Sound advice

Whether a new dam or hydroelectricity power plant is being constructed or an existing power station is being expanded, it is important to assess and mitigate the impact of noise. This is particularly important at the planning and preliminary design stages, when noise control strategies should be implemented. Too often, facilities are developed without properly assessing the noise likely to be generated and how to reduce it. Mitigating noise (and other potentially harmful emissions) doesn’t have to be a case of trial and error, or result in expensive retrofits.

Noise during the construction phase is unavoidable, but it can minimised. In addition, steps to reduce noise once the plant is up and running, from hydro turbines, generator cooling systems and hydro turbine casings should also be taken. This will not only help to prevent annoying residents in the nearby vicinity, but will also protect people working on the site.

Why is noise such an issue?

Industrial noise can cause both temporary and permanent hearing damage. Hearing loss comes from exposure to noise over time where it may occur gradually, or a sudden, exceptionally loud noise can trigger it instantly.

As significant as it is, it is easy to assume that hearing loss is the only issue caused by exposure to high levels of noise, but there are a number of other potential impacts. These include sleep disturbance, cardiovascular disease, fatigue and other physical disturbances. Recent investigations suggest a link between noise and dementia, as well as potentially cancer and diabetes in women.

Mental health can also be affected by exposure to excessive noise. Psychological conditions include communication disturbance, reduced or delayed reactions and the reduction of psychological wellbeing (which could manifest itself in increased nervousness, frustration or aggression).

Knowledge is power

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.

Noise emissions from dam construction and hydroelectricity can 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.

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.

Getting to the source

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.

When considering how to control 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 to? 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 and noise mitigation 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.

Alongside the physical and emotional issues associated with hearing loss, there is also a financial impact both for the individual and businesses through loss of earnings, through lost working days, litigation, recruitment costs and reputational damage. 

Mapping the noise

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, using sound mapping mean you can now isolate and address problem areas.

Using the data from a noise study, and other relevant sources, sound mapping software enables realistic noise simulations to be developed. These can show the sources of the loudest noise and the propagation across the site.

With sound-mapping software you are able to produce a map of the power plant building or landscape in question, and produce a visual display of how the noise will travel and at what volumes it will be.

Noise mapping also means you can predict future levels of noise and take steps to control it, whereas measurements cannot be taken 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.

The multiple visualization options in a sound map mean that hydroelectricity plants which often have extensive and complex results data can be viewed from different aspects. This helps the user identify the problem areas and recognize the noise reduction potential.

When choosing which sound-mapping software is best for you there are a number of factors to consider:

1. Open source – Will you be able to transfer your data to a new software system should you need to? If it’s produced in proprietary software, you’ll be locked into using that system or have to start again from scratch if you want to move.
2. Good resolution – Is the map that’s created a high-resolution image? Can you make out small details to help with noise mitigation planning or does it just give an overview of the situation?
3. Displays information – Does it contain the information or just present a picture? To be fully effective the information should be displayed within the map and different views should be available.
4. Information manipulation – Are data files all merged or are they separate for easy manipulation and extraction?
5. Meeting your requirements – Depending on the size of project, the software solution may change. For a small project a tailored version may be sufficient, but if the project grows will the software be able to cope and will a more complete version be compatible?
6. Ease of use – Can you get it to do what you need it to do easily? Be careful though, if it seems very easy to use straightaway it may be because the software is basic and won’t be able to handle all of your requirements.
7. Ongoing support – Will you get help to use the software after you’ve purchased it and how easy is it to upgrade it?

Noise reduction pays

Although there will be an initial outlay for noise audits, new quieter equipment and other 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 or local residents 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. 

While important to health and safety, providing the necessary PPE such as ear plugs and ear muffs is not cheap, and the administration costs of maintaining sufficient supplies can mount up too. By reducing the noise at source, the requirement for PPE can be dramatically reduced.

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 Pollution (Regulation and Control) Rules, 2000 (India), Noise Control Act (USA), Occupational Exposure Limits (Canada), the Environmental Noise Directive (EU) and Control of Noise at Work Regulations 2005 (UK). 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, local residents and your business.

Arne Berndt is owner/adviser at SoundPLAN International

www.soundplan.com