Noise and Vibration

1
(No Transcript)
2
(No Transcript)
3
Noise and Vibration

• Noise in the modern workplace poses two safety-
  and health-related problems.
• Noise can distract workers and disrupt
  concentration, which can lead to accidents.
• Exposure to noise that exceeds prescribed levels
  can result in permanent hearing loss.

4
HEARING LOSS PREVENTION TERMS

• Terms common to hearing loss prevention
• Attenuation Real-world baseline audiogram - the
  estimated sound protection provided by hearing
  protective devices as worn in real-world
  environments.
• Baseline audiogram - a valid audiogram against
  which subsequent audiograms are compared to
  determine if hearing thresholds have changed.
• Continuous noise - noise of a constant level
  measured over at least one second using the
  slow setting on a sound level meter.

5
HEARING LOSS PREVENTION TERMS

• Terms common to hearing loss prevention

• Decibel (dB) - unit used to express the intensity
  of sound, named after Alexander Graham Bell.
• A logarithmic scale in which 0 Db approximates
  the thresholdof hearing in the midfrequencies
  for young adults.
• The threshold of discomfort is between 85 and 95
  dB.
• The threshold of pain is between120 and 140 dB.

• Dosimeter - the instrument that measures sound
  levels over a specified interval, stores the
  measures, and calculates the sound as a function
  of sound level and sound duration.

6
HEARING LOSS PREVENTION TERMS

• Terms common to hearing loss prevention

• Exchange rate - relationship between intensity
  and dose.
• OSHA uses a 5-dB exchange rateif the intensity
  of an exposure increases by 5 dB, the dose
  doubles, also referred to as the doubling rate.
• The U.S. Navy uses a 4-dB exchange rate the U.S.
  Army and Air Force use a 3-dB exchange rate.

• Hazardous Noise - any sound for which any
  combination of frequency, intensity, or duration
  is capable of causing permanent hearing loss in a
  specified population
• Conductive and sensorineural loss - hearing loss
  is often characterized by the area of the
  auditory system responsible for the loss.

7
HEARING LOSS PREVENTION TERMS

• Terms common to hearing loss prevention

• Hearing threshold level (HTL) - hearing level,
  above a reference value, at which a specified
  sound or tone is heard by an ear in a specified
  fraction of the trials.
• Hearing threshold levels have been established so
  that dBHTL reflects the best hearing of a group
  of persons. Hertz (Hz).

• Hertz (Hz) - unit measurement for audio
  frequencies.
• The frequency range for human hearing lies
  between 20 Hzand approximately 20,000 Hz.
• Impulsive noise - impact or impulse noise
  typified by a sound that rapidly rises to a sharp
  peak quickly fades.
• The sound may or may not have a ringing quality
  (such as striking a hammer on a metal plate, and
  may be repetitive, or may be a single eventlike
  a sonic boom.

8
HEARING LOSS PREVENTION TERMS

• Terms common to hearing loss prevention

• Noise - any unwanted sound.

• Noise dose - the noise exposure expressed as a
  percentage of the allowable daily exposure.
• OSHA considers a 100 dose equals an eight-hour
  exposureto a continuous90-dBA noise.
• Noise-induced hearing loss - sensorineural
  hearing loss attributed to noise, for which no
  other etiology can be determined.
• Standard threshold shift (STS) - OSHA term to
  describe change in hearing threshold relative to
  the baseline audiogram of an average of 10 dB or
  more at 2,000, 3,000, and 4,000 Hz in either ear.

9
HEARING LOSS PREVENTION TERMS

• Terms common to hearing loss prevention

• Time-weighted average (TWA) - a value, expressed
  in dBA, computed so that the resulting average is
  equivalent to an exposure resulting from a
  constant noise level over an eight-hour period.

