Occupational Noise Assessments

Occupational Safety and Health Consultants Register – British Occupational Hygiene Society (BOHS)

It is essential that you can show that your estimate of employees’ exposure is representative of the work that they do. It needs to take account of:

• the work they do or are likely to do;
• the ways in which they do the work; and
• how it might vary from one day to the next.

Your estimate must be based on reliable information, eg measurements in your own workplace, information from other workplaces similar to yours, or data from suppliers of machinery.

Hand-held sound-level meters

One method is the use of a hand-held sound-level meter. This is most suited to making sample noise measurements at the position of a person’s head.  Where the measurement is made at the side of a person’s head, it should be made on the side where noise levels are higher. Where a person is working in an area with a broader diffuse noise source then the measuring position is not so critical, as it is the noise level in the area into which the person is entering that is being measured. In this case taking an average noise measurement over the area may be appropriate.

Personal dosemeters

Another method is the use of dosemeters. These have the advantage of being able to measure noise over prolonged periods of time, even the full working day. Various types are in use but all of them will have a microphone that can be mounted on the shoulder, to make a representative measurement of noise at the
head position. The microphone should be placed on the side of the head most exposed to noise. Elevated noise levels will be recorded where dosemeters are mistreated. They can be prone to errors by accidentally knocking, rubbing or covering the microphone, so employers need to be sure that the levels recorded
reflect the working conditions. They often allow a visual record of noise levels over time to be produced, so can help to understand the dominant sources of noise exposure for people who are exposed to various noise sources during the day.

Fixed monitoring

This is often used by employers to monitor noise levels in a specific area where previous investigations have established a level that should not be exceeded. A microphone will be installed at a point that has been identified as being important for monitoring and the information relayed to a metering point that can be seen by a supervisor. This is useful in clubs and pubs where bands bring in their own equipment.

The aim of the risk assessment is to help you decide what you need to do to ensure the health and safety of your employees who are exposed to noise. It is more than just taking measurements of noise – sometimes measurements may not even be necessary.

Your risk assessment should:

• Identify where there may be a risk from noise and who is likely to be affected;
• Contain a reliable estimate of your employees’ exposures, and compare the exposure with the exposure action values and limit values;
• Identify what you need to do to comply with the law, eg whether noise-control measures or hearing protection are needed, and, if so, where and what type; and
• Identify any employees who need to be provided with health surveillance and whether any are at particular risk.