Noise and Vibration Hazards
Sound
is any change in pressure that can be detected by the ear. Typically, sound is
a change in air-pressure. However, it can also be a change in water pressure or
any other pressure-sensitive medium. Noise is unwanted sound. Consequently, the
difference between noise and sound is in the perception of the person hearing
it.
Noise,
which is essentially any unwanted or undesirable sound, is not a new hazard.
Indeed, noise induced hearing loss (NIHL) has been observed for centuries.
Before the industrial revolution, however, comparatively few people were
exposed to high levels of workplace noise. The advent of steam power in
connection with the industrial revolution first brought general attention to
noise as an occupational hazard. Workers who fabricated steam boilers developed
hearing loss in such numbers that the malady was dubbed "boilermakers
disease." Increasing mechanization in all industries and most trades has
since proliferated the noise problem.
Hearing:
Hearing
is a series of events in which sound waves in the air produce electrical
signals and cause nerve impulses to be sent to the brain where they are
interpreted as sound. The ear has three main parts: the outer, middle and inner
ear. Sound waves enter through the outer ear and reach the middle ear where
they cause the ear drum to vibrate.
Figure 1. Anatomy of hearing system
Outer Ear: The visible portion of the ear forms the entrance to the ear canal
directing sound waves to the eardrum. Ear drum separates the outer ear from the
middle ear, which is a cone-shaped membrane about half-inch in diameter. The
distance the eardrum moves in response to sound pressure waves is extremely
small. (One billionth of an inch). Besides vibrating
in response to sound waves, the eardrum protects the contents of the middle
ear.
Middle Ear: The middle ear is an air-filled cavity. Its major function is to
transmit the oscillatory motion of the eardrum to the inner ear. The middle ear
contains three bones, which are the smallest in the human body: the malleus (hammer), the incus
(anvil) and the stapes (stirrup). Hammer and anvil bones vibrate as a unit in
response to sound waves. This assemblage of bones (ossicles)
transmits sound waves to the inner ear, and protects the inner ear by either
amplifying or diminishing the sound waves. In addition, there are two muscles
attached to the stapes (stirrup) and the malleus
(hammer). The function of these muscles is to tighten up the eardrum and the
motion of the three bones (ossicles), thereby
reducing the efficiency of sound transmission. This phenomenon, known as the
acoustic reflex, is carried out on command of the brain after a very loud sound
reaches the eardrum.
Inner Ear:
The inner ear is a complex system of ducts that houses the end organs for
hearing and balance. The components of the inner ear have nothing to do with
hearing but are responsible for certain senses. One component is responsible
for the sense of acceleration and gravity. Another component, which is an
arrangement of three semicircular canals, provides humans with their sense of
orientation in space and balance. The hearing part of the ear is called
cochlea. When sound waves travel through the external auditory canal, the foot
of the stapes (stirrup) bone knocks against an oval window that is a wide
opening in the cochlea, and sound is transmitted to the liquid inside. The
vibrations move through fluid in the snail-shaped hearing part of the inner ear
(cochlea) that contains the hair cells. The fluid in the cochlea moves the top
portion of the hair cells, called the hair bundle, which initiates the changes
that lead to the production of the nerve impulses. These nerve impulses are
carried to the brain where they are interpreted as sound. Different sounds move
to the population of hair cells in different ways, thus allowing the brain to
distinguish among various sounds, for example, different vowel and consonant
sounds. The round window lying just below the oval window is an elastic
membrane, which is the final component that sound reaches in the human ear.
Physical Properties of Sound:
The
effects of sound on a person depend on three physical characteristics of sound:
amplitude, frequency, and duration. Sound pressure level (SPL), expressed in
decibels, is a measure of the amplitude of the pressure change that produces
sound. This amplitude is perceived by the listener as loudness. In
sound-measuring instruments, weighting networks are used to modify the SPL.
Exposure limits are commonly measured in dBA. Most
environmental noises include a wide band of frequencies and, by convention, are
measured through the "A" filter in the sound-level meter and thus are
designated in dB(A) units.
The
frequency of a sound, expressed in Hz, represents the number of cycles
occurring in 1 sec and determines the pitch perceived by the listener. Humans
with normal hearing can hear a frequency range of about 20 Hz to 20 kilohertz
(kHz).
|
Infrasonic Frequencies |
Less than 20 Hz |
|
Normal Hearing Frequencies |
20 Hz to 20 KHz |
|
Ultrasonic Frequencies |
Above 20 KHz |
Figure 2. Infrasonic ,
ultrasonic and normal hearing frequencies
Although
no uniformly standard definitions exist, noise exposure durations can be
broadly classified as continuous-type or impulsive. All nonimpulsive
noises (i.e., continuous, varying, and intermittent) are collectively referred
to as "continuous-type noise." Impact and impulse noises are
collectively referred to as "impulsive noise." Impulsive noise is
distinguished from continuous-type noise by a steep rise in the sound level to
a high peak followed by a rapid decay. In many workplaces, the exposures are
often a mixture of continuous-type and impulsive sounds.
Figure 3.
Sound Waves
dBA = Decibel: Represents the smallest difference
in the level of sound that can be perceived by the human ear. It is a unit of
measurement used for discussing the level of sound.
Threshold of Hearing: The weakest sound that can be heard by a healthy human ear in a quiet
setting is known as the threshold of hearing which is approximately 10 dBA.
Threshold of Pain: The
maximum level of sound that can be perceived without experiencing pain is known
as the threshold of pain which is 140 dBA.
Figure 4. Decibel Levels for Different Types
of Sounds (Click on the figure above for more examples)
|
Source |
Decibels (dBA) |
|
Whisper |
20-30 |
|
Quiet Office |
50 |
|
Chain Saw |
90-110 |
|
Grinding Operations |
100 |
|
Passing Truck |
100 |
|
Jet Aircraft |
140-150 |
Industrial Noise:
Wide Band Noise: Noise that is distributed over a wide range of
frequencies. (e.g. Manufacturing machines)
Narrow Band Noise: Noise that is confined to narrow range of
frequencies. (e.g. Power tools)
Impulse Noise: Noise that is created at a transient pulse with a
single frequency pattern.
Noise-Induced Hearing Loss (NIHL):
NIHL
is caused by exposure to sound levels or durations that damage the hair cells
of the cochlea. Initially, the noise exposure may cause a temporary threshold
shift-that is, a decrease in hearing sensitivity that typically returns to its
former level within a few minutes to a few hours. Repeated exposures lead to a
permanent threshold shift, which is an irreversible sensorineural
hearing loss.
Approximately
30 million workers are exposed to hazardous noise on the job and an additional
nine million are at risk for hearing loss from other agents such as solvents
and metals.
Noise-induced
hearing loss is one of the most common occupational diseases and the second
most self-reported occupational illness or injury. Industry specific studies
reveal:
While
any worker can be at risk for noise-induced hearing loss in the workplace, workers
in many industries have higher exposures to dangerous levels of noise.
Industries with high numbers of exposed workers include: agriculture; mining;
construction; manufacturing and utilities; transportation; and military.
Removing
hazardous noise from the workplace through engineering controls (e.g.
installing a muffler or building an acoustic barrier) is the most effective way
to prevent noise-induced hearing loss. Hearing protectors such as ear plugs and
ear muffs should be used when it is not feasible to otherwise reduce noise to a
safe level. NIOSH recommends hearing loss prevention programs for all
workplaces with hazardous levels of noise. These programs should include noise
assessments, engineering controls, audiometric monitoring of workers’ hearing, appropriate use of hearing protectors, worker education,
record keeping, and program evaluation.
Type of Sounds that Cause NIHL:
NIHL can be caused by a one-time exposure to loud sound as well as by repeated
exposure to sounds at various loudness levels over an extended period of time.
The loudness of sound is measured in units called decibels. For example, usual
conversation is approximately 60 decibels, the humming of a refrigerator is 40
decibels and city traffic noise can be 80 decibels. Examples of sources of loud
noises that cause NIHL are motorcycles, firecrackers and small arms fire, all
emitting sounds from 120 decibels to 140 decibels. Sounds of less than 75
decibels, even after long exposure, are unlikely to cause hearing loss.
Exposure
to harmful sounds causes damage to the sensitive hair cells of the inner ear
and to the nerve of hearing. These structures can be injured by noise in two
different ways: from an intense brief impulse, such as an explosion,
or from continuous exposure to noise, such as that in a woodworking shop.
Effects of NIHL:
The effect from impulse sound can be instantaneous and can result in an
immediate hearing loss that may be permanent. The structures of the inner ear
may be severely damaged. This kind of hearing loss may be accompanied by
tinnitus, an experience of sound like ringing, buzzing or roaring in the ears
or head, which may subside over time. Hearing loss and tinnitus may be
experienced in one or both ears, and tinnitus may continue constantly or
intermittently throughout a lifetime.
The
damage that occurs slowly over years of continuous exposure to loud noise is
accompanied by various changes in the structure of the hair cells. It also
results in hearing loss and tinnitus. Exposure to impulse and continuous noise
may cause only a temporary hearing loss. If the hearing recovers, the temporary
hearing loss is called a temporary threshold shift. The temporary threshold
shift largely disappears within 16 hours after exposure to loud noise.
Both
forms of NIHL can be prevented by the regular use of hearing protectors such as
ear plugs or ear muffs.
Symptoms of NIHL:
The symptoms of NIHL that occur over a period of continuous exposure increase
gradually. Sounds may become distorted or muffled, and it may be difficult for
the person to understand speech. The individual may not be aware of the loss,
but it can be detected with a hearing test.
Hazard levels and risks:
(1)
Exposure to excessive noise for an extended period of time can damage the inner
ear in such a way that the ability to hear high frequency sound is diminished
or lost.
(2)
Excessive noise can cause quickened pulse, increased blood pressure and
constriction of blood vessels.
Factors that affect the risk of hearing loss:
Intensity of the noise (Sound pressure level)
Type of noise (Wide band, narrow band, impulse)
Duration of daily exposure
Total duration of exposure
Age of the individual
Coexisting hearing disease
Distance from the noise source
Noise
exposure and noise-induced hearing loss pose an increased health risk to the
workers. Noise exposure can lead to hearing loss and balance dysfunction. A
study found that occupational noise exposure made iron workers prematurely deaf
and impaired their balance. Serious and deadly falls on construction sites may
be related to noise-induced balance dysfunction and impaired equilibrium.
Elevated noise levels pose an additional threat of injury or death to workers
by reducing communication among them and between supervisors and workers and by
reducing the effectiveness of audible warning devices.
There
are a variety of control techniques documented in the literature to reduce the
overall worker exposure to noise. Such controls reduce the amount of sound
energy released by the noise source, or divert the flow of sound energy away
from the receiver, or protect the receiver from the sound energy reaching
him/her. For example, types of noise controls include proper maintenance of
equipment, revised operating procedures, equipment replacements, acoustical
shields and barriers, equipment redesign, enclosures, administrative controls,
and personal protective equipment.
Standards and Regulations:
The
primary sources of standards and regulations relating to noise hazards are OSHA
and The American National Standards Institute (ANSI). OSHA regulations require
the implementation of hearing conservation programs under certain conditions. OSHA's regulations should be considered as minimum
standards. ANSI's standard provides a way to determine the effectiveness of
hearing conservation programs such as those required by OSHA.
ANSI Standard (S12.13-1991):
In
1991 the American National Standards Institute (ANSI) published ANSI standard
S12.13-1991, entitled "Evaluation of Hearing Conservation Programs". This
standard is designed to help safety and health professionals determine if
hearing conservation programs work the way they are intended.
Federal
regulations require that employees be protected from excessive noise in the
workplace. However, they provide no methodology for determining the
effectiveness of hearing conservation programs. The primary reason for the
development of ANSI standard was because hearing conservation programs were not
really protecting employess but were actually only
recording their steadily declining hearing ability.
The
working group that developed the standard used audiometric database analysis
(ADBA) to identify procedures for measuring variability in hearing threshold
levels. The two procedures that were identified were as follows:
Percent worse sequential.
This procedure identifies the percentage of subjects who show a deterioration
of 15 dBA or more in their ability to hear at least
one test frequency (500 through 6000 Hz) in either ear between two sequential
audiograms.
Percent better or worse
sequential. This procedure identifies the percentage of subjects who
show either a deterioration or an improvement of 15 dBA or more in threshold for at least one test frequency
(500 through 6000 Hz) in either ear between two sequential audiograms.
Results of tests are compared in sequence. For
example, the results of year 4 are compared with those of year 3. The results
of year 3 are compared with those of year 2 and so on. In this way, a current
audiogram is compared against an earlier audiogram. The results of the earlier
test are use da s a baseline
for comparison.
Test results from several employees in a given work
unit are examined individually and compared with past results sequentially. If
enough employees show hearing loss, it might be concluded that the work unit's
conservation program is ineffective.
OSHA regulation: (29 CFR 1910.95):
OSHA
requires employers to implement hearing conservation programs, where employees
are exposed to an eight -hour time weighted average of 85 dBA
noise and above.
(1)
Monitoring noise levels: Should be on a regular basis, whenever a
new process, equipment or machinery is added.
(2)
Medical surveillance: New employees who are exposed to high noise
levels are to be tested upon being hired and existing employees are to be
tested at least once a year.
(3)
Noise controls: If the noise level is below 100 dBA administrative controls are sufficient. For noise
levels above 100 dBA engineering controls are
necessary.
(4)
Personal protection: Ear plugs, ear muffs must be used in
addition to, rather than instead of administrative and engineering controls.
|
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|
|
|
Ear Muffs |
Cap Mounted Ear Muffs |
Ear Muffs with Built-in Radio -Communication Circuitry |
Figure 5. Various Types of Ear Muffs
(Courtesy of ELVEX
Corporation)
|
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|
|
Ear Plugs |
Ear Canal Cap |
Figure 6. Ear Plugs and Canal-Cap Style
Hearing Protection Devices (Courtesy of ELVEX Corporation)
(5)
Education and training: Should include:
How the ear works
How to interpret the results of audiometric tests
How to select PPEs
How to properly use PPEs
OSHA's Permissible Noise Exposure Levels:
|
Duration (hrs) |
Sound level (dBA) |
|
8 |
90 |
|
6 |
92 |
|
4 |
95 |
|
3 |
97 |
|
2 |
100 |
|
1.5 |
102 |
|
1 |
105 |
|
0.5 |
110 |
|
0.25 or less |
115 |
|
Impulse or impact noise |
140 peak level |
Time-weighted average noise (TWAN):
For
TWAN = 1.00 or TWAN <1.00 no hearing protection is necessary.
C1,
C2,...Cn
= Total time of actual exposure at a specified noise level on an 8-hour work
day
T1,
T2,...Tn
= Total time of exposure permitted at the specified noise level by OSHA.
Example:
A worker is exposed to the following noise level:
|
Noise level (dBA) |
Duration (Hr) |
|
90 |
4 |
|
95 |
1 |
|
100 |
0.25 |
|
110 |
0.25 |
The
rest of the time the noise level is below 85 dBA. Is
the OSHA criteria exceeded ?
|
OSHA's Permissible Noise Exposure Limit |
|
Actual Exposure Level |
|
Duration (hrs) |
Sound level (dBA) |
Duration (Hr) |
|
8 |
90 |
4 |
|
4 |
95 |
1 |
|
2 |
100 |
0.25 |
|
0.5 |
110 |
0.25 |
Time-weighted
average noise (TWAN) is given by:
TWAN
= 4/8 + 1/4 + 0.25/2 + 0.25/0.5 = 0.50 + 0.250 + 0.125+ 0.50 = 1.375
TWAN
= 1.375 > 1.00. Time weighted average noise exceeds the OSHA criteria and
hearing protection is required.
Worker's
Compensation and Noise Hazards:
Hearing
loss claims are being covered by state worker's compensation laws. Some states
have actually written hearing loss into their worker's compensation law. Others
are covering claims whether hearing loss is in the law or not. While there is
no standardized procedure for negotiating levels of compensation, there has
been a steady, upward trend in cost-per-case during the past decade. For
instance, average maximum award given by the state worker's compensation
programs for total loss of hearing in both ears is about $ 40,000 and the same
type of hearing loss among federally administered programs exceeds $180,000.
It
has been estimated that 1.7 million workers in the
Measurement of the Noise level:
Identifying
and assessing hazardous noise conditions in the workplace involve the
following:
Conducting periodic noise surveys
Conducting periodic audiometric tests
Record keeping
Follow-up action
Noise Surveys: Conducting noise surveys involves measuring noise levels at different
locations in the workplace. The devices that are most widely used to measure
noise levels are sound level meters and dosimeters.
A sound level meter produces an immediate reading that represents
the noise level at a specific instant in time. A dosimeter provides
a time weighted average over a period of time such as one complete work shift.
The dosimeter is the most widely used device because it measures total
exposure, which is what OSHA and ANSI standards specify. Using a dosimeter in
various work areas and attaching a personal dosimeter to one or more employees
is the recommended approach to ensure dependable, accurate readings.
|
|
|
|
|
Digital Sound Level Meter |
Dosimeter |
Analog Sound Level Meter |
Figure 7. Various types of
noise measuring devices. (Courtesy of GENEQ Inc.)