10
CHARACTERISTICS OF SOUND

• Sound is any pressure change that can be detected
  by the eartypically a change in air pressure.
• It can also be a change in water pressure or any
  other pressure-sensitive medium.
• What we think of as sound, the eardrum senses as
  fluctuations in atmospheric pressure.
• The eardrum responds to these fluctuations by
  vibrating.
• The vibrations are carried to the brain in the
  form of neural sensations and interpreted as
  sound.
• Sound can occur in any medium that has both mass
  and elasticity (air, water, etc.).

11
CHARACTERISTICS OF SOUND
12
CHARACTERISTICS OF SOUND
13
CHARACTERISTICS OF SOUND
14
CHARACTERISTICS OF SOUND
15
CHARACTERISTICS OF SOUND

• The three broad types of industrial noise are
  described as follows
• Wide band noise - noise that is distributed over
  a wide range of frequencies.
• Most noise from manufacturing machines is wide
  band noise.
• Narrow band noise - is confined to a narrow range
  of frequencies, such as that produced by power
  tools.
• Impulse noise - transient pulses that can occur
  repetitively or nonrepetitively, such as noise
  producedby a jackhammer.

16
HAZARD LEVELS AND RISKS

• Exposure to excessive noise levels for an
  extended period can damage the inner ear.
• Ability to hear high-frequency sound is
  diminished or lost.
• Additional exposure can increase damage until
  even lower frequency sounds cannot be heard.

17
HAZARD LEVELS AND RISKS

• Factors hearing loss associated with exposure to
  excessive noise
• Intensity of the noise (sound pressure level).
• Type of noise (wide band, narrow band, or
  impulse).
• Duration of daily exposure.
• Total duration of exposure (number of years).
• Age of the individual.
• Coexisting hearing disease.
• Nature of environment in which exposure occurs.
• Distance of the individual from the source of the
  noise.
• Position of the ears relative to the sound waves.

18
HAZARD LEVELS AND RISKS
19
STANDARDS AND REGULATIONS

• OSHA regulations require implementation of
  hearing conservation programs under certain
  conditions.
• OSHA regulations should be considered minimum
  standards.
• ANSI standards provide a way to determine the
  effectiveness of hearing conservation programs
  such as those required by OSHA.
• NIOSH bases most of its materials on OSHA
  regulations, although it makes recommendations
  that exceed OSHA regulations in some cases.

20
ANSI Standard

• ANSI developed the standard used audiometric
  database analysis (ADBA) to identify procedures
  for measuring variability in hearing threshold
  levels
• Percent worse sequential - identifies the
  percentage of subjects who show a deterioration
  of 15 dBA or more in their ability to hear at
  least one test frequency in eitherear between
  two sequential audiograms.
• Percent better or worse sequential - identifies
  subjects who show a deterioration or an
  improvement of 15 dBA or more in thresholds for
  at least one test frequency in either ear between
  two sequential audiograms.

21
OSHA Regulations

• OSHA 29 CFR 1910.95 requirements for hearing
  conservation programs are as follows
• Hearing hazards monitoring.
• Engineering and administrative controls.
• Audiometric evaluation.
• Personal hearing-protection devices.
• Education and motivation.
• Record keeping Program evaluation.

22
Hazards Monitoring

• The most common measurements are area surveys,
  dosimetry, and engineering surveys.
• Area survey results are often plotted in the form
  of anoise map, showing noise level measurements
  for the different areas of the workplace.
• Dosimetry involves the use of body-worn
  instruments (dosimeters) to monitor exposure over
  the work shift.
• Engineering surveys typically employ more
  sophisticated acoustical equipment inaddition to
  sound-level meters.

23
Engineering and Administrative Controls

• Engineering and administrative controls represent
  the first two echelons in the hierarchy of
  controls
• Remove the hazard and remove the worker.
• These controls should reduce hazardous exposure
  to the point where the risk to hearing is
  eliminated,or at least more manageable.
• Engineering controls are technologically feasible
  for most noise sources, but their economic
  feasibility must be determined on a case-by-case
  basis.

