Noise at Work Regulations Mick Gray MRSC, LFOH, ROH. MWG Associates Ltd
The Issue NIHL is a significant occupational disease 170,000 people in the UK suffer deafness, tinnitus or other ear conditions as a result of exposure to excessive noise at work Health and Safety Executive 3 rd European workers are exposed to potentially dangerous levels of noise for at least a quarter of their working time European Agency for Safety and Health at Work the most prevalent, irreversible industrial disease - World Health Organisation
Programme Basic Noise Terminology The Control of Noise at Work Regulations 2005 Instrumentation for Workplace Noise
Basic Noise Terminology
An introduction to noise and sound What is noise? Noise is usually defined as unwanted sound But unwanted by whom? Let us consider the more general case of sound
Basics of Noise Terminology One of the 5 human senses - sight, touch, taste, smell, hearing Pressure variations in the air caused by something moving detected by our ears and turned into electrical impulses ear is divided into 3 parts, outer, middle and inner ear brain sorts them out into some form of meaning
The physics of hearing we hear sounds over a wide range of frequencies measure frequency in Hz Hz is short for Hertz or cycles per second (cps) we hear sound over a wide range of levels measure levels in db db is short for decibels we hear sound over a wide range of times measure time in seconds, minutes or hours
db Scale
What do we hear? Air pressure fluctuations are caused by vibrating objects or by air flows low speed variations cause low frequency sounds few tens of variations per second high speed variations cause high frequency sounds few thousands of variations per second variations are called frequency or tone or pitch limits of normal healthy hearing is about 20 to 20,000 Hz in the very best case
The inequality of human hearing - 1 We do not hear all sounds with equal intensity our ears are less sensitive to some frequencies than others this is more noticeable at the lower frequencies of sound consider some sounds as examples Hum of power transformers, air conditioning, etc
The inequality of human hearing - 2 our hearing is non-linear unlike the response of a hi-fi amplifier it is also non-linear with the loudness (or strength) of the sound research has established 3 main areas of interest associated with noise measurements standardized correction curves have been written into the way measurements are carried out
The equal loudness curves Lowest curve shows the threshold of hearing (audibility) for normal adult male Phon curves
Frequency weighting curves -1 For low level measurements correction curve is quite steep the A weighting curve for medium level measurements the correction is less steep the B weighting curve for high level measurements the correction is only at the extremes the C weighting curve
The frequency correction curves The A curve is at 40 Phons, the B curve is at 70 Phons, the C curve is at 100 Phons
The standard broadband frequency weightings for noise measurements
Frequency weighting curves - 2 for some measurements the true or uncorrected frequency response is needed (sometimes called Linear or un-weighted or All- Pass) this can be different for different manufacturers and for different instruments from the same manufacturer depending on microphone fitted the Z weighting curve sets limits of 20 to 20kHz
What do we hear? How loud is it? Very wide range of sound pressures experienced Sound pressure is measured in Pascals (N/m 2 ) lowest values few tens of micro Pascals (10-5 Pa) highest values are about 100/200 Pa this is a range of at least 10 6 this is a ratio of over 1 million to 1!!
What range do we hear? If we measured this like we do with temperature or length,.. We would need a tape measure that could measure 1 mm and 1 km!! (1 thou to 83 ft) This would be very difficult to express results if we had to use absolute units of sound pressure, so.
How do we measure sound? We use a relative scale rather than an absolute scale we say a sound is bigger (or smaller) than another sound by a certain amount logically we would choose a pressure of 1 Pa (like 1 Volt for electrical signals) but then we would end up with a scale of smaller and bigger values, so.
How do we measure sound? We choose the lowest pressure that the normal ear can hear as our reference point in this way all other sounds are always bigger than that sound First we need to have a reference pressure level 20 micro Pascal at 1 khz has been internationally agreed
The dreaded decibels!! Actual equation used to find the db value of a given sound pressure is found from - db = 20 log (P/P ref ) P ref = 0.00002 Pa because of the logarithmic nature of the db scale 70 db + 70 db (does not =) 140 db 70 db + 70 db = 73 db
The maths of db s The reference sound pressure corresponds to the lowest sound that can be normally heard now we refer all other sounds to this level a sound 10 times more would be +20 decibels (db) a sound 100 times more would be +40 db a sound 1000 times more would be +60 db a sound pressure twice as much would be 6 db (Note that a sound with twice the noise energy increases by 3dB)
The R.M.S. time constants We use the result of the R.M.S. circuit to see the noise level on the display for steady noises we use the time averaged levels slow (1 sec), fast (1/8 sec), impulse (1/32 sec) these settings are standardized on meters to allow comparisons to be made There is a Peak setting on some meters to capture the true highest level (equivalent to <1/10,000sec)
What do we measure? Definitions of some of the popular noise units as we come across them in the sessions later on Instantaneous sound pressure level maximum sound pressure level minimum sound pressure level peak sound pressure time average sound pressure level L L mx L mn L pk L eq
Example of the steady level 90 L AEQ = 83 db L A 80 70 TIME
How do we state the result? Need to specify the frequency weighting A, C or Z (non) need to specify the time weighting S, F or I
Expression of typical noise result For example, the noise level from a source - maximum A weighted Fast sound pressure level was 85 db over a 3 min period written as L AFmx = 85 db (3 min)
Lepd for a 4 Hour Shift 90 Steady LAeq 90dB 89 88 87 86 85 1 2 3 4 5 6 7 8 9 10 11 12 LAeq LAeq Lepd Noise is measured for 4 hours Energy is spread over 8hrs Therefore Lepd is 87dBA
Lepd for an 8 hour Shift 90 88 86 84 82 80 1 2 3 4 5 6 7 8 LAeq LAeq Lepd 8 hour LAeq = Lepd Steady noise of 90dBA for 8 hours = 90dBA Lepd
Lepd for 12 hour shift 94 93 92 91 90 89 88 87 86 85 1 2 3 4 5 6 7 8 9 10 11 12 LAeq LAeq Lepd Employee is exposed to 4 hours extra energy, therefore Lepd is higher than measured LAeq 12 hours of steady 90dBA = Lepd of 92dBA
The peak level limit Although L EP,d is an 8 hours value. But very high impulses of noise can cause instant damage to hearing. So instruments have peak hold function to measure any impulsive noises (L CPK ). Only has to be exceeded once to be considered over action level.
Introduction to noise Conclusions noise (sound) has three dimensions frequency level time Must measure properly to ensure you get the correct values
Physical Agents (Noise) Directive Directive 2003/10/EC The Control of Noise at Work Regulations 2005
Below first action level Employer must: Reduce risks to lowest practicable level Keep records and make them available including audiometry (if done) Buy quiet
Above first action level Employer must: Identify all employees at risk Put up signs Review if any changes to noise levels Repeat assessment <2 years Inform employees of risk Provide choice of PPE on request (first aid) Provide training / education Noise Control
Above second action level Employer must: Demarcate as Ear Protection Zones PPE must be used at all times Noise control to reduce exposure If Lepd is over 95dBA then must use octave band method to check if hearing protection is effective Note: For peak action level, take the same action as for second action level
Why the changes? Even under current regulations many people are still exposed to unacceptable levels of noise. 14% of population exposed to noise in the workplace will suffer some long term damage New regulations give new emphasis
What is new emphasis? Main goal is control of noise risk Risk assessment to establish what needs to be done Controls known to work should be implemented PPE in place Other systems in place Maintenance Training Health surveillance
Action level changes First action level: Becomes Lower Exposure Action Value 80dB(A) L EP,d (Reduction of 5dB) New: 112 Pascals (L CPK = 135dB) Take the same actions as first action level in current regulations
Action level changes Second action level: Becomes Upper Exposure Action Value 85dB L EP,d (Reduction of 5dB) 140 Pascals (L CPK = 137dB) Take the same action as second action level in current regulations
Exposure limit value 87dB(A) L EP,d exposure limit 140dB L CPK exposure limit (200 Pascals) Is the maximum permissible estimated operator noise dose whilst wearing (and not wearing) hearing protection Value at the ear after taking into account any PPE Therefore necessary to calculate effectiveness of PPE NOT a target, but minimum acceptable Target these individuals first
Peak Action Level Second Action Level First Action Level 140 db 90 dba 85 dba 140 db Peak Limit Value at ear 137 db Peak level at Upper Exposure Action Value 135 db Peak level at Lower Exposure Action Value 87 dba Exposure Limit Value at ear 85 dba Upper Exposure Action Value 80 dba Lower Exposure Action Value Currently (86/188/EEC) d B From April 06 - (2003/10/EC)
Weekly noise exposure level Calculate if there is significant variation of dose on a daily basis Take log average of estimated daily doses Apply action levels as normal
Audiometry Employees over the second action level have the right to a hearing check (audiometric test) As a preventative measure individuals who may be susceptible to noise below this level should also be tested e.g. those with previous damage.
Risk Assessment Assess risks to Health and Safety Done to identify actions to reduce risks Necessary when lower action levels likely to be exceeded Should assess exposure, measure if likely to be above second action levels
New exposure tool Exposure points have replaced nomogram Converts Laeq or L CPK into exposure points Converts EP into L EP,d Meant to allow easier assessment of higher risk activities
The competent person? Competent person will not appear in regs Risk assessment/control measures to be competently planned and carried out Rely on expert intermediaries for advice and services where necessary Guidance will be given to judge when advice is needed
Need to measure for correct hearing protection where necessary Octave Band Method Needs frequency analyser 31.5Hz - 8KHz High, Medium and Low (HML) Method Needs C and A weighted L EQ Simplified Noise Reduction (SNR) Method Needs C weighted L EQ Octave band is the preferred method
Summary Asses the risks Decide on control measures Qualitatively or quantitatively, with due regard to precision Reduce risks for all employees Hearing protection for residual risks Health surveillance
Implications Cost New assessment Review PPE Increase noise control Action plan Time
When will it be implemented? The Control of Noise at Work Regulations 2005, ISBN 0110729846 6 th April 2006 http://www.hse.gov.uk
Instrumentation for Workplace Noise Assessments
S.L.M. or Dosimeter? Two main types of instrument are used to perform workplace noise assessments Sound Level Meter (SLM) Dosimeter
When to use an SLM Is the preferred method of measuring Noise at Work At the ear (10-15cm) pointing at noise source Measure both ears Can only do this easily for stationary jobs Need to measure for each job and calculate Lepd
When to use a Dosimeter Dosimeters are easier but have to be aware of possible errors Tampering Body reflections Use Dosimeters for: Mobile workers Complex work patterns Walk through management Research shows will get a higher reading with dosimeter compared to SLM
Instrument Accuracy Different accuracies are available: Type 0 (laboratory standard) Type 1 (precision grade for consultants/environmental) Type 2 (general purpose grade) These Types are also knows as Class Type 2 is minimum required for Noise at Work
Other considerations Instruments must be field checked before use Use an acoustic calibrator, ideally in area where they are to be used Must have a valid calibration certificate UKAS or Manufacturers standard Every 2 years for instrument and calibrator Good practice to always use a windshield Protects from dust and knocks
Other considerations Acoustic Standards Sound Level Meters to IEC60651 and IEC60804 Newer standard is IEC61672 for SLMs Calibrators to IEC60942 (2003) Dosimeters to IEC61252
General Instrument Categories SLMs Simple SLMs (No Leq) Integrating SLMs (Leq) Octave Band SLMs for hearing protection Other applications (e.g. environmental) Dosimeters Logging or non logging
Simple SLMs Simple point and shoot Displays db level Low cost Only suitable for steady noise levels Class 2
Integrating SLMs Give Leq Level Measure simultaneous Leq and Lcpk Low cost Variable or impulsive noises Class 2 or Class 1 Lceq and Laeq for HML method
Frequency Analysis Used for selection of hearing protection Sequential or real time Caution with sequential! Also integrating (Leq) Class 1 or 2 only Other applications (e.g. environmental)
Other applications Environmental Protect microphone? Need real time analysis for frequency Different parameters and times Leq, L90, Lmax etc, 5min, 1hr intervals?
Dosimetry 2 main solutions Dosemeter Dosebadge Both solutions have advantages over each other
Dose Badge & Reader Small size Inexpensive for quantity Noise at work only No cable
Dosimeter Dual purpose (SLM or Dosi) International standards built in Download and control software Automatic report generation Comprehensive measurements I.S. Models available
Calibrators All instruments should be calibrated prior to measurement Class 1 or 2 Automatically adjusts for cavity
Conclusions Different instruments for different: Noise types Workers/Jobs Work patterns Field calibrate your unit, and have it regularly calibrated in a laboratory