Part 5: Noise control and risk reduction

The most obvious control measure would be to remove the source of the noise. Of course this may not always be practical, in which case other measures need to be considered.

A number of standard techniques such as the provision of enclosures, fitting of silencers and the installation of barriers often represent the extent of noise control technology considered as a means of bringing about a reduction in noise levels.

Whilst in some cases, one or more of these actions may be the solution, the key question for employers is how to find out if there are alternative options that may be more practical and at a lower cost.

The difficulty is that unless a high degree of engineering expertise is available, it can be difficult to make a judgement of what constitutes the best solution in each case. However, there is a simple approach that can be followed by non-experts to determine, at least in outline, the best solution to any noise problem.

In cases where the requirement is to reduce the noise from a particular machine or process, then by adopting a systematic approach to noise control, some of the guesswork can be eliminated from determining the most practical and cost effective solutions to particular problems.

Adopting this approach is a recognition that noise is a health and safety matter, but that noise control is an engineering problem.

The procedure does not regard machines and processes as single source of noise, but as a collection of noise sources, each of which generates noise in a specific manner. The procedure must be strictly followed if the best solution is to be arrived at. It involves the following steps:

List the sources of noise

The first step is to list all of the potential noise generating sources and spilt them into the two broad categories of aerodynamic noise and mechanical noise.

Once this stage of listing and categorisation is complete, the next step is to rank the contributions from each source.

Rank the sources

The ranking of sources involves establishing the relative contribution to the total noise generated by the machine or process from each individual source. Unless this is carried out, the selection of the correct noise control measures is a matter of chance.

To achieve effective noise control it is necessary to tackle the dominant noise sources first. If the dominant sources are not tackled first, the effect of any noise control measures taken are likely to prove disappointing.

Options and costs

Once categorisation, listing and ranking of the noise sources has been carried out, you can then proceed to considering noise control techniques.

There are in fact only a limited number of plant noise control techniques available.

Noise control at source - engineering modifications that alter the process of noise generation.

Silencing - For aerodynamic sources there may be a range of conventional "silencers" available

Vibration isolation - Introduce a vibration "break" to prevent transmission of mechanical energy

Vibration Damping - Extract and dissipate the energy in vibrating surfaces

Enclosure - Prevent the transmission of sound by introducing a barrier

Barriers - Place a partial barrier between source and receiver

At this stage engineering expertise may be required in order to cost the options for each of the ranked sources and to predict the likely noise reduction for each option. The most important factor is to consider all of the options for each of the dominant noise sources.