Robert
H. Wilkinson
Michigan State University Extension
That
dull, ringing sensation in your ears after a long day on the
tractor is an indication that you have exceeded a sound level
that can be comfortably tolerated. Ringing in the ears could
be the first sign of hearing loss.
This
ringing is typically accompanied with a slight loss of hearing
where faint sounds that are normally heard are no longer detectable.
While overnight rest will generally restore normal hearing,
repeated, prolonged exposure to noise of this intensity will
likely result in a permanent hearing loss.
Research shows that safe exposure times are determined by how
loud the noise is (see Figure 1). Keeping below this noise exposure
limit can protect the hearing of most individuals at a given
sound level.
For
instance, the decibel level inside an acoustically-insulated
tractor cab performing typical field operations is 85 decibels
(see Table 1). At this sound level, there is no threat of
hearing damage for most individuals, regardless of the length
of time in the cab. But, take off the cab, let corrosion deteriorate
the exhaust system, and now this same tractor is producing
100 decibels. These 15 additional decibels limits safe operation
to two hours before the threat of hearing damage becomes an
issue. Older tractors without cabs frequently produce sound
levels that allow less than eight hours of exposure before
noise induced hearing loss is a problem.
Table 1. Decibel levels of common sounds
at typical distance from source.
0
| Acute threshold of hearing
|
15
| Average threshold of hearing
|
20
| Whisper
|
30
| Leaves rustling, very soft
music
|
40
| Average residence
|
60
| Normal speech, background
music
|
70
| Noisy office, inside auto
at 60 mph
|
80
| Heavy traffic, window air-cond.
|
85
| Inside acoustically insulated
protective tractor cab in field
|
90
| OSHA limit - hearing damage
on excess exposure to noise above 90 dB
|
100
| Noisy tractor, power mower,
ATV, snowmobile, motorcycle
|
120
| Thunder clap, jack-hammer,
basketball crowd, amplified rock music
|
140
| Threshold of pain - shot
gun, near jet taking off, 5- hp siren (100')
|
In many instances, it is not possible to reduce tractor or
equipment noises below the safe 85 decibel limit established
by the National Institute for Occupational Safety and Health,
a federal government research agency. In these situations,
the only choice is to use ear plugs or earmuffs.
Disposable
ear plugs are the least expensive method of ear protection.
Quantity discount prices begin at 15 cents a pair. Earmuff
prices begin at about $10.
These
protective devices have a noise reduction rating (NRR) which
is an indicator of how many decibels a hearing protector reduces
noise.
Ear
plugs have an NRR ranging from 26 to 31; most earmuffs have
a NRR ranging from 23 or more. In the example of a tractor
producing 100 decibels, an operator wearing ear plugs can
reduce his or her noise level exposure to less than 80 decibels.
Noise
induced hearing loss knows no age discrimination; older workers
as well as teenagers have suffered hearing loss from farm-related
activities. Even workers who have suffered some hearing loss
can save what they have left with consistent use of ear plugs
or muffs when working around noisy equipment.
"If
you can't reduce the noise level of machinery, block it out
with hearing protection devices" is sound advice for anyone
working around noisy equipment. In addition to wearing ear
protection, the following recommendations will help keep noise
levels down:
Blocking
noise can lower the potential for hearing losses. This includes
simple machinery maintenance techniques such as keeping all
equipment well-lubricated, properly adjusted, and maintained.
Maintenance can increase the lifespan of equipment, reduce
down time, create safer working conditions, and can reduce
noise.
Limit
exposure to the noise. The risk of hearing damage increases
with the amount of time spent in a noisy area. Limiting the
amount of time spent in a noisy area reduces the risk of hearing
damage. If you can't reduce exposure, wear earmuffs or rated
ear plugs. Cotton makes a great T-shirt, but it is ineffective
as ear plugs.
When
working in a shop, keep as much distance between you and noisy
equipment. Locate a noisy air compressor or other shop equipment
as far away from the work area as possible. Doubling the distance
from the source of a noise reduces the sound level by one-fourth
(1/4). An acoustic barrier, made out of fire resistant material,
could also reduce the noise level in a shop.
When
purchasing new equipment, consider the noise output level
of the machine. The additional cost of purchasing a tractor
with a cab may be outweighed by the increased benefits of
reduced noise and operator comforts. Sound levels inside the
cab of a new tractor are often listed in the manufacturer's
literature. Lowering noise levels in the tractor cab is an
indication of quality construction for "comfort of the operator"
and can avoid hearing loss.
Disclaimer
and Reproduction Information: Information in NASD does not
represent NIOSH policy. Information included in NASD appears
by permission of the author and/or copyright holder. More
NASD Review: 04/2002
This
information is for educational purposes only. Reference to
commercial products or trade names does not imply endorsement
by the Cooperative Extension Service or bias against those
not mentioned. Cooperative Extension Service programs are
open to all without regard to race, color, national origin,
sex or handicap. MSU is an Affirmative Action/Equal Opportunity
Institution.
|