Sound advice on controlling noise

It has been almost a decade since the ‘Control of Noise at Work Act 2005’ was passed. Shortly after it became law in April 2006, the HSE released figures that estimated there were around 17,000 people in the UK on record as suffering problems resulting from excessive noise at work, including ringing in the ears, deafness or some other form of hearing loss. The importance of greater control of noise at work was clear to see.

Noise is essentially unwanted sound and exposure to excessive noise can have a variety of effects, including: psychic reactions such as irritation or anger, which arise from a sustained sound level as low as 35 decibels (dBa); vegetative reactions such as nervousness, stress and interrupted concentration, arising from sound levels from 65dBa; hearing impairment including incurable damage to the inner ear, occurring from 80dBa upwards; and mechanical damage and complete deafness, occurring from sound levels from 120dBa upwards.

Measuring noise levels

The main method for measuring compressor air system noise is the enveloping surface method of DIN 45635 or other norms such as Cagi-Pneurop and PN 8 NTC 2.3. These standards define the conditions for measuring the noise that air compressors emit to the outside air (noise output) according to standard industry methods. This means that the results are comparable.

Identifying the source

Once high noise level emissions have been detected, the next step for maintenance teams is to identify the source of the noise. Unsurprisingly perhaps, there are a wide range of possible sources where high levels of noise can emit from, including the motor, air-end, after-cooler, leaking pipes, fittings, and in the case of an oil-injected compressed air system, the air/oil separator. By carrying out a risk assessment a decision can then be made on what action is required and a strategy for reducing high noise level emissions can be developed.

Controlling noise

Following the identification of noise sources, maintenance teams must consider a variety of options that can reduce any impact noise has on workers. Best practice dictates the use of appropriate personal protective equipment (PPE) such as ear plugs or defenders, however there are other methods available that can reduce the volume of noise in an environment. Relying on PPE alone is not an option, because it should be a last resort and not a solution.

One option is for companies to move compressors to a room or area away from workers. This is a common practice that is employed in many factories, however it can sometimes be expensive. An alternative to this option is some form of engineering control, such as noise abatement, where acoustic enclosures or sound barriers are used as a solution for reducing compressed air system noise output. 

The design of the compressor itself can also help to reduce noise. The latest compressed air systems use advanced technology to minimise noise emissions from moving parts. Recent developments to the speed, size and mechanical characteristics of the air-end of a compressor, combined with the power and of variable speed controls can all play a crucial in both improving operational efficiency and reducing noise emissions.

As the figures released by the HSE almost a decade ago highlight, significantly more workers than many would expect were previously suffering from problems resulting from excessive noise exposure. Since the introduction of the ‘Control of Noise at Work Act 2005’ the likelihood is that workers are better protected, but this will only be the case by if noise is effectively measured and controlled.