Most people having a responsibility for managing levels of noise at work will be familiar with the requirements of the Noise at Work Regulations. They should be able to quote the relevant Action Levels and the duties that have to be undertaken if they are exceeded. They are probably also aware that these Action Levels changed in April 2006 as the new Physical Agents (Noise) Directive took effect in the UK and are now known as Action Values. However, a grasp of what lies behind the Action Levels will lead to a better understanding of the regulations and improved protection of the hearing of employees.
Action Levels
First of all it is instructive to consider the origin of these Action Levels. They are based on masses of statistics of hearing loss suffered compared with noise levels that people have been exposed to. These statistics have been collected over a long period of time since Noise Induced Hearing Loss is a long-latent disease. The Action Levels are set so that the majority of people will suffer only moderate levels of hearing loss. There is no such thing as a safe level of exposure. What one would appreciate immediately from this is that even if the noise exposure of an employee is below the First Action level, there is still a risk of hearing damage.
The move to the new Directive is prompted by concerns that the current regulations present an unacceptable risk to hearing. These new limits are called Action Values and are not based on new data on hearing loss. They are merely aimed at reducing the percentage of people that are likely to be affected by Noise Induced Hearing Loss (NIHL).
Some companies spend a lot of time and effort in producing noise surveys that show exposure levels at just below Action Levels. This can be done say by reducing the time spent by employees in noisy locations. However, as we have seen above this does not mean that those employees are safe from any hearing damage.
Why hearing tests?
Having looked at the background to the Action Levels/Values, we can look briefly at the tasks facing us if these are exceeded. For those familiar with the regulations, these include the provision and use of hearing protectors, reduction of machinery noise at source and the marking out of Hearing Protection Zones. Assuming that one is putting into practise all the requirements of the current regulations, there are a number of issues that should still concern us.
• What about the hearing of staff that join the company with a pre-existing condition? As the effects of Noise Induced Hearing Loss take a long time to become a serious problem, one needs to make sure not to take on responsibility for hearing damage that may have occurred during a previous employment.
• As we have seen, the Action Levels are based on statistics, and keeping exposure below these can still result in some employees suffering hearing damage over a long term. It is important to have a way of identifying more susceptible individuals.
• Having provided hearing protectors where necessary, there is no easy way to check that these are effective, or are being worn at all. How does one make sure of this?
Hearing surveillance provides us with a way of addressing all these issues. It allows us to establish a base line for new employees. We can use this data as a benchmark to check whether this deteriorates with the current employment. It allows us to monitor all staff and identify more susceptible persons. Once highlighted, these personnel can be moved to other tasks with lower exposure levels. Finally, hearing surveillance monitