Noise at WorkBy Mark Cooper

28th February 2006

HSE Research suggests that over 170,000 people in the UK suffer either hearing loss or tinnitus through excessive exposure to noise at work

and this suffering is preventable

We will look atHow we hearDamage caused by noiseHearing protection the total solution?Introducing noise legislationThe new Control of Noise at Work Regulations 2005Aspects of noise nuisance

Damage to the sensory cells

The concept of a noise doseHearing damage is related to the Noise Dose, which is a combination of the TIME and LEVEL of exposure

Some dose equivalentsThe following noise levels and exposure times are equivalent to a dose of 80 dB for 8 hours:

Equivalents to 80 dB for 8 hours:Road breaker @ 89 dB for 1 hrConcrete crusher @ 92 dB for 30 minutesHammer drill @ 101 dB for 4 minutesFettling chisel @ 110 dB for 30 seconds!

The new Noise at Work Regulations 2005

The new Noise at Work Regulations 2005Due to Physical Agents (Noise) Directive (2003/10/EC)Replace Noise at Work Regulations 1989Come in to force on 6th April 2006Delayed introduction for places of music & entertainment until 6th April 2008

Noise level - terminologyNoise levels in the Regulations are expressed either as:

8 hr noise dose equivalents LEP,d

Peak noise level

Peak noiseWhat is peak noise?How is peak noise assessed?

Implications of new regulationsA lot more workplaces will come within the action levelsAudiometry will have to be conducted on many more workersEmployers will have to look for more ways to control noise at source rather than simply relying on ear protection

Noise Exposure equivalent levels

Noise Measuring EquipmentCategories of equipmentType 0 laboratory gradeType 1 Highest field gradeType 2 Lowest field gradeType 1 or 2 normally used for noise at work measurementsEquipment may be hand-held sound level meter (SLM) or dose meterEquipment should be calibrated before and after each reading and periodically under laboratory conditions

Noise measuring equipment

Noise measuring equipmentHand-held SLM vs Dose meterWhy is the hand-held method preferable?

Calculating protection from hearing protectionOctave band methodMost accurate, but requires octave band dataMost complicated calculationHML (High, Medium, Low) methodSimple calculation, only requires A-weighted and C-weighted Leq levelsPreferred method in most circumstancesSNR (Single Number Rating) methodOnly needs C-weighted Leq levelsHSE calculator

any questions?

The Management of Hand-Arm Vibration

HSE/Medical Research Council4.8 million people in UK regularly exposed to HAV

Includes 1.2 million working above HSEs current recommended action level

HSE/Medical Research Council300,000 people may have cold-induced finger blanching (VWF) due to exposure to vibrationMost common prescribed industrial disease in the UK with about 3000 new disablement benefit cases each year to Department of Work & Pensions

Civil Action for HAVS Examples of compensation cases:200,000 award to a tree surgeon employed by Liverpool CC (1998)143,000 award to British Gas fitter: total of 430,000 to six fitters (1998)

Compare this to the average 6000 compensation award for noise induced hearing loss

Hand arm vibration - effectsHAVS (Hand arm vibration syndrome)Effects:VascularNeurologicalmusculoskeletal

HAVS SymptomsVascular (Vibration White Finger, VWF)Finger blanching (nb. Although vibration causes the condition, this symptom is precipitated by cold, not vibration)Painful red throbbing on re-warmingPermanent discolouration of the fingers after many years exposureSimilar symptoms may occur endogenously, i.e. primary Raynauds Syndrome

Trophic finger blanching

HAVS SymptomsNeurological componentTinglingNumbnessLoss of sensationLoss of manual dexterityPainful parasthesiae at night

HAVS SymptomsMuscular & soft tissue componentMuscle fatigue & loss of grip strengthCarpal Tunnel Syndrome

Skeletal componentDisorders of the bones (cysts & vacuoles)Joint disorders of the upper arm

HAVS SymptomsClassification of symptomsStockholm Workshop ScalesThe preferred system in determining damage claims

Stockholm Workshop Scales

Vascular componentStageGradeDescription0No attacks1VMildOccasional attacks affecting only the tips of one or more fingers2VModerateOccasional attacks affecting distal and middle phalanges of one or more fingers3VSevereFrequent attacks affecting all phalanges of most fingers4VVery severeAs in Stage 3 with trophic changes in the fingertips

Stockholm Workshop Scales

Sensorineural componentStageDescription0SNVibration-exposed, but no symptoms1SNIntermittent numbness, with or without tingling2SNIntermittent or persistent numbness, reduced sensory perception3SNIntermittent or persistent numbness, reduced tactile discrimination and/or manipulative dexterity

What jobs are prone to cause HAVS?Construction (esp. roads & railways)Working with concrete productsForestryFoundriesHeavy engineeringMines & quarriesPlate & sheet metal fabricationPublic utility workers

Examples of tools that can cause excessive hand arm vibration dosesRotary tools e.g.ChainsawsHand-held grinders & sandersLawnmowersStrimmersPercussive tools, e.g.Breakers, road drillsHammer drillsPower hammers and chiselsRiveting hammers & bolstersNeedle guns

Factors which increase risks of HAVS

Sensitivity of hand to vibration

Sensitivity of hand to vibration2 4 6 8 10 16 32 64 125 250 500 1K1.21.00.80.60.40.20Frequency (Hz)Relative sensitivity

Vibration Dose - A8HAVS damage is dose-relatedThe A8 is defines daily vibration exposure as the 8-hr energy equivalent frequency-weighted rms acceleration (analogous to the LEP,d for noise exposure)

Daily vibration exposure, A(8)Where ahv is an rms value representative of the measuredvibration magnitude,T is the total daily exposure duration, andT0 is the reference duration of 8 hours (28800 seconds)

Control of Vibration at Work Regulations 2005Sets two levels for hand-arm vibration

Exposure Action Value of 2.5ms-2 A8Exposure Limit Value of 5ms-2 A8

Vibration Regulations requirementsReduce vibration risk and exposure to a minimumAssess risk and exposure levelsWhen EAV is exceeded, plan and implement programme of measures to reduce exposureWhen EAV is exceeded, provide appropriate health surveillanceKeep exposure below ELVProvide information and training for vibration-exposed employees

Transitional arrangementsThe Regulations allow transitional period of up to 5 years for meeting ELV levels (up to 9 years for agriculture and forestry)Applies only to equipment supplied before 2007No transitional period in respect of EAV, but does allow time to implement changes in the longer term

Establishing ahv the vibration total value

BS EN ISO 5249 -1Vibration Total ValueWhere ahwx, ahwy and ahwz are the measured weighted rms vibration magnitudes of each axis

Assessment & control first stepsTo measure, or not to measure, that is the question

Assessment of exposureAssessment is the first step, but need not necessarily involve taking measurementsInformation may be obtained on vibration levels:Database information- commercially available in-use data for a range of operating situations Public web-based databases of in use dataManufacturers emission data

Emission dataMachinery Directive (98/37/EC) (enacted in UK by Supply of machinery (safety) regulations 1992 as amended) requires manufacturers & suppliers to:Design & construct machinery to state of the art for safe operationProvide instructions and information regarding any residual risks (including vibration)Specifically, must provide declaration of actual frequency-weighted acceleration value if it exceeds 2.5ms-2

So why not just use manufacturers emission data to determine exposure?Emission data based on standardised test codes (e.g. BS EN ISO 8662 series for pneumatic tools)Test codes designed to allow repeatability in different laboratoriesTherefore based on artificial use of the toolEmission data is therefore a poor reflection of actual use levels of vibration

Measuring vibrationIt might be necessary to take direct measurements iffairly reliable information is not available from other sources, orthe use of the equipment is non-standard and therefore other data obtained is not valid,

Measuring vibrationBefore embarking on measurement exercise:If equipment is a percussive tool and is used for more than a few minutes a day, orEquipment is a rotary tool and is used for more than hr per dayassume that you are above the EAV and look at obvious controls, e.g.Do we need to use the tool at all?Can the tool be replaced with low-emission alternative?

Measuring vibrationUses accelerometers attached to equipment at point in contact with handMeasure all three axes, x, y & zMay use single accelerometer three times, orUse triaxial accelerometer (3 accelerometers mounted in the three planesProne to experimental error

Error in vibration measurementMounting the accelerometer the main source of error

Hand held accelerometerThrough-the-fingers or ring-mounted poor response may cause amplification

Other sources of errorOperator the skill, technique, experience of the operatorTask is the task performed during measurement representative of a whole days exposure?Tool or machine changes of emission due to wear of cutting surfaces etc.Exposure time assessment estimate of actual trigger time crucial to exposure assessmentMeasurement time- long enough to get representative readings?Instrumentation inherent limits on accuracy; electrical noise (esp. from cables)

Measurement errorPitts (2003) estimates an overall uncertainty for best practice evaluation to be in the range -19% to + 22%BS EN ISO 5349-2 estimates typical uncertainties on A(8) value to be in the range 20-40%

Elements of a control programmeChange process to avoid HAVE.g. using a JCB mounted pecker breaker rather than pneumatic breakersRemoving old paint from steel with grit or water blasting instead of a needle gunChange process to reduce HAVE.g. improving casting process to reduce need for fettlingSee HS(G) 170 Vibration SolutionsUse vibration-reduced toolsMore and more becoming available look at their vibration emission data to compare types

Elements of a control programme (2)Train workers to use tools properlyPoor technique can increase vibration transmission significantlyPut in procedural controlsRegular work breaks (with facility for hand-warming if necessary)Limitation of exposure time Time to reach EAV = (2.5/Ahv)2 x 8 (hours)Time to reach ELV = (5.0/Ahv)2 x 8 (hours)

Elements of a control programme (3)Provide workers with information on risks and controlsHSE Hard to handle videoWritten safe operating procedures & work instructionsProvide health surveillanceExamination by occupational nurse/doctorSelf-reporting questionnaire (e.g. HSG 88)PPE? Dont bother with Anti-vibration gloves they dont workAnd of course supervision

Hear we can see the damage caused to the sensory cells by excessive noise. This damage is irreparable and permanent.

Noise-induced hearing damage doesnt just make things sound quieter. Some tones are reduced more than others Typically these tones are the S and T sounds that make words easy to understand. After years of exposure to high levels of noise, the effect becomes worse and may include tinitus, which is a constant annoying noise in the ear, such as hissing, ringing or buzzing. This simulation demonstrates what you might hear if you had noise-induced hearing loss.

Run demonstrationWhen someone is exposed to very high noise levels, day after day, say 100dB, they may experience hearing loss in as little as a year. If the level goes as high as 140dB, then hearing loss can be almost immediate, and the eardrums themselves might burst. This is what we call Acoustic Trauma. However, industrial noise, including construction noise, is normally at levels between 80 and 95dB. It is known that the risk of hearing loss becomes significant at 80db. This means that someone exposed to at least 80db for the majority of their working day, most days of the week, might expect to have some loss of hearing in the future.So the potential for damage is a combination of the level of noise and the time for which someone is exposed. We normally try to compare noise doses to an 8 hour dose, as this is the normal working day. As the 80dB dose is the threshold of damage, as we have seen, and is also the First Action Level in the revised Noise at Work Regulations, which come out soon, lets use this as our dose for comparison So you can see that a worker does not necessarily need to be exposed for long periods of the day to be at risk. The longer the exposure, or the higher the level, the greater the risk.