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61 Cards in this Set
- Front
- Back
Noise |
Noise at Work Regulations 2005: Any audible sound Oxford English Dictionary: A sound, especially one that is loud or unpleasant or that causes disturbance Sound: Vibrations or pressure changespassing through a medium, usually air |
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Sound |
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Sound Intensity and Decibels |
Intensity is sound power per unit area A measure of the flow of sound energy - units W/m2 Lowest value detected by human ear is 10-12 W/m2 Highest likely to be encountered is 1 W/m2 Very large range so Decibel (dB) used for convenience Logarithmic scale Usually expressed as sound pressure level |
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Decibel Scale |
Threshold of pain - 130 Noisy factory - 90 Busy traffic - 70 Normal conversation - 60 Soft whisper - 20 Threshold of hearing - 0 Logarithmic scale, so increase of 3 dB means doubling of sound intensity |
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Adding Decibels |
If adding similar values, add 3dB e.g. 90dB + 90 dB = 93dB If adding dissimilar values, use graph or table |
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Frequency |
Pitch of note Sounds usually a mixture of frequencies Human hearing range given as 20Hz to 20KHz Frequencies often divided into octave bands, represented by central value Frequency important in control, and selection of hearing defenders |
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Frequency - Octave Band |
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A-Weighting |
Tones of the same pressure level do not sound equally loud to the ear, nor do they have the same potential for causing hearing loss
High frequencies sound louder and are more likely to cause damage Low frequencies sound quieter and are less likely to cause damage A- weighting compensates for this differenceAfter A-weighting is adopted - dB(A) |
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C-Weighting |
A-weighting is not appropriate at high noiselevels Ear becomes better at hearing high/low frequencies Almost linear response Used for peak values - dB(C) |
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Noise Dose |
Noise measurements usually averaged over a time period Known as Leq: L can be any length of time Control of Noise at Work Regulations refer to Daily noise exposure: Averaged over 8 hour period Known as daily noise exposure or LEP,d Also make reference to peak values |
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Mechanism of Hearing |
Vibrations directed by pinna into auditory canal Eardrum vibrates Vibrations carried across middle ear by ossicles to cochlea Vibrations pass through fluid in cochlea in inner ear Detected by sensory hairs (stereocilia) Conveyed to brain by auditory nerve |
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Noise - Adverse Health Effects |
Nuisance and stress Tinnitus Noise induced hearing loss (NIHL) Temporary threshold shift - reversible damage (auditory fatigue) Permanent threshold shift - failure of her cells to respond to frequencies Acoustic trauma TTS & PTS (NIHL) generally occurs in the 4000hz octave band - 4K dip |
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Acoustic Shock |
Sudden, unexpected loud sound through headset May be below Action Values No loss of hearing Symptoms: Early: tinnitus, dizziness, nausea Intermediate: headaches, fatigue, anxiety Late: hypersensitivity, anxiety returning to telephone work Controls: Protection devices Reduce background noise Prompt repair of equipment Manual control of voice levels |
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Audiometry - Basic Principles |
Routine health surveillance Health surveillance required if risk assessment identifies risk to health Guidance suggests this is regular exposure above upper exposure action value Shall include test of hearing – audiometry Used as base line assessment Also implications in Civil Law |
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Audiometry - Method |
Details given in standard (EN26189:1991) Quiet environment No significant noise for 16 hours previously Pure tones played - subject presses button if heard Software produces graph (audiogram) |
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Audiometry - Audiogram |
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Audiometry - Age Related Hearing Loss (Presbycusis) |
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Audiometry - Action to be Taken |
Category & Action 1: Acceptable: No action required 2: Mild hearing impairment: Formal notification Reinforcement of training and importance of controls Good practice to issue copy of audiogram 3: Poor hearing: Referral to medical practitioner 4: Rapid hearing loss Referral to medical practitioner |
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Control of Noise at Work Regulations (CNWR) 2005 - Regulation 4 & 5 |
Reg. 4: Exposure action values and exposure limit values Reg. 5: Assessment to be carried out where exposure likely to reach lower exposure action value (80 dB(A)) To cover: Level, type, duration of exposure Manufacturers information Availability of alternative equipment Results of health surveillance Availability of PPE Recorded and reviewed |
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CNWR - Action Values |
Lower Exposure Action Value - 80 dB(A) LEP,d/Peak 135 dB(C): Make PPE available Provide information and training Assessment Upper Exposure Action Value - 85 dB(A) LEP,d/Peak 137 dB(C): Reduce ALARP by means other than PPE Hearing Protection Zones Health surveillance (audiometry) |
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CNWR - Limit Values |
Upper Exposure Limit Value - 87 dB(A) LEP,d/Peak 140 dB(C): Not to be exceeded |
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CNWR - Limit Values Exceeded |
Exposure is not permitted above exposure limit value (87dB(A)) If exposure does occur, employer must reduceexposure to noise to below the exposure limitvalue Identify the reason for that exposure limit value being exceeded Modify the organisational and technical measures to prevent it being exceeded again |
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CNWR - Regulation 7 |
Hearing protection: To be made available at or above lower exposure action value Must be worn above upper exposure action value (if cannot be controlled by other means) Hearing Protection Zones: Designated and signage displayed Employer to maintain PPE and ensure use SFARP (Reg 8) |
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CNWR - Regulation 9 & 10 |
Reg.9 - Health surveillance: Where the risk assessment indicates that there is a risk to health Risk to health: If there is regular exposure above the upper exposure action value Must include a hearing test (audiometry) If hearing damage is identified then the employer must refer the individual to a medical practitioner. Reg. 10: Employer to provide information, instruction and training where lower exposure action value is reached |
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CNWR - Employees Duties |
To comply with the employers arrangements for controlling noise To use hearing protectors and noise control equipment To take care of such equipment, and to report any defects (all Reg 8) To co-operate with employer and attend hearing tests (Reg 9) |
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Noise Measurement - Basic Principles |
Sound Level Meter: Simple measures dB or dB(A) at a moment in time Integrating if measures Leq Leq - equivalent continuous noise level Need to measure A-weighted Leq (LAeq) Need C-weighting for peak levels Need to be calibrated each time they are used |
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Noise Measurement - Classes of Device |
Lower the class of SLM, higher the quality Class 0 - Research Class 1 - Laboratory/Field Class 2 - General Field Class 3 - Non integrating Calibrators also different classes Selection depends on objectives of survey Increasing accuracy and response from Class 3 to Class 0 Class 1 or 2 for occupational safety measurements |
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Noise Measurement - Personal Dose Meters & Frequency Analysers |
Personal dose meters: Worn by person exposed in hearing zone Measures actual dose for referenced time period Frequency analysers: Measure sound pressure levels at particular frequencies Required for accurate assessment of hearing defenders Combination of above and accessories e.g. storage of data, print outs, software |
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Workplace Noise Survey |
Planning: Objectives and scope Information sources: Previous assessments Employees Manufacturers information Complaints Selection of measuring equipment including calibrators Battery check Number of employees exposed/duration Areas to be surveyed Recording of data Route Safety issues/risk assessment |
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The Ready Reckoner - Estimate (L108) |
Estimate of noise exposure: Try this: 1) 30 mins spent working on a grinding machine - manufacturers info says 95dB 2) 3 hours working in yard with vehicles - check suggests 85dB 3) 1.5 hours in office - check suggests 80dB 4) 2 hours back in yard at 85dB
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Estimating LEPd - Static Measurements |
Static measurements taken at operating positions at each machine Static measurements taken during normal operation Sound measured as LAeq Use integrating SLM Note the time operator spends at each machine Calculate using points system/HSE spreadsheet Assess or assume insignificant exposure during breaks |
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NoisePropagation |
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Effect of Distance - Inverse Square Law |
Inverse square law: Refers to decrease in noise energy (and other energy forms) as it moves away from a point source Energy/intensity is proportional to 1/d2* (d = distance) At 1 unit distance = 1/1 2* = 1 At 2 units distance = 1/2 2* =1/4 At 3 units distance = 1/3 2* =1/9 Note: 2* denotes squared |
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Effect of Distance - Doubling Distance |
Doubling of distance means a reduction of noise of 6 dB |
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Controlling Noise - General Principles |
Eliminate at source, or control so far as is reasonably practicable at source (e.g. by relocation, redesign and maintenance) Control along the transmission path (e.g. by using isolation, barriers and enclosures) Control exposure at the receiver (e.g. by enclosures, acoustic havens, hearing protection zones and PPE, limiting exposure time, audiometry) |
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Controlling Noise - Methods (1) |
Engineering controls Selection of equipment (presses instead of hammers) Location of pipe-work and ducting Reduce operation speeds Distance/orientation Maintenance (balancing, sharpening, tightening) |
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Controlling Noise - Methods (2) |
Enclosure (noise enclosures) Isolation (noise havens, springs to absorb energy) Silencers (air movements/absorptive reactive) Lagging Damping (pads, stiffening) Screens Absorption PPE |
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Acoustic Enclosure - Design (1) |
Keeps noise in Heavy outer wall (plasterboard and brickwork) Inner lining of acoustically absorbent material Absorbent covered in protective mesh Flexible pipes to form vibration breaks Services in through ground Inspection door double/triple glazed Access panels for maintenance |
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Acoustic Enclosure - Design (2) |
Access doors airtight Any joints to outside sealed Motors on dampers Machines covered in enclosures Avoid contact between equipment and walls Sound absorbent material on floors Silencers on any ventilation exits Self-closing doors Exterior controls |
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Acoustic Haven |
Keep noise out Air conditioned/lighting/thermal comfort/workstations Viewing windows Emergency response (fire alarms etc) Above workplace for better view External surface reflective Internal acoustic absorbent Internal walls cleanable Isolated from floor and ceiling Double/triple glazed Air supply through lagged pipework |
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Hearing Protection - Basics Principles (1) |
Selection is critical Matched to noise characteristics Will only be effective when used Types and specifications: Ear defenders Semi-inserts Earplugs Active hearing protection |
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Hearing Protection - Basics Principles (2) |
Mean attenuation values atfrequency bands 63-8000 Hz Subjective test - 16 test subjects Standard deviation values for each (+/- 84%) Assumed protection values at each frequency ( = mean – one standard deviation) HML (high, medium, low) values SNR (single number rating) |
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Hearing Protection - Selection |
Use HML (apply formula) Use SNR Octave band frequency |
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Hearing Protection - Single Number Rating (SNR) |
Simple guide to hearing protection required: Noise Level dB(A) & SNR Required 85-90 - 20 or less 90-95 - 20-30 95-100 - 25-35 100-105 - 30 or more |
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Vibration - Basic Principles |
Oscillating movement of a fixed point due to applied energy |
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Vibration - Basic Terms |
Displacement (amplitude) – maximum distance moved from the point of oscillation Frequency – number of complete oscillations per second (Hertz) Velocity – speed of the oscillating object at a fixed point in time (m/s) Acceleration – maximum rate of increase in speed (m/s2 ) Magnitude – Vibration at Work Regulations 2005 = acceleration |
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Measurement of Vibration |
Accelerometer Average (root-mean-square) of acceleration in three planes Weighting given to most harmful frequencies (8-20 Hz) Expressed as A(8)- daily exposure |
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Hand Arm Vibration Syndrome (HAVS) |
Impaired circulation to fingers - blanching (white finger) Numbness in fingers, reduced sensitivity, tingling Loss of dexterity Loss of grip strength Pain (especially in cold weather) Infection/gangrene Carpal Tunnel Syndrome and associated symptoms |
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Whole Body Vibration |
Range of health effects Back pain Nausea Gastrointestinal upsets General feeling of discomfort, includingheadaches Loss of equilibrium (balance) Abdominal pain |
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Factors Contributing to Risk |
Damage depends on: Vibration magnitude Vibration frequency Duration of exposure Individual susceptibility (diabetics/smokers more at risk) External temperature Tightness of grip |
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Control of Vibration at Work Regulations (CVWR) 2005 - EAVs & ELVs |
Exposure limit values and exposure action values: Hand-arm vibration: EAV 2.5 ms-2 A(8) ELV 5.0 ms-2 A(8) Whole body vibration: EAV 0.5 ms-2 A(8) ELV 1.15 ms-2 A(8) A(8) vibration dose averaged over an 8-hour shift |
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CVWR - ELV |
Must not be exceeded If exceeded then: Reduce exposure to vibration to below the limit value Identify the reason for that limit being exceeded Modify the measures taken to ensure it does not happen again |
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CVWR - ELV |
Provide appropriate health surveillance (Regulation 7) Provide adequate information, instruction and training (Regulation 8). |
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CVWR - Risk Assessment |
Reg 5: Risk assessment required if employees are exposed to risk due to vibration Assessment to consider: The frequency and magnitude of vibration The health effects of exposure to vibration Any information provided by the manufacturers of work equipment The availability of replacement equipment designed to reduce exposure to vibration Specific working conditions such as low temperatures appropriate information obtained from health surveillance |
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Estimating Daily Exposure |
Graph Points system |
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Hand Arm Vibration - Controls |
Automation Change of work method Modify/use alternative equipment Purchasing policy Maintenance Monitor exposure and enforce limits Job rotation Instruction and training Health surveillance PPE - gloves to keep hands warm Warm temperatures |
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Hand Arm Vibration - Health Surveillance |
Tier 1 - A short questionnaire used for new workers Tier 2 - A short questionnaire for employees already exposed Tier 3 - This involves a HAVS health assessment by a qualified person, if the assessment shows that the employee has HAVS, Tier 4 will apply Tier 4 - Formal diagnosis by occupational health physician Tier 5 - Optional: referral for further tests |
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Hand Arm Vibration - Tier 3/4 Assessment |
Grip strength Muscular dexterity Vascular Finger rewarming after cold provocation Finger systolic blood pressure Sensorineural Vibrotactile perception threshold Thermal perception threshold |
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Hand Arm Vibration - Stockholm Workshop Scales (Sensorineural) |
Stage - Description: 0SN - Vibration exposed & no symptoms 1SN - Intermittent numbness with or without tingling 2SN - Intermittent or persistent numbness, reduced sensory perception 3SN - Intermittent or persistent numbness, reduced tactile discrimination and/or manipulative dexterity |
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Hand Arm Vibration - Stockholm Workshop Scales (Vascular) |
Stage - Grade - Description: 0 - No grade - No attacks 1V - Mild - Occasional attacks affecting tips of one or more fingers 2V - Moderate - Occasional attacks affecting distal and middle (rarely also proximal) phalanges of one or more fingers 3V - Severe - Frequent attacks affecting all phalanges of most fingers 4V - Very severe - As in stage 3 with trophic skin changes in the fingertips |
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Whole Body Vibration - Controls |
As for HAVS e.g. maintenance/automation etc Specific examples: Drive vehicles more slowly Ergonomic design of vehicle cabs Mount seats on springs or compression pads/ provide cushions Provide rubber mats for standing tasks |