24
Engineering and Administrative Controls

• Assessing the applicability of engineering
  controls is a sophisticated process.
• The noise problem must be thoroughly defined, and
  an assessment of the effect of the controls on
  overall noise levels should be made.
• Once identified and analyzed, the choice of
  controls can be consideredinfluenced, to some
  extent, by the cost of purchasing, operating,
  servicing, and maintaining the control.
• An acoustical consultant may be hired to assist
  in the design, implementation, installation, and
  evaluation.

25
Engineering and Administrative Controls

• Administrative controls are changes in the work
  schedules or operations that reduce noise
  exposure.
• Generally of limited use in industry because
  employee contracts seldom permit shifting from
  one job to another.
• The practice of rotating employees between quiet
  and noisy jobs may reduce the risk of substantial
  hearing loss in a few workers, but actually
  increase the risk of small hearing losses in many
  workers.
• A more practical administrative control is to
  provide for quiet areas where employees can gain
  relieffrom workplace noise.

26
Audiometric Evaluation

• Audiometric evaluation is the only way to
  determine whether hearing loss is being
  prevented.
• Occupational hearing loss occurs gradually is
  not accompanied by pain, so an affected employee
  may not notice the change until a large threshold
  shift accumulates.
• OSHA uses the term standard threshold shift to
  describe an average change in hearing from the
  baseline levels of 10 dB or more for the
  frequencies of 2,000, 3,000, and 4,000 Hz.
• NIOSH uses the term significant threshold shift
  to describe a change of 15 dB or more at any
  frequency of 500 - 6,000 Hz from baseline levels,
  present on an immediate retest in the same ear
  and at the same frequency.

27
Audiometric Evaluation

• Audiograms should be performed on the following
  occasions
• Preemployment/prior to initial assignment in a
  hearing hazardous work area.
• Annually while the employee is assigned to a
  noisy job.
• At time of reassignment out of a hearing
  hazardous job.,
• At the termination of employment.
• Employees who are not exposed should be given
  periodic audiograms as part of the organizations
  health care program.

28
Personal Hearing Protection Devices

• A personal hearing protection device (or hearing
  protector) is anything that can be worn to
  reduce the level of sound entering the ear.
• Earmuffs, ear canal caps earplugs are the 3
  main types.

• Regardless of the kind of ear protection device
  used, it is important to remember the four Cs
• Comfort, convenience.
• Communication (the device should not interfere
  with the workers ability to communicate).
• Caring (workers must care enough about protecting
  their hearing to wear the devices).

29
Personal Hearing Protection Devices

• There are several different types of earmuffs
• Passive earmuffs consist of ear cups lined with
  foam and block noise using nothing but the
  foam-lined cups.
• They tend to block out not just unwanted noise,
  but also certain advantageous sounds, such as
  voices trying to warn of danger.
• Uniform attenuation earmuffs block noise, and
  also attenuate the noise more uniformly within
  several key octave bands (250 Hz to 4 KHz).
• This allows employees to hear certain important
  sounds such as spoken instructions or warnings.
• Electronic earmuffs use electronic technology to
  both block and modulate sound.
• Some can receive AM/FM radio signals or have a
  wireless connection to a CD or MP3 player.

30
Education and Motivation

• To obtain sincere, energetic management support
  and active employee participation, it is
  necessaryto educate and motivate both groups.
• Employees managers who appreciate the sense of
  hearing and understand the reasons for, and the
  mechanics of, the hearing loss prevention program
  will be more likely to participate.
• Rather than viewing the program as an imposition.

31
Record Keeping

• Audiometric comparisons, reports of hearing
  protector use, and analysis of hazardous exposure
  measurements all involve the keeping of records.
• Records are often kept poorly because there is no
  organized system, and those responsible for
  maintaining the records do not understand their
  value.
• Many companies have found that their
  record-keeping system is inadequate only when
  they discover that they need accurate
  information.
• Sometimes during processing of compensation
  claims.
• Problems can be avoided by implementing an
  effective record-keeping system.

