The way a noise assessment is done will depend upon:
- the type of workplace
- the number of persons potentially at risk from exposure to hazardous noise
- the information already available on noise at the workplace
A noise assessment should be done during a typical working shift and should determine:
- the noise levels produced during various tasks carried out during the shift
- how long your workers are exposed to noise during each of these tasks.
An assessment should take into account:
- plant, equipment and other sources of noise in operation at the workplace
- how work activities are carried out
- the length of the shift
- environmental factors (e.g. types of walls, surfaces, the layout of workstations).
This means that adequate information about the tasks and their frequency is needed, so consultation with workers and their supervisors is essential. Noise measurements should be taken at 0.1 to 0.2 meters from the worker’s ear canal entrance over a period of time that is representative of the noise produced during the tasks.
In most situations, the use of a hand-held integrating sound level meter will produce the most useful information for choosing appropriate noise control measures. In situations where workers are highly mobile or access to the person taking the measurement is difficult or unsafe, it may be more appropriate to use personal sound exposure meters (dose meters). Noise measurements should include the combined noise levels of all the tools, machines and processes present as well as the background noise from ventilation systems, cooling compressors, circulation pumps, etc.
To identify which noise sources contribute most to workers’ exposures, the noise from each source or work activity should also be measured separately. The Ready Reckoner in Appendix C may be used to work out the total LAeq,8h for combinations of noise levels and exposure duration for each work activity and the relative importance of each.
If a group of workers is exposed to identify sources of noise and their exposure is likely to be the same, then you do not need a separate assessment for each worker. A representative assessment can be done for one or more of the workers.