- Obtain a suitable noise meter: – Class/Type 0 for laboratory tests, Class/Type 1 for lab and field work, Class/Type 2 general purpose. Get a plan of the area on which you can identify measurement positions.
- Check that the sound pressure meter batteries are okay. Always keep a spare set of batteries handy.
- Make sure that the sound meter is calibrated both before and after the noise survey to check whether there has been any change.
- Select carefully the parameters to be measured eg: A weighting, peak response, slow response etc.
- Determine the kind of sound area you are working with and find the best measuring position. Normally this will be at the operator’s working position at ear height.
- Hold the sound meter at arm’s length to avoid reflections or better still mount the sound meter on a tripod. (This is often impractical when trying to measure the noise at the hearing zone of the worker.)
- During measurement keep away from reflective surfaces and measure at a suitable distance from the machine. Make an accurate note of this position on the plan.
- Measure the background noise level (with the plant or machine turned off).
- Use a windscreen when working outdoors.
- Be careful not to accept readings if the meter is overloaded.
- Make a plan marked with measurement positions and values.
The report should include details of the type of meter used, the meter settings used, the type of sound measured (impulsive, continuous, pure tones etc) and details of the plant/equipment under observation.
6.6 NOISE AT WORK ASSESSMENTS
Note that the assessment is more than just taking a few spot measurements – it builds up a picture of exposure of individuals over a day.
The noise at work assessment:
• Assessment of the personal exposure of individuals
• Takes in to account work patterns and shift patterns
• Builds a representative picture of exposure over a typical day
• Results in a written report
• Normally repeated every two years
What to measure
- Tasks being completed
- Areas where people go to or through
- Not normally required to record levels below 75 decibels
- Measure at position of persons head
- Measure around 15cm away from head to avoid reflections
- Measure on both side of the head and record the side where the sound is loudest.
- Where there are lots of sounds and constant changes measure worst case scenario
How long to measure?
- Long enough to account for different activities
- Where noise is steady short L(A)eq
- If noise is changing all the time longer L(A)eq
- Wait for reading to settle
- Cyclic or Regular allow sound to go through number of cycles
- Nature of work (observation)
- Make sure high noise but short durations are covered
- Several workers – may be able to estimate from one worker
- Maintenance work – no typical exposure do each task
- Do not rely on just one reading
What error factors may limit the readings achieved?
- Impacts on microphone
- Wind noise
- Reflection from body
- Noise from PA systems
- General speech
- Individual’s speech – exclude
The assessment should take into account the following information:
- Observation of working practices
- Information on equipment/noise sources
- If necessary measurement of noise
- Type, level and duration of noise
- Any peak sound pressures
- Employees at risk
- Effects of any substances which may increase in a noisy environment
- Indirect effects of noise (impact with vehicles etc.)
- Availability of equipment to reduce noise
- Extension of exposure (i.e. working double shifts)
- Health surveillance findings
- References to other information
- Availability of ear defenders and attention data
Control of Noise at Work Assessment report should contain: