Transcript Document

Noise at Work
Mark Mallen
Group Health and Safety Manager
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Introduction
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Noise at work and how it can affect you
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Objectives
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What is noise?
What is sound?
How do we hear?
Measuring noise?
Hearing Loss
The Law
– Employer duties
– Employee duties
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PPE
– Where, what and when
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Content
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What is noise?
Sound
How do we hear?
The measurement of noise
Hearing Loss
The Law
- Noise at Work Regulations 1989
- The Control of Noise at Work Regulations 2005
Information, instruction, and training
- What we need to tell you
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What is Noise?
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Noise
– Noise is unwanted sound.
– One person’s music could be another’s
noise!
– The ear does not differentiate between
noise and sound - The brain does that!
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What is Noise?
Effects
 Short term
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– Annoy
– Distract
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Long term
– Deafness
– Tinnitus
– Noise Induced Hearing Loss (NIHL)
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Sound
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The sensation produced via the ear,
– results from fluctuations in air pressure
– Caused by vibrating air molecules
– The source of the sound vibrates
– Creates a sound pressure wave
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Sound
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Like ripples on a pond – sound
pressure wave
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Sound
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A Sound Wave
– created by a vibrating object:
The vocal chords
 A guitar string
 A machine
 Traffic
 The diaphragm of a radio speaker
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Sound
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Air moves back and forth
– The frequency of a wave
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If a particle of air undergoes 1000
vibrations in 2 seconds
– Then the frequency of the wave is 500
vibrations per second
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The unit of frequency is the hertz
(abbreviated Hz), where:
– 1 Hertz = 1 vibration/second
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Sound
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The human ear detects
– Ranges between approximately 20 Hz to
20 000 Hz
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Any sound less than 20 Hz
– Infrasound
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Any sound above 20 000 Hz
– Ultrasound
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How do we hear Sound?
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The Ear
– The outer ear
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Collects and channels sound to the middle ear.
– The middle ear
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Transforms the energy of a sound wave into internal
vibrations via a bone structure.
– The inner ear
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The inner ear transforms these vibrations into nerve
impulses, which can be transmitted to the brain.
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The Ear
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The Outer Ear
Consists of an earflap and an ear canal
 The earflap protects the middle ear
and eardrum
 It also channels sound waves to the
eardrum
 Sound is still a sound pressure wave
 At the eardrum, the wave converts into
vibrations
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The Middle Ear
An eardrum
– A membrane, which connects to the
hammer
 Three tiny, interconnected bones
– Hammer, anvil & stirrup
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– Act as levers to amplify the sound wave
– The stirrup concentrates sound wave by 15
– This enhances our ability of hear faint sounds
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The Middle Ear
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The Eustachian tube
– Connects the middle ear via a tube to the
mouth
– Allows for the equalization of pressure within
the air-filled cavities
– When clogged i.e. During a cold, the ear
cavity is unable to equalise pressure; often
leads to earaches and other pains
The stirrup transmits vibrations to the inner
ear, via the oval window
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The Inner Ear
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Full of a water like fluid
The stirrup creates a wave within this fluid
The inner ear consists of
– A cochlea
– The semicircular canals
– And the auditory nerve
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The fluid and nerve cells of the semicircular
canals provide no roll in the task of hearing
– They serve as accelerometers for detecting
accelerated movements
– Assist in the task of maintaining balance
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The Ear
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The Cochlea
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Snail-shaped organ
– Lined with over 20 000 hair-like nerve cells
– These nerve cells differ in length by minuscule amounts
– They have different degrees of resiliency to the fluid
– The hair-like nerve cells are set in motion by the wave
– Each hair cell has a natural sensitivity to a particular
frequency of vibration
– When the wave matches the natural frequency of the
nerve cell, an electrical impulse is released
– Which passes along the auditory nerve to the brain
– The brain then interprets the qualities of the sound upon
reception of these electric nerve impulses
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The Measurement Of Noise
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Decibels
– Humans have very sensitive ears
– The lowest sound corresponds to the displacement of air
particles by one-billionth of a centimetre
– Known as the ‘threshold of hearing’
– The most intense sound
 Which the ear can detect without suffering any damage
– More than one billion times more intense
– Known as the ‘threshold of pain’
Since the range of intensities is so large, a scale based on
multiples of 10 is used
– Known as a logarithmic scale
– The scale for measuring intensity is the decibel scale
Decibels are written as: db
At the ear db (A)
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The Measurement of Noise
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The threshold of hearing is assigned a sound level
of 0 decibels, abbreviated 0 dB.
A sound, which is 10 times more intense, is
assigned a sound level of 10 dB.
A sound, which is 10 x 10 or 100 times more
intense, assigned a sound level of 20 db.
A sound, which is 10 x 10 x 10 or 1000 times more
intense, is assigned a sound level of 30 db.
A sound, which is 10 x 10 x 10 x 10 or 10000 times
more intense, is assigned a sound level of 40 db.
This scale is based on powers or multiples of 10
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Typical Noise Levels
Source
Threshold of Hearing - TOH
Rustling Leaves
Whisper
Normal Conversation
Busy Street Traffic
Vacuum Cleaner
Large Orchestra
Walkman at Maximum Level
Front Rows of Rock Concert
Threshold of Pain - TOP
Military Jet Takeoff
Instant Perforation of Eardrum
Intensity Level
0 dB
10 dB
20 dB
60 dB
70 dB
80 dB
98 dB
100 dB
110 dB
130 dB
140 dB
160 dB
Remember that a doubling in sound represents an increase of only 3dB
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Hearing Loss
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The ear can be easily damaged, by:
– Medical conditions
– Accidents
– Drugs
– Congenital conditions
– Social activities
– Prolonged exposure to high noise levels
Workers at risk of hearing damage are usually :
– Metal work
– Construction
– Quarrying
– Steel work
– Mining
– Noisy industries
Exposure above 90 db (A) is likely to cause damage
This is known as noise induced hearing loss
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Noise Induced Hearing Loss
Chronic NIHL
 Damage is caused to the sensitive
cells in the cochlea
 Occurs gradually from exposure to less
intense noise levels
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Noise Induced Hearing Loss
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Associated with exposure to high intensity,
continuous noise
The amount of sound that is capable of producing
cochlear damage and subsequent hearing loss is
based upon
– The equal energy concept
Therefore, it is the total sound energy delivered to
the cochlea that is relevant in predicting injury and
hearing loss
Both an intense sound presented to the ear for a
short period and a less intense sound that is
presented for a longer period will produce equal
damage to the inner ear
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Noise Induced Hearing Loss
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Chronic NIHL has two phases
Temporary Threshold Shift – TTS
– The first stage
– Brief hearing loss, ‘ringing in the ears’
– Completely resolves after a period of rest
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auditory fatigue
– Most studies indicate that no sensory cell
damage occurs
– After repeated exposure to noises
– A Permanent Threshold Shift - PTS will occur
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Noise Induced Hearing Loss
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Permanent threshold shift – PTS
– This is the second stage of chronic NIHL
– An irreversible increase in hearing thresholds
– Irreversible hair cell damage
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Once you have it, it is too late
– Sufferers report difficulty understanding speech
rather than hearing speech
– Particularly noticeable in environments with
significant background noise
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Noise Induced Hearing Loss
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An ‘normal’ audiogram
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Noise Induced Hearing Loss
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An audiogram showing the classic ‘dip’ in hearing performance
– Characterised by a loss of consonant discrimination
– Consonant sounds such as f, s, t, d, sh, and k are essential
to the intelligibility of speech
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Noise Induced Hearing Loss
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Socioacusis
– even people with quiet jobs may suffer
– Such non-occupational NIHL is also called
socioacusis.
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Sources of non-occupational noise include:
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Gunfire
Loud music
Open vehicles
Power tools
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The Law
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Noise at Work Regulations 1989
Place responsibilities
– employers
– Employees
– People who make and supply noisy machinery
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The regulations introduced three thresholds:
– First Action Level - 85dB(A)
– Second Action Level - 90dB(A)
– Peak Action Level - 200 Pascals or 140dB
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The sound at the ear is represented by (A)
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The Law
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First Action Level - LEP, d 85dB(A)
– When you have to raise your voice to be heard at 2 metres
– The employee must be trained
– hearing protection must be made available upon request
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Second Action Level - LEP, d 90dB(A)
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When you have to raise your voice to be heard at 1 metre
A noise reduction programme must be implemented
Areas must be marked
Employees must be provided with hearing protection,
which must be worn
Peak Action Level - 200 Pascals or 140dB
– This relates to sudden noise
– the duties are similar to those required by the second
action level
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The Law
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Employers duties
– Get the noise levels assessed by competent people
– Keep a record
– Where exposure is at, or above, any of the action levels:
 Inform personnel that there is a noise hazard
 Inform them of what to do
 Where the exposure needs to be controlled, quieten the
workplace, if this can be done
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Between the first and second action levels
– Provide ear protection (ear muffs or plugs)
– Inform workers of the risk to their hearing
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The Law
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Where use of protection is compulsory
– Ear protection zones should be marked
– Make sure that everyone who goes into a marked zone,
even for a short time, uses ear protection
– Check to make sure the control measures are working
– Make sure the equipment you provide is kept in good
condition
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If people work in noise at, or above, the second or
the peak action level
The regulations still require the reduction of noise
exposure by means other than ear protectors, as far
as this is reasonably practicable
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The Law
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Employees duties
– Wear the ear protection (earplugs or earmuffs) provided
– At the second or peak action levels might be reached
– Every entry into an area marked as an ear protection zone
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Use any other equipment the employer provides
– For example, if the machine is meant to have a silencer
fitted- don't take it off
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Look after any equipment provided under the
regulations
Report any equipment defects
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The Law –Changes Are Coming!
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The control of noise at work regulations 2005
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Come into force on 6th April 2006
Exposure limit values and action values
The lower exposure action values
– A daily or weekly personal noise exposure of 80 db (A)
– A peak sound pressure of 135 db
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The upper exposure action values
– A daily or weekly personal noise exposure of 85 db (A)
– A peak sound pressure of 137 db
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The exposure limit values
A peak sound pressure of 140 db
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Information, Instruction, And
Training
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What we need to tell you
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Exposure areas above the lower exposure action values
What we are doing to control risks and exposures
Where and how people can obtain hearing protection
How to report defects in hearing protection and noisecontrol equipment
– Duties under the noise regulations 2005
– What you should do to minimise the risk
 Such as the proper way to use hearing protection and
other noise-control equipment
 How to look after it and store it, and where to use it
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Exposure areas
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Exposure areas
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Information, Instruction, And
Training
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What we are doing to control risks and exposures
– Established advisory hearing protection zones
– Sourcing noise reduction blades
– Provide hearing protection
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Where and how people can obtain hearing
protection
– Freely available from dispensers or production manager
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How to report defects in hearing protection and
noise-control equipment
– Report to supervisor or manager
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Information, Instruction, And
Training
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Duties under the noise regulations
2005
– Wear the ear protection (earplugs or
earmuffs) provided
– Use any other equipment the employer
provides under the regulations
– Look after any equipment provided under
the regulations
– Report any equipment defects
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Information, instruction, and
training
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Earmuffs
– Make sure they totally cover your ears,
– Fit tightly and there are no gaps around the
seals.
– Don’t let hair, jewellery, glasses, hats etc
interfere with the seal.
– Try and keep the seals and the insides clean.
– Don’t stretch the headband too much – make
sure it keeps its tension.
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Information, Instruction, And
Training
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Earmuffs
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Information, Instruction, And
Training
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Earplugs
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They can be difficult to fit properly
Practice fitting them and get help if you are having trouble
They can look like they are fitted properly
Clean your hands before you fit earplugs, and don’t share
them
– Some types you use only once
– Others can be re-used and even washed
– Make sure you know which type you have
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Semi-inserts/caps
– Follow the same advice as for earplugs
– Make sure any headband keeps its tension
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Information, Instruction, And
Training
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Earplugs
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Information, Instruction, And
Training
Remember – hearing protection is
provided to protect you, if you do not
use it, you may lose it
 Remember – if in doubt, ask
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Objectives
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What is noise?
What is sound?
How do we hear?
What unit do we use to measure noise?
How we get Hearing Loss
The Law
– Employer duties
– Employee duties

PPE
– Where, what and when
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Noise at Work
Thanks for Listening
 Any questions
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