Dosimetry: Many workers receive noise
exposures that vary almost constantly during a work day. In 1981 OSHA required
hearing conservation programs for workers exposed to TWAN levels greater than
85 dBA. Noise dose D measures varying exposures over
a period of time and is equivalent to an exposure of 90 dBA
for an 8 hour period. Noise dose (D) in % is given by:
Where,
C=
Total length of the workday in hours
T
= Reference duration in hours for sound level L
L
= Sound level in dBA
The
reference duration,T, is
computed as:
Example:
A worker is exposed to a 95 dBA constant noise source
during an 8 hour shift. What is the noise dose ?
And
the noise dose is:
Audiometric Testing: Audiometric testing measures the hearing threshold of
employees. Tests conducted according to ANSI S12.13-1991 can detect changes in
the hearing threshold of the employee. A negative change represents hearing
loss within a given frequency range.
The
initial audiogram establishes a baseline hearing threshold. After that,
audiometric tetsing should occur at least annually.
Testing should not be done on an employee who has a cold, an ear infection, or
who has been exposed to noise levels exceeding 80 dBA
within 14 to 16 hours prior to a test. Such conditions can produce invalid
results.
When
even small changes in an employee's hearing threshold are identified, more
frequent test should be scheduled and conducted as specified by ANSI standard.
For those employees found to have standard threshold shift- aloss
of 10dBA or more averaged at 2000, 3000 and 4000 Hz in either ear-the employer
is required to fill out an OSHA 200 Formin which the
loss of hearing is recorded as a work-related illness.
Recordkeeping: Noise exposure measurement records must be kept for
2 years. Records of audiometric test results must be maintained for the
duration of employment of the affected employee. Audiometric test records must
include the name and job classification of the employee, the date, the
examiner's name, the date of the last acoustic or exhaustive calibration,
measurements of the background sound pressure levels in audiometric test rooms,
and the employee's most recent noise exposure measurement. Figure 8 shows an
example for an audiometric test form that can be used to record test results
for individual employees.
Figure 8. Sample Audiometric Test Result
Form.
Follow-Up:
One of the most significant deficiencies associated with audiometric monitoring
in occupational settings is failure to take appropriate action when the
earliest stage of noise-induced hearing loss is observable. Hearing loss can
occur without producing any evidence of physiological damage. Therefore, it is
important to follow up on even the slightest evidence of change in an
employee's hearing threshold. Follow-up can be done in many different ways:
Administering a retest to verify
the hearing loss.
Changing or improving the type of PPE.
Conducting a new noise survey in
the employee's work area to determine if engineering controls are sufficient.
Testing other employees to
determine if the hearing loss is isolated to the one employee in question or if
other employees have also been affected.
Exposure to Noise Generated by Different Sources Simultaneously:
When
employees are exposed to noise from different sources at the same time, the
combined sound level from these sources must be taken into account for
compliance and control measures. The following equation is used to calculate
the combined sound level from two random sources:
Lc = Combined level in decibels
L1,
L2 = Individual sound levels in decibels
If
the sound level from more than two random sources is to be calculated, use the
following procedure:
(1)
Add the two lowest decibel levels first,
(2)
Add the result of step 1 to the next higher decibel
level,
(3)
Continue until all decibel levels have been added.
Example:
Five machines are operating in a machine shop, and each one is generating a
sound level as summarized below:
|
Machine |
Noise Level (dBA) |
|
Machine 1 |
79 dBA |
|
Machine 2 |
85 dBA |
|
Machine 3 |
87 dBA |
|
Machine 4 |
95 dBA |
|
Machine 5 |
93 dBA |
Compute the combined noise level in
DBA.
Step 1. Add the two lowest decibel levels first. Machine 1 and Machine 2 have the
lowest noise levels. L1 = 79 dBA and L2
= 85 dBA
Combined
effect from Machine 1 and Machine 2 = Lc .
and the combined effect of Machine 1 and Machine 2 will be:
Step 2. Add the result of step 1 to the next higher decibel level. Machine 3 is the next higher one
with L2 = 87 dBA. Now consider L1 =
86 dBA from the previous calculation which indicates
the combined effect of Machines 1 and 2.
and the combined effect of machines 1,
2 and 3 will be:
Step 3.
Continue until all
decibel levels have been added. The next higher decibel level is 93 dBA
which is created by Machine 5. L2 = 93 and L1 = 90 dBA
and the combined effect of machines 1,
2 ,3 and 4 will be:
Step 4. The next higher decibel level is 95 dBA
which is created by Machine 4. L2 = 95 and L1 = 95 dBA.
and the combined effect of machines 1,
2 ,3,4 and 5 will be:
Therefore,
the combined effect from all five machines operating simultaneously is
equivalent to a sound level of 98 dBA.