32
Program Evaluation

• A thorough evaluation of the effectiveness of all
  the programs components is necessary to
  determine the extent to which the hearing loss
  prevention program is really working.
• Assess the completeness and quality of the
  programs components and evaluate the audiometric
  data

33
WORKERS COMPENSATION NOISE HAZARDS

• Some states have written hearing loss into their
  workers compensation law, and others cover
  claims whether hearing loss is in the law or not.
  
• Medical professionals have established a
  procedure for determining if there is a causal
  relationship between workplace noise and hearing
  loss.
• Because about 15 of all working people are
  exposed to noise levels exceeding 90 dBA, hearing
  loss may be as significant in workers
  compensation costs in the future as back
  injuries, carpal tunnel syndrome, and stress are
  now significant.

34
IDENTIFYING/ASSESSING HAZARDOUS NOISE

• Identifying and assessing hazardous noise
  conditions in the workplace involve.
• Conducting periodic noise surveys.
• Conducting periodic audiometric tests.
• Record keeping.
• Follow-up action.

35
NOISE CONTROL STRATEGIES
36
NOISE CONTROL STRATEGIES

• The most desirable noise controls are those that
  reduce noise at the source.
• The second priority is to reduce noise along its
  path.
• The last resort is noise reduction at the
  receiver using personal protective devices.
• The latter approach should never be substituted
  for the two former approaches.

37
VIBRATION HAZARDS

• Vibration hazards are closely associated with
  noise hazards because tools that produce
  vibrationtypically also produce excessive levels
  of noise.
• Vibration-related problems are serious
  widespread.
• Up to 8 million workers are exposed to some type
  of vibration hazard, and of these, it is
  estimated thatmore than half will show some
  signs of injury.
• Types of injuries associated with vibration
  depend on its source.

38
VIBRATION HAZARDS

• The most common vibration-related problem is
  known as hand-arm vibration syndrome(HAV).
• HAV is a form of Reynauds Syndrome, striking
  workers who use vibrating power tools daily as
  part of their jobs.

• Environmental conditions and worker habits can
  exacerbate the problems associated with
  vibration.
• Working with vibrating tools in a cold
  environment is more dangerous than the same work
  in a warm environment.
• Gripping a vibrating tool tightly will lead to
  problemssooner than using a loose grip.
• Smoking and excessive noise also increase
  potentialfor HAV and other vibration-related
  injuries.

39
VIBRATION HAZARDS

• Prevention is especially important with HAV
  because the disease is thought to be
  irreversible.
• Treatments developed to date only reduce the
  symptoms.

• Prevention strategies that can be used in any
  company regardless of its size
• Purchase low-vibration tools.
• Limit employee exposure.
• Change employee work habits.

40
OTHER EFFECTS OF NOISE HAZARDS

• Noise can cause communication problems,
  isolation, and productivity problems.
• Noise can also be detrimental to productivity by
  interfering with an employees ability to think,
  reason, and solve problems.

41
CORPORATE POLICY

• Organizations with the most successful hearing
  loss prevention programs address the following
  areas
• The organizational environment should promote a
  safety culture where employees are empowered to
  protect their own health and that of coworkers.
• Policies should be based on effective practices
  rather than on minimum compliance with government
  regulations.
• The hearing prevention program must be a
  functional part of the overall company safety
  health program.
• Not a stand-alone, separate-budget operation.
• A key individual (or program implementor) should
  have ultimate responsibility for the program.
• Employee administrative compliance with the
  program.

42
EVALUATING PREVENTION PROGRAMS

• Hearing loss prevention programs should be
  evaluated periodically to ensure their
  effectiveness.
• Training and education.
• Supervisor involvement.
• Noise measurement.
• Engineering and administrative controls.
• Monitoring and record keeping,
• Referrals.
• Hearing protection devices.
• Administration.