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Published: 14th Aug 2014

Noise induced hearing loss (NIHL) is one of the most common work related illnesses. Jane White addresses the controls that must be implemented to ensure workers’ hearing is protected.

The global burden of NIHL has a heavy price to pay, with 16 percent of cases worldwide attributed to occupational noise exposure.

At present, NIHL is thought to be incurable. It can be caused immediately by sudden, extremely loud or explosive noises, or gradually as a result of prolonged noise exposure.

Tinnitus, characterised commonly by a ringing, whistling, buzzing or humming sound in the ears, is another possible problem arising from excessive exposure to noise. This distressing condition can also lead to disturbed sleep. There is currently no treatment for noise induced tinnitus. This condition can be either temporary or permanent, but the nature of it is such that some people can experience mental health issues when trying to cope with adjusting their lives to manage the condition.

People affected by noise

Any company, within any industry or sector, can find they have unacceptable levels of noise in the workplace. Typically, it’s workers in environments with power tools, machinery or explosives, or those that operate drills, hammers, saws or engines that will be most at risk. From this list, it’s fair to deduce that workers at special risk of hearing damage are usually those in heavy production industries, such as metal working, drilling and quarrying, stone cutting, or using noisy machinery, such as in the textiles, printing, wood cutting, transportation and agriculture industries.

Any employer creating significant noise levels must do all they can to identify the hazards and assess the risks. Results from noise assessments and the information from hearing protection suppliers must be used to choose the best choice of hearing protection. They must aim to get below 85 decibels (dB) at the ear, and ensure the protection is suitable for the employees' working environment and compatible with other protective equipment, such as hard hats, dust masks and eyeprotection. From here, employers must manage those risks using controls that, ideally, remove the possibility of coming into contact with enough noise to damage hearing.

A safe volume

Regulations on noise levels vary slightly across the globe. In the UK, the 2005 Control of Noise at Work Regulations specify a lower exposure action value at a daily or weekly average noise exposure level of 80 dB. At this point the employer must provide information and training and make hearing protection available.

The upper exposure action value is set at a daily or weekly average noise exposure of 85 dB, above which the employer is required to take measures to reduce noise exposure, such as engineering controls or other technical measures. The use of hearing protection is also mandatory if the noise cannot be controlled by these measures, or while these measures are being planned or carried out.

Finally, there is an exposure limit value of 87 dB, above which no worker can be exposed - even when taking hearing protection into account.

Some manufacturing processes, or where a worker is in the proximity of an aircraft, for example, will expose the workers to peak sound pressures. In the UK, employers need to provide hearing protection on request from 135 dB, but they must do a risk assessment from 137 dB. The maximum sound pressure a worker can be exposed to is 140 dB, which is equivalent to a jet taking off.

Because noise is measured on a logarithmic scale, a reduction in noise of three decibels, which seems small, is in fact the equivalent of halving the intensity of the noise. This would mean that the person could work for twice as long at the reduced level and have the same daily personal noise exposure as before. A change of two or three decibels might not look much, but it’s important to remember that an increase of three decibels means that the sound is twice as loud. Meanwhile, an increase of 10 dB corresponds with a tenfold increase.

Eliminating risk

Before even thinking of reducing noise to lower levels it is essential that companies begin by implementing a hearing conservation programme, as this will form the foundations of any future noise reduction efforts. This is a process that involves three main parts, all of which must be effectively implemented for the system to work: health surveillance, risk assessment and noise control.

Hearing conservation should be viewed as a circular process, in which all the parts previously highlighted are interdependent. The results of audiometric testing should trigger specific assessments, which, in turn, should guide the process of control and the use of PPE. Conversely, audiometric testing should also be prompted by risk assessments, highlighting certain workers in high risk jobs.

Without getting bogged down in the details, following the practical framework outlined is the most effective way that employers can contribute to the prevention of disability due to workplace noise induced hearing damage.

A noise risk assessment will assist the employer in identifying the sources of noise, who is affected by it and what control measures are needed to reduce exposure.

To do this accurately a noise attenuation survey should be carried out. The survey will provide specific information on the total amount of noise in an environment in dB and break the noise down into specific frequency ranges or octave bands. These will indicate whether the noise consists of high, medium or base tones, or a combination thereof, and at what volumes.

It is usual to conduct a noise survey of all equipment under normal operating conditions. To do this there are many types of sound level meters available, the latest ones using digital technology and being simple to operate. They can also include a facility to record a voice tag by speaking into the microphone, so the user can record notes about the measurement location, describe what is being measured and record any other useful information.

Workers can also be provided with personal noise dosimeters to wear like badges. These measure, store and calculate the essential parameters for compliance with regulations, and can also store a time history or noise profile for that worker. These measurements can then be downloaded onto a computer and reports produced.

In terms of noise - just like any hazard that can cause damage to someone - the preferred option is always to eliminate the risk of harm. That means taking it away altogether, or reducing any chance of hearing loss from that source.

The next option is to reduce the risk, using engineering solutions to improve the situation, or limiting contact with whatever is producing the noise. Failing that, isolation is the next option, where a company might be able to screen off a noise process so that its workers cannot come into contact with it. Nearer the bottom of the hierarchy are controls using organisational procedures, such as specifying safe systems of work, training and supervision. The least preferred option is PPE. This is the final resort for limiting the risk of damage to ears, which is where hearing protection falls.

This is not to say that hearing protection does not have value. It is widely used in many sectors and businesses as an essential barrier between good health and ear damage. In addition, as technology improves, methods become more advanced and better able to protect employees, provided that the levels of behavioural health and safety are high and that staff understand and wear their protection as a matter of course.

Choosing protection

To choose the correct hearing protection you need to conduct a survey to determine how loud the noise is and how it is made up, for example, whether it is comprised of high piercing tones or low base tones. The survey results can then be used to source a solution to the problem. As mentioned earlier in this article, however, hearing protection should only be used as a last resort after other noise control methods have already been put in place, or while other protections are being developed and installed.

Companies should also ensure that the protection they provide is comfortable, so involving workers in the choice is a good way to generate wearer compliance and ensure the fit is good.

Before the PPE

As previously stated, there is a hierarchy of controls that should be explored to find the best ways to control noise. Those nearer the top of the hierarchy are always preferable and a combination of methods works best.

Employers should always try to eliminate or reduce noise first, before controlling it using operating procedures or resorting to PPE to tackle the problem. These last two options always carry with them the potential for human error, which can easily mean correct ways of working and ear defenders are forgotten.

Much of the noise generated in a factory or on a construction site can be mitigated with various techniques to lessen the damaging impact it can have on workers. At the design stage, the layout can be arranged to promote low noise emission, with noisy machinery and processes kept away from quieter areas.

Employees’ jobs can also be designed so that where they spend most of their time isn’t in close contact with noise producing equipment.

There will often be quieter processes or equipment available, as well as silencers or absorptive materials like mineral wool and open cell foam to reduce reflected sound.

Employers should ideally develop a low-noise purchasing policy, to ensure anyone responsible for buying machinery doesn’t opt for kit that produces a lot of noise. It’s good practice to implement engineering controls prior to commissioning the equipment. Mufflers can be added to heavy equipment and noise reducing saws and blades can be fitted to machinery. Equipment with metal on metal impacts and heavy vibration should always be avoided.

Continuous loud sounds can be isolated using sound barriers and enclosures to protect workers in areas such as building sites. In venues, speakers can be muffled or angled and high frequencies toned down to limit the long term effects. Often, music venues will use techniques that modify the path through which the noise reaches people - an idea other industries can adopt.

While cost is a constant issue when it comes to a company’s ability to implement a good health and safety strategy, it’s always best to take a long term view. After all, injuries and issues relating to ill health can mean expensive legal bills, poor efficiency and reduced lost time due to sick leave. Noise controls might seem expensive in the short term, but they’ll more than likely prove to be hugely cost effective.

Protection types

Hearing protection can be broadly divided into three groups: earmuffs, which cover the whole ear; canal caps, or semi inserts, which cover the entrance to the ear canal; and earplugs, which go into the ear canal.

Earplugs can be washable and reusable, or disposable, but both are suitable to protect against long term exposure to noise. They come in a variety of colours, designs and protection factors, and there are also banded earplugs, which are a cost effective and convenient option against intermittent noise during the day. These are anatomically shaped and there are no contact points, so they avoid annoying contact noise. For those workers who find earplugs uncomfortable, however, earmuffs are ideal. Whatever the chosen option, any form of ear defender will need to reduce the sound well below the relevant legal upper limit.

No employer should be attempting to provide what is only just acceptable - they should be striving to get the sound levels as comfortable and as low as they can without compromising a worker’s ability to do their job. All forms of personal hearing protection are flawed to a certain degree, as they rely on individual workers using the equipment correctly. They can also fail or be inefficient without this being visibly obvious. The effectiveness of hearing protection is reliant on its condition and whether it fits correctly. Remember, earplugs that block out too much sound increase the likelihood of a worker feeling isolated, which can lead to an unwillingness to wear ear protection.

Employers should also be aware of advancements in technology. As such, they should know that hearing protection is now able to cancel or reduce dangerous background noises, while still allowing the wearer to hear a conversation face to face. On a construction site, in a music venue, at an airport or in a manufacturing plant, these earplugs and defenders are all widely used as a way of staying aware of the working environment while staying safe from harm.

Another factor to take into consideration is the combination of PPE being used. Hard hats, dust masks or goggles, for example, might get in the way of bulkier ear defender designs, and so it takes careful planning to find the right solution. To help solve these problems, it’s ideal to involve those people who will be wearing them in the selection process. After all, if they feel the protection is impractical or uncomfortable it’s likely they’ll be removed or will remain unworn.

Consulting employees on their preferences on fit and comfort will improve the effectiveness of protective equipment, as it will be used properly.

Ensuring correct use

If hearing protection isn’t properly used it probably won’t protect employees against the noise levels they are exposed to. It’s not just training on maintenance and proper use that’s required. Behavioural safety must be woven into sessions to help people actually understand why PPE is necessary - and what can happen if they don’t use hearing protection correctly.

Without proper maintenance any protection can deteriorate or become less effective. Earplugs and other products must be kept in good condition, with seals that are undamaged and plugs that are soft, pliable and clean.

If any protectors have seals that act as a barrier between the ear and the noise they must be regularly checked for any breaks or damage. It’s also important that headbands retain their tension so drums and plugs aren’t allowed to slip.

It might be tempting for employees to modify their own pieces of equipment, but again, this might reduce the effectiveness of the protection in preventing hearing loss and tinnitus.

Employers must make it clear where it is compulsory for employees to wear hearing protection by marking out zones, using signs if possible. Training and information on how to use and maintain hearing protection must be provided. Furthermore, companies must make sure that this is being carried out in practice.

One way of ensuring hearing protection is firmly on a company’s safety radar and remains in good working condition is to include it in the safety policy, where advice and rules are set out in relation to the use and maintenance of equipment. The policy should detail who does what, when and under what circumstances, and should contain all requisite information on PPE, octave band analysis and layout drawings, as well as details such as hearing protection zones, PPE, signage, storage, procedures, information shared with employees, instructions, and training given. A good policy will have someone in charge of this area who is responsible for checking, organising replacements and repairs and reporting to chains of command on progress.

Spot checks are a useful way of seeing whether rules and procedures are being followed, as their unannounced nature means staff are more likely to abide by the policy all of the time. Anyone failing to comply should be subject to the normal disciplinary procedure.

It’s always best to lead by example, so managers and supervisors should be walking the walk, not just talking the talk, and donning their ear protection whenever it’s necessary in hearing protection zones.

As with all health and safety issues, it is important that employees are encouraged to report any problems they experience related to their hearing. This culture should be encouraged by the employer while providing appropriate support and access to health professionals.

Published: 14th Aug 2014 in Health and Safety Middle East

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Jane White