Instruments:
Sound level meter: Measures from 20 to 20,000 Hz. Sound is measured by using a microphone.
Can not be used for impulses.
Impulse meter: Measures peak of transient sounds. Responds very
quickly.
Frequency analyzer: Measures the distribution of sound across one or more bandwidths.
Dosimeters: Pocket
size portable instrument to record noise levels exposed during the workday.
Engineering Controls:
There
are many controls for noise. Engineering controls can be grouped into four
classes:
Avoid noise sources before they are introduced into a
work or other environment.
If noise source exists, replace equipment, processes
or materials with quieter ones.
If noise sources cannot be replaced, modify them.
Modify sound distributed in the environment.
Design of Rooms to Absorb Sound:
A
room constant R is a measure of the ability of a room to absorb sound. A high
room constant will have a high level of sound absorption. A room constant can
be computed as:
where,
a m = Mean sound
absorption coefficient for all room surfaces (dimensionless)
St
= Total area of room boundary surfaces (square feet)
where, S1 ... S2 ...... Sn refer to individual
surface areas and a 1 ... a 2 ......a n refer to absorption coefficient of
each material.
Noise Reduction:
The
noise reduction is computed as:
where NR= Noise reduction
A1
= Total absorption units (sabins) in a room before
treatment (A1=S1a 1 + S2a 2 + ... Sna n)
A2=
Total absorption units (sabins) in a room after the
treatment
The
absorption properties of room finish materials vary with frequencies.
Manufactures of sound absorbing materials usually have data on absorption
coefficients that are listed by bandwidth frequency. The sound absorption for a
clothed person in a room varies with frequency and is about 3-5 sabins.
Example:
A room measures 50 ft wide, 70 ft long and 12 ft high. It has a 90 dBA sound level from some source at a frequency of 1000 Hz.
The surfaces in the room and their absorption coefficients are given below:
|
Surface |
Absorption Coefficient at 1000 Hz |
|
Ceiling |
0.02 |
|
Floor |
0.02 |
|
Walls |
0.01 |
|
Covered Pipe (180 ft2) |
0.50 |
|
Machinery (200 ft2) |
0.02 |
|
8 people |
4 sabins /person |
To
reduce the sound levels, the room is modified by covering the ceiling with acoustical
tile. The tile has an absorption coefficient of 0.80 at 1000 Hz.
(a)
What noise reduction NR, in decibels, is achieved?
(b)
What is the resulting sound level in the room after modification?
A1=(0.02)(3500)+(0.02)(3500)+[(2)(50x12)+(2)(70x12)]x(0.01)+(0.50)(180)+(0.02)(200)+(4)(8)=294.8
A2=(0.80)(3500)+(0.02)(3500)+[(2)(50x12)+(2)(70x12)]x(0.01)+(0.50)(180)+(0.02)(200)+(4)(8)=3024.8
NR
= 10 log (A2/A1)= 10 log(3024.8/294.8) = 10
The
noise reduction NR = 10 dBA
Resulting
noise in the room = 90-10 = 80 dBA
Vibration
Hazards:
Sound
and vibration are very similar. Sound typically relates to a sensation that is
perceived by the inner ear as hearing. Vibration, on the other hand, is
inaudible and is perceived through the sense of touch. Vibration hazards are
closely associated with noise hazards because tools that produce vibration
typically also produce excessive levels of noise.
Vibration
hazards depend on the source of vibration. Workers who operate heavy equipment
often experience vibration over the whole body. This can lead to problems
ranging from motion sickness to spinal injury.
Environmental
conditions and worker habits can exacerbate the problems associated with vibration.
For example, working with vibrating tools in a cold environment is more
dangerous than working with the same tools in a warm environment. Gripping a
vibrating tool tightly will lead to problems sooner than using a loose grip.
The
most common vibration related problem is known as Hand-arm vibration
syndrome (HAV) which is an irreversible damage to the nerves and blood
vessels. Exposure to cold, excessive amount of noise, smoking can increase the
potential for HAV.
Vibration injury prevention:
Purchase low vibration tools.
Limit employee exposure.
Change employee work habits:
Wear thick gloves that absorb vibration.
Take periodic breaks.
Keep warm (Cold accelerates the HAV).
Use vibration absorbent mats and seat covers.
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Updated : January 9, 2007 By: Serdar Z. Elgun |