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Hansen – managing safely 1
Noise at WorkNoise at Work
Mark MallenGroup Health and Safety Manager
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IntroductionIntroduction
Noise at work and how it can affect you
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Objectives Objectives What is noise? What is sound? How do we hear? Measuring noise? Hearing Loss The Law
– Employer duties– Employee duties
PPE– Where, what and when
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Content Content
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?What is Noise?
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?What is Noise?
EffectsShort term
– Annoy– Distract
Long term– Deafness– Tinnitus– Noise Induced Hearing Loss (NIHL)
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SoundSound
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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SoundSound Like ripples on a pond – sound
pressure wave
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SoundSound
A Sound Wave– created by a vibrating object:
The vocal chordsA guitar string A machineTraffic The diaphragm of a radio speaker
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SoundSound
Air moves back and forth– The frequency of a wave
If a particle of air undergoes 1000 vibrations in 2 seconds– Then the frequency of the wave is 500
vibrations per secondThe unit of frequency is the hertz
(abbreviated Hz), where:– 1 Hertz = 1 vibration/second
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SoundSound
The human ear detects– Ranges between approximately 20 Hz to
20 000 HzAny sound less than 20 Hz
– InfrasoundAny sound above 20 000 Hz
– Ultrasound
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How do we hear Sound?How do we hear Sound?
The Ear– The outer ear
Collects and channels sound to the middle ear.
– The middle ear Transforms the energy of a sound wave into internal
vibrations via a bone structure.
– The inner ear The inner ear transforms these vibrations into nerve
impulses, which can be transmitted to the brain.
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The EarThe Ear
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The Outer EarThe Outer Ear
Consists of an earflap and an ear canalThe earflap protects the middle ear and
eardrum It also channels sound waves to the
eardrumSound is still a sound pressure waveAt the eardrum, the wave converts into
vibrations
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The Middle EarThe Middle EarAn eardrum
– A membrane, which connects to the hammer
Three tiny, interconnected bones– Hammer, anvil & stirrup– 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 EarThe Middle Ear 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 EarThe Inner Ear 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
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 EarThe Ear
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The CochleaThe Cochlea 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 NoiseThe Measurement Of Noise 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 NoiseThe Measurement of Noise
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 LevelsTypical Noise LevelsSource Intensity Level
Threshold of Hearing - TOH 0 dB
Rustling Leaves 10 dB
Whisper 20 dB
Normal Conversation 60 dB
Busy Street Traffic 70 dB
Vacuum Cleaner 80 dB
Large Orchestra 98 dB
Walkman at Maximum Level 100 dB
Front Rows of Rock Concert 110 dB
Threshold of Pain - TOP 130 dB
Military Jet Takeoff 140 dB
Instant Perforation of Eardrum 160 dB
Remember that a doubling in sound represents an increase of only 3dB
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Hearing LossHearing Loss 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 LossNoise Induced Hearing Loss
Chronic NIHLDamage is caused to the sensitive
cells in the cochleaOccurs gradually from exposure to less
intense noise levels
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Noise Induced Hearing LossNoise Induced Hearing Loss 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 LossNoise Induced Hearing Loss 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
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 LossNoise Induced Hearing Loss Permanent threshold shift – PTS
– This is the second stage of chronic NIHL– An irreversible increase in hearing thresholds– Irreversible hair cell damage
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 LossNoise Induced Hearing Loss
An ‘normal’ audiogram
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Noise Induced Hearing LossNoise Induced Hearing Loss 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 LossNoise Induced Hearing Loss
Socioacusis– even people with quiet jobs may suffer– Such non-occupational NIHL is also called
socioacusis. Sources of non-occupational noise include:
– Gunfire– Loud music – Open vehicles – Power tools
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The LawThe Law
Noise at Work Regulations 1989 Place responsibilities
– employers– Employees– People who make and supply noisy machinery
The regulations introduced three thresholds:– First Action Level - 85dB(A)– Second Action Level - 90dB(A)– Peak Action Level - 200 Pascals or 140dB
The sound at the ear is represented by (A)
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The LawThe Law 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
Second Action Level - LEP, d 90dB(A)– 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 LawThe Law
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 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 LawThe Law
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 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 LawThe Law
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
Use any other equipment the employer provides– For example, if the machine is meant to have a silencer
fitted- don't take it off Look after any equipment provided under the
regulations Report any equipment defects
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The Law –Changes Are Coming!The Law –Changes Are Coming! The control of noise at work regulations 2005
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
The upper exposure action values – A daily or weekly personal noise exposure of 85 db (A)– A peak sound pressure of 137 db
The exposure limit values A peak sound pressure of 140 db
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Information, Instruction, And Information, Instruction, And TrainingTraining What we need to tell you
– 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 noise-
control 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 areasExposure areas
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Exposure areasExposure areas
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Information, Instruction, And Information, Instruction, And TrainingTraining What we are doing to control risks and exposures
– Established advisory hearing protection zones– Sourcing noise reduction blades– Provide hearing protection
Where and how people can obtain hearing protection– Freely available from dispensers or production manager
How to report defects in hearing protection and noise-control equipment– Report to supervisor or manager
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Information, Instruction, And Information, Instruction, And TrainingTrainingDuties 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 Information, instruction, and trainingtraining 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 Information, Instruction, And TrainingTrainingEarmuffs
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Information, Instruction, And Information, Instruction, And TrainingTraining Earplugs
– 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
Semi-inserts/caps– Follow the same advice as for earplugs– Make sure any headband keeps its tension
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Information, Instruction, And Information, Instruction, And TrainingTrainingEarplugs
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Information, Instruction, And Information, Instruction, And TrainingTrainingRemember – 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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ObjectivesObjectives 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 WorkNoise at Work
Thanks for ListeningAny questions