous exposure level to steady
noise in a working environment is 90 dB for 8 hours.
12. Impulse/Blast. Noise pulses of sudden onset and brief
duration (less than 1 second) that usually exceed an intensity
limit of 140 dB. Examples: Gunshot, firecracker detonation,
backfiring of a piston engine, high volume squelching of the radio
equipment and sonic boom. The eardrum may be ruptured by intense
levels (140 dB) of impulse/blast noise.
EFFECTS OF NOISE
13. Most noise impacts are quite localised, affecting those
closest to its source but causing much less of an impact on those
further away. This is because the level of noise decays as distance
from the source increases.
14. In recent years the effects of noise pollution have become
better recognised and understood. Large scale European studies such
as ANASE, RANCH and HYENA have researched how the population as a
whole, and individuals in particular, can be affected by noise.
15. For the purpose of this paper it is helpful to conceptualise
the effects of noise by considering them in three groups: health
effects, amenity effects and productivity and learning effects
EFFECTS OF NOISE ON HEARING
16. Whenever our ears are exposed to loud noise the hearing
mechanism is over simulated and soon becomes fatigued. Once the
exposure to loud noise is stopped the ear gradually recovers from
fatigue. Hearing is impaired during the fatigued stage but becomes
normal when the fatigue disappears. This is temporary hearing loss
induced by noise.
17. When exposure to loud noise occurs daily as a routine, the
ability of the ears to recover quickly from fatigue is lost and
ultimately this hearing loss becomes permanent. This initially
affects the high frequencies and later on low frequencies, such as
the spoken word, are also affected.PHYSICAL EFFECTS
18. Ear discomfort. Ear discomfort may occur during exposure to
a 120 dB or a louder noise, for a shorter duration (in hours).19.
Ear pain. Ear pain may occur during exposure to a noise of the
level of 130 dB. This occurs due to eardrum being functional close
to its rupture limits.20. Eardrum Rupture. Eardrum rupture may
occur during exposure to a 140dBintensity of sound. This is due to
intensity of sound being more that the tolerance of eardrum.21.
Temporary Hearing Impairment. Unprotected exposure to loud,
steady
noise above 90dB for a short duration, even several hours, may
cause a hearing impairment temporarily. The hearing normally
returns to normal within several hours following cessation of the
noise exposure.PSYCHOLOGICAL EFFECTS.
22.Subjective effects. Annoying high intensity noise can cause
distraction, fatigue, irritability, startle responses, sudden
awakening and poor sleep quality, loss of appetite, headache,
vertigo, nausea and impaired concentration and memory loss.
22. Speech interference. Loud noise can interfere with or mask
normal speech, making it difficult to understand.
24. Performance. Noise is a distraction and can increase the
number of errors on any given task. Task that requires vigilance,
concentration, calculations, and making judgements about time can
be adversely affected by exposure of loud noise higher than 90
dB.CONCLUSION23. When the ears are exposed suddenly to very loud
noise or blast, the hearing mechanism being very delicate, suffers
severe damage from which complete recovery is often not possible.
This leads to residual hearing loss which is permanent. It will be
incorrect to say that the human ear gets used to a certain level of
noise during the daily routine. Actually this is one of the signs
of beginning of noise induced hearing loss, when the loud noise
does not hurt the ear so much.
24. Since the damage caused by noise cannot be corrected by any
treatment, avoiding all unnecessary exposure to loud noise is the
best means available to us. Various aviation bodies have already
identified aircraft noise as a miscreant and have or are in the
process of adopting precautionary measures.
RECOMMENDATIONS
24. The hazardous effects of exposure to loud noise can be
minimised by either protecting your ears or by moving the source of
noise away from the inhabited area.
25. Proofing. This is an extremely effective measure which can
reduce the noise level in the working environment to a large
extent. All the working places as far as possible need to be sound
proofed where ever the aircraft are likely to be in the region of a
kilometre or so.26. Ground Run Points In many stations in IAF, the
Ground Run points are located in very close proximity to the
Operations Complex. Off late operational expediency has resulted in
the serious nature of this problem being over looked. Proper
positioning of noise deflectors and ground run points, away from
habitation would go a long way in improving the working
environment.28.Personal Protection. All personnel who are working
in close proximity to aircraft or other sources of loud noise
should use ear defenders. These attenuate the noise reaching the
ears. They are available in two forms the plug type and the muff
type. The former have been shown to be more effective however are
not widely available. Additionally, erecting signboards, to make
personnel aware off entering into Hazardous Zone due to aircraft
noise can mark the hazardous areas. If nothing else is available
plugging the ears with the fingers is as effective as anything else
in safeguarding our precious hearing.29.Monitoring of hearing. The
hearing of those exposed top loud noise on a routine basis should
have their hearing monitored at regular intervals. Any one showing
a tendency towards hearing loss should be shifted to a less noisy
environment. AF STATION JODHPUR
(Ankit Joshi)
Date Dec 14
Flt Lt
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