Mapping the way to controlling nuisance noise

Taking steps to reduce noise levels in the workplace can be expensive, but there are many benefits, both in terms of worker safety and cost reductions. However, for any mitigation activity to be appropriate and effective, an accurate assessment of noise sources is required, along with details of how noise travels around the site.

In the wide-field of chemical engineering, nuisance noise can come from a variety of sources and have a range of impacts. For example, the heat and noise generated by the distilling processes in refineries and the seemingly endless racks of pipes transporting sound across the premises can seem both deafening and disorientating. Spray-on foam is one way to help dampen the noise and reduce heat loss, but how much should be used and where will it be most effective? What other measures could be implemented to make the biggest difference?

Whether designing processes and equipment for large-scale manufacturing, test production methods and byproducts treatment, or direct facility operations, chemical engineers need to be protected from excessive noise, and plan the protection of those who will work in the situations being designed.

In the arena of noise control the saying ‘scientia potentia est’ (‘knowledge is power’) is very apt. It is not hard to recognise nuisance noise, but identifying its exact source and field of propagation can be a very different matter. If you are going to reduce noise and mitigate its harmful effects, then you need to know as much about it as possible. To be truly effective, any attempts at noise control must be based on an accurate analysis rather than guesswork or reference to previously recorded levels.

The World Health Organization, in its paper ‘Engineering Noise Control’ says: “To adequately define the noise problem and set a good basis for the control strategy, the following factors should be considered: type of noise; noise levels and temporal pattern  frequency distribution; noise sources (location, power, directivity); noise propagation pathways, through air or through structure; room acoustics (reverberation). In addition, other factors have to be considered; for example, number of exposed workers, type of work, etc.”

Getting to the source

Noise emissions on occupational sites vary widely in sound power, frequency spectra, directivity and also in their timings. Their regularity in different work situations also varies between irregularly distributed noise impulses and almost continuous noise.

The danger of hearing loss is a given if people are exposed to a noise level of more than 85 decibels (dB). The risk of hearing loss increases with the magnitude and exposure time and the frequency of the noise; with higher frequencies doing more damage. Hearing loss makes up between 30% and 40% of occupation-related illnesses.

In noisy locations, when considering how to control the sound, the primary requirement is to locate and document the areas where the noise reaches 85 dB or above. This is known as the ‘noise contour line’. In areas where noise levels exceed 85 dB, workers should wear hearing protection. Failure to clearly mark the noise contour line could leave companies open to fines and litigation. There must always be signs showing employees and visitors where hearing protection is required and it is the supervisor’s responsibility to ensure it is always worn. The contour line applies both inside the building and outside.

If a workplace has areas that may be close to or above 85 dB, then a noise study should be carried out to define all areas where hearing protection is required. Workers can also be provided with noise dosimeters to keep track of their daily dosage of noise. A well-studied and documented noise policy is better than paying for lawsuits from workers with hearing problems and paying for disability because of tinnitus and hearing loss.

Mapping the noise

Using the data from the study, and other relevant sources, with sound mapping software means that realistic noise simulations can be developed. These can show the sources of the loudest noise and the propagation across the site. Measurement alone shows only one noise level and it is not possible to assess how much noise came from any source. However, computer-devised simulations mean you can now isolate and address problem areas.

Noise mapping also means you can predict future levels of noise and take steps to control it, whereas measurements cannot occur until the entity making the noise is physically there. This means you can work with ‘what-if scenarios’ prior to building a facility and to also assess how effective new quieter equipment or noise mitigation techniques would be.

No two noise maps will be the same as their make-up is dependent on the project size, geography, objective, and most significantly, the available data which can be imported and used.

Noise reduction pays

There are a number of benefits to controlling noise in industrial situations. The protection of workers’ health should be a priority, but there are considerable financial incentives too.

Health and safety

As well as the more obvious concerns around damage to hearing, there are a number of other potential health implications of long-term exposure to excessive noise. These include sleep disturbance and cardiovascular disease as well as other physical disturbances. It can also affect workers’ psychological well-being, leading to communication issues, nervousness and reduced reactions.

Potential cost savings

Although there will be an initial outlay for noise audits, new quieter equipment and mitigation factors, properly managing noise should show a positive return on your balance sheets.

Not taking action can be expensive. If excessive noise is left untreated, businesses can face legal action from workers whose health has been affected. This in turn can increase insurance premiums. There is also the cost of lost man hours when workers take time off sick and the management time to deal with both sick leave and litigation. Those costs can soon mount up, so investing in noise control can quickly pay for itself.

Further direct cost savings can be seen with the reduction of personal protective equipment (PPE) required. Removing, or reducing the need to wear PPE can also improve working conditions and communication between workers. This can help improve productivity levels and reduce accidents.

Legal requirements

Simply ignoring nuisance noise is not an option. Most industrial nations have specific noise rules that sit alongside health and safety regulations. These include the Noise Control Act (USA), Occupational Exposure Limits (Canada), the Environmental Noise Directive (EU) and Control of Noise at Work Regulations 2005 (UK) and the Noise Pollution (Regulation and Control) Rules, 2000 (India). This national legislation requires noise control measures to be implemented so that the lowest reasonable levels of noise emission and noise exposure can be achieved. All employers should make themselves aware of the rules affecting their employees, especially if they are working across international boundaries where legislation may not be consistent.

Hearing the message loud and clear

Once you’ve created a noise map and developed your noise policy you can introduce controls to start defending workers against the problem noise. By reducing the noise by just a few decibels the risk of hearing loss and other harmful effects is considerably lessened.

Using low-noise and well-maintained equipment or placing a barrier between the worker and noise source are relatively simple steps, but they can have a huge impact on people’s lives. Using noise mapping software gives you the knowledge to accurately identify the most appropriate changes and safeguard your workers and your business.

Published in Chemical Engineering World – July 2016