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Noise assessments

The Occupational Health and Safety Legislation require that all workplaces where it is considered that employees may be exposed to noise exceeding the exposure standard should be assessed, unless the exposure to noise can be reduced below the standard immediately. Workplaces where noise exposure is marginally below the standard should be reassessed whenever any changes, which may increase noise exposure, are made.

It is considered that when it is necessary to use a raised voice in order to communicate with a person about one metre distant, it is advisable to carry out a noise assessment.

Objectives of a Noise Assessment

The type and detail of noise assessments will depend on how the information will be used.

The general objectives of these assessments are to:

• Identify all employees likely to be exposed to noise above specified levels. This will generally involve the evaluation of LAeq,8h and measurements of peak noise levels where relevant.
• Obtaining information on noise sources and work practices that will help deciding what measures should be taken to reduce noise.
• Check the effectiveness of measures taken to reduce exposure (Provided that a base-line has been established in a more comprehensive assessment, it might be possible to restrict such surveys to measurement of noise levels at a few defined positions and under a restricted range of working or loading conditions of the equipment involved.)
• Help in the selection of appropriate personal hearing protectors.
• Delineate hearing protection areas.

The detail and accuracy needed will depend on individual circumstances encountered in the workplace.

Review of a Noise Assessment

The period between noise assessments should be determined by management in consultation with employees through established consultative processes. Assessment should be repeated at intervals not exceeding five years or whenever there is:

• Installation of new or removal of machinery.
• A change in workload or equipment operating conditions likely to cause a significant change in noise levels.
• A change in building structure likely to affect noise levels.
• Modification of working arrangements affecting the length of time employees would spend in noisy workplaces.

Undertaking the Noise Assessment

A noise assessment may be simple or quite complex, depending on the type of workplace, the number of employees and the information already available regarding noise exposure levels.

When no prior information is available, an initial noise assessment is made (walkthrough Noise Survey) to establish if noise exposure is acceptable or not.

Noise readings are to be undertaken in accordance with Australian Standards AS 1269 and AS 2659. Where readings indicate that hearing protection is likely to be necessary, readings in dB(C) may also be taken during the initial assessment in order to determine the attenuation required by personal hearing protectors. Alternatively, a separate follow-up assessment or detailed noise assessment may be required for this purpose.

In some cases, more complex measurements are required in order to determine employees’ noise exposure with acceptable accuracy, or for the selection of personal hearing protectors. For example, octave band analysis of the noise may be required if the noise contains intense tonal, high frequency or low frequency components. This can also be part of the detailed noise assessment.