I.
Introduction
II. Health effects of noise
exposure
III.
Measuring noise
IV. Methods of noise control
V. Role of the
health and safety representative
Not all sound is noise —
noise is sound that people do not like. Noise can be annoying and it can
interfere with your ability to work by causing stress and disturbing your
concentration. Noise can cause accidents by interfering with communication and
warning signals. Noise can cause chronic health problems. Noise can also cause
you to lose your hearing.
Hearing loss from exposure
to noise in the workplace is one of the most common of all industrial diseases.
Workers can be exposed to high noise levels in workplaces as varied as
construction industries, foundries and textile industries. Short-term exposure
to excessive (too much) noise can cause temporary hearing loss, lasting
from a few seconds to a few days. Exposure to noise over a long period of time
can cause permanent hearing loss. Hearing loss that occurs over time is not
always easy to recognize and unfortunately, most workers do not realize they are
going deaf until their hearing is permanently damaged. Industrial noise exposure
can be controlled — often for minimal costs and without technical difficulty.
The goal in controlling industrial noise is to eliminate or reduce the noise at
the source producing it.
Points to remember | |
| |
What are the health
effects of exposure to too much noise?
The health effects of noise
exposure depend on the level of the noise and the length of the exposure.
After spending a short time
in a noisy workplace, you may have noticed that you cannot hear very well and
you have a ringing in your ears. This condition is called temporary threshold
shift. The ringing and the feeling of deafness normally wear off after you
have been away from the noise for a short time. However, the longer you are
exposed to the noise, the longer it takes for your hearing to return to
“normal”. After leaving work, it may take several hours for a worker's ears to
recover. This may cause social problems because the worker may find it difficult
to hear what other people are saying or may want the radio or television on
louder than the rest of the family.
Suspect hearing loss if a person complains that he or she cannot hear something when you can. |
Eventually, after you have
been exposed to excessive noise for too long, your ears do not recover and the
hearing loss becomes permanent. Permanent hearing loss can never be repaired.
This type of damage to the ear can be caused by long-term exposure to loud noise
or, in some cases, by short exposures to very loud noises.
When a worker begins to
lose his or her hearing, he or she may first notice that normal talking or other
sounds, such as warning signals, are becoming unclear. Workers often adapt
themselves (“get used to”) to hearing loss produced by harmful noises at work.
For example, they may begin to read lips as people talk, but have difficulty
listening to someone in a crowd or on the telephone. In order to hear the radio
or television they may need to turn up the volume so much that it deafens the
rest of the family. “Getting used to” noise means you are slowly losing your
hearing.
It is important for you and your co-workers to be aware of signs of hearing loss. |
Hearing tests are the only
reliable way to find out whether a worker is suffering from hearing loss.
Unfortunately, hearing tests can be difficult to obtain and need to be performed
by a trained health-care professional. The reactions of new workers or visitors
to a noisy workplace can be indicators of a noise problem, for example if they
have to shout, cover their ears, or leave “in a hurry”.
In addition to hearing
loss, exposure to noise in the workplace can cause a variety of other problems,
including chronic health problems:
- Exposure to noise over a long period of time decreases coordination and concentration. This increases the chance of accidents happening.
- Noise increases stress, which can lead to a number of health problems, including heart, stomach and nervous disorders. Noise is suspected of being one of the causes of heart disease and stomach ulcers.
- Workers exposed to noise may complain of nervousness, sleeping problems and fatigue (feeling tired all the time).
- Excessive exposure to noise can also reduce job performance and may cause high rates of absenteeism.
Masking noise |
Points to remember about | |
| |
Noise in the workplace may
be disturbing because of its frequency as well as its volume. For example, a
high-pitched noise, such as a whistle, irritates the ears much more than a noise
with a low pitch, even if the volume is the same in both cases.
Sounds have different
intensities (loudness). For example, if you shout at someone instead of
whispering, your voice has more energy and can travel a great distance,
therefore it has more intensity (loudness). Intensity is measured in units which
are calls decibels (dB) or dB(A). The decibel scale is not a
typical scale — it is a logarithmic scale. Basically this means that a
small increase in the decibel level is, in reality, a big increase in the noise
level.
For example, if sound is
increased by 3 dB at any level, your ears will tell you that the sound has
approximately doubled in volume. Similarly, if sound is reduced by 3 dB, your
ears will feel that the volume has been cut in half. Therefore, an increase of 3
dB from 90 dB to 93 dB means the volume of the noise has doubled. However, a 10
dB increase at any level (for example, from 80 dB to 90 dB) means the noise
intensity has increased ten times.
Inside a typical workplace,
noise comes from different sources, such as tools (machinery and materials
handling), compressors, background noise, etc. If you want to identify all of
the noise problems in the workplace, then you must measure the noise from each
source separately. For example, if two different sources of noise in a workplace
each create 80 dB by themselves, the level of noise they make together is
83 dB (not 160 dB). Therefore when you consider the amount of noise the two
sources make together, the level of noise has doubled.
An effective way to measure
the noise in your workplace is with a sound meter. Unfortunately, it can be
difficult to get the meters and the trained personnel to use them. However,
there is a simple method that will help you to understand if there is a noise
problem in your workplace:
Simple method for
assessing noise exposure
Stand at arm's length from
a co-worker. If you cannot speak in a normal tone and have to shout to
communicate, then the noise level in your workplace is too high and should be
reduced!
|
Is there a safe level of
noise?
A safe level of noise
basically depends on two things: (1) the level (volume) of the noise; and (2)
how long you are exposed to the noise. The level of noise allowed by most
countries' noise standards is generally 85-90 dB over an eight-hour workday
(although some countries recommend that noise levels be even lower than this).
Exposure to higher noise
levels may be allowed for periods of less than eight hours of exposure time. For
example, workers should not be exposed to noise levels above 95 dB for more than
four hours per day. Exposed workers should be provided with ear protection while
exposed at this level and rotated out of the noise areas after four hours of
continuous work. Of course before using ear protection and rotation every effort
should be made to reduce noise using engineering controls.
The eight-hour per day
exposure limit found in a noise standard is the total amount of noise that a
worker may be exposed to over an eight-hour period. The exposure may be from
continuous (constant) noise, or from intermittent noise (noise
that is periodic at regular intervals but not continuous). Therefore, you must
add up the levels of noise you are exposed to throughout the day and see if they
exceed 85-90 dB. Note: workers should never be exposed to more than 140
dB of impulse noise (usually a very loud noise that occurs only once) at
any time.
The following chart gives
recommended limits of noise exposure for the number of hours exposed.
| No. of hours exposed | Sound level dB |
| 8 | 90 |
| 6 | 92 |
| 4 | 95 |
| 3 | 97 |
| 2 | 100 |
| 1.5 | 102 |
| 1 | 105 |
| 0.5 | 110 |
| 0.25 or less | 115 |
Points to remember | |
| |
How can noise be
controlled?
Workplace noise can be
controlled: (1) at the source; (2) through the use of barriers; and (3) at the
worker.
As with other types of
exposures, the best method of prevention is to eliminate the hazard. Therefore
controlling noise at its source is the best method of noise control. It can also
often be cheaper than other methods of noise control. This method of control may
require that some noisy machinery be replaced. Noise can be controlled at the
source by the manufacturer, so that noisy devices never reach your workplace.
Many machines are now required to conform to noise standards. Therefore
before new machines (such as presses, drills, etc.) are purchased, checks
should be made to see that they conform to noise standards. Unfortunately, many
used machines producing high noise levels (which have been replaced with quieter
models) are often exported to developing countries, causing workers to pay the
price with hearing loss, stress, etc.
Put a silencer on the machine instead of ear protectors on the workers. |
Noise control at the source
can also be engineered into an existing device by making adjustments to
parts or a whole machine that reduce noise. For example, the noise level from a
pneumatic drill can be reduced by placing a sound-reducing blanket around the
drill. A length of tubing on the exhaust of the drill will also reduce the noise
level. A rubber covering can be used to reduce noise from metal falling on to
metal.
Other engineering methods to reduce
noise include:
- preventing or reducing impact between machine parts;
- reducing speeds gently between forward and reverse movements;
- replacing metal parts with quieter plastic parts;
- enclosing particularly noisy machine parts;
- providing mufflers for the air outlets of pneumatic valves;
- changing the type of pump in hydraulic systems;
- changing to quieter types of fans or placing mufflers in the ducts of ventilation systems;
- providing mufflers for electric motors;
- providing mufflers for intakes of air compressors.
Noise - insulated air compressors. The principle is that the noise should be contained under the hood. The hood is made of hard material with a soft, absorbent lining. |
1.5 mm stiffened plate reduces vibrations. |
Regular maintenance,
lubrication and replacement of worn or defective parts can also be
effective ways to reduce noise levels. Noise from the way materials are
handled can be reduced by measures such as:
- reducing the dropping height of goods being collected in bins and boxes;
- increasing the rigidity of containers receiving impact from goods, or damping them with damping materials;
- using soft rubber or plastic to receive hard impacts;
- reducing the speed of conveyor systems;
- using belt conveyors rather than the roller type.
A machine vibrating on a
hard floor is a common source of noise. Mounting vibrating machines on rubber
mats or other damping material will reduce the noise problem.
If it is not possible to
control the noise at the source, then it may be necessary to enclose the
machine, place sound-reducing barriers between the source and the worker,
or increase the distance between the worker and the source. (However,
this can be difficult in many cases.) The following chart is a simple method of
knowing how much sound is reduced by distance.
If a small sound source produces a sound level of 90 dB at a distance of 1 meter, the sound level at a 2-meter distance is 84 dB, at 4 meters 78 dB, etc. |
Here are a few points to
remember when controlling noise with barriers:
- an enclosure should not be in contact with any part of the machine;
- holes in the enclosure should be minimized;
- access doors and holes for wiring and piping should be fitted with rubber gaskets;
- panels of insulating enclosures must be covered inside with sound-absorbent material;
- exhausts and air vents must be silenced and directed away from operators;
- the noise source should be separated from other work areas;
- the noise should be deflected away from work areas with a sound-insulating or reflecting barrier;
- sound-absorbent materials should be used, if possible, on walls, floors and ceilings.
Controlling noise at the
worker, by using ear protection (sometimes called hearing protection) is,
unfortunately, the most common yet least effective form of noise control.
Forcing the worker to adapt to the workplace is always the least desirable form
of protection from any hazard. Generally there are two types of ear protection:
earplugs and earmuffs. Both are designed to prevent excessive noise from
reaching the inner ear.
Earplugs are worn inside
the ear and come in a variety of materials, including rubber, plastic, or any
material that will fit tightly in the ear. Earplugs are the least desirable type
of hearing protection because they do not provide very effective protection
against noise and they can cause ear infection if pieces of the plug are left in
the ear or if a dirty plug is used. Cotton wool should not be used as ear
protection.
Earplugs and earmuffs: (1) Formable wadding-acoustical fibres; (2) Plastic-covered acoustical fibres; (3) Expandable plastics; (4) Reusable plastic earplugs; (5) Earmuffs. |
Earmuffs are more
protective than earplugs if they are used correctly. They are worn over the
whole ear and protect the ear from noise. Earmuffs are less efficient if they do
not fit tightly or if glasses are worn with them.
Ear protection is the least
acceptable method of controlling an occupational noise problem because:
- the noise is still present: it has not been reduced;
- in hot, humid conditions workers often prefer earplugs (which are less effective) because earmuffs make the ears sweaty and uncomfortable;
- management does not always provide the correct type of ear protection: often it is a case of “the cheaper the better”;
- workers cannot communicate with each other and cannot hear warning signals;
- if ear protection is provided instead of controlling the noise at source, then management is putting the responsibility on the worker — it becomes the worker's fault if he or she becomes deaf.
 |
|
| |
Health and safety representative |
Your role is to work
proactively (this means taking action before there are health or hearing
problems) to eliminate or control occupational noise exposure. Controlling noise
will help to protect workers' hearing as well as their overall health. Use the
Check-list for controlling occupational noise
at the end of this Module to help you assess noise controls in your workplace.
Other steps to help you reach your goals are:
-
Watch for early signs indicating hearing loss. Educate your co-workers so that they also can look for warning signs.
-
Work with your union and the employer to get the noise levels in your workplace measured. Noise monitoring is an effective way to find out the precise levels of noise and the sources of noise in the workplace. (Unfortunately, a sound meter and the trained personnel to use it can be difficult to get. Your local factory inspectorate may be able to measure the noise at your workplace.)
-
Try to obtain any results of the noise monitoring and compare the results with your country's noise standards (if they exist).
-
If your country does not have a noise standard then try to work with your employer to reach the lowest possible decibel level in the workplace. Work with your union to put pressure on your government to develop a noise standard.
-
Conduct the simple method for assessing noise exposure: Stand at arm's length from a co-worker. If you cannot speak in a normal tone and have to shout to communicate, then the noise level in your workplace is too high and should be reduced.
-
Work with the union and the employer to eliminate noise hazards.
-
Where noise cannot be eliminated, work with the union and the employer to engineer noise reduction at the source. This may be cheaper than buying ear protectors for everyone. If source reduction is not possible, then barriers should be used. Workers exposed to noise levels of 95 dB should wear ear protectors and be rotated after no more than four hours of continuous work at this noise level. (It is important to make sure employers do not expose workers to noise levels of 95 dB for more than four hours per day.)
-
Providing workers with ear protection is the least acceptable method of noise control. However, if this is the only solution, then earmuffs are a better choice than earplugs. Try to read the packages of various types of ear protectors to find out the level of protection they will provide. Discuss this information with your employer before he or she purchases the ear protectors. Workers should be trained in the proper use of, and the importance of wearing, their ear protectors. Try to get agreement from the employer to eliminate noisy machinery by a specified date.
-
If possible, have extra ear protectors available in the workplace to protect workers in case they forget or lose their own ear protectors.
-
Areas where ear protectors must be worn should be marked clearly, using symbols showing the need for ear protectors. For these areas, try to develop non-verbal ways of communicating so workers can still receive warning signals in case of danger.
-
Pay attention to new workers or visitors — their responses may indicate that there is a noise problem in your workplace.
-
Conduct a workplace survey asking your co-workers about problems with noise in their work areas. List the various health problems that can be caused by noise and ask workers if they experience any of these. Information about health problems may help you to identify excessive noise exposures.
-
If possible, try to have regular hearing tests provided for workers exposed to excessive noise. Some unions have negotiated hearing tests as part of their collective agreements.
|
No comments:
Post a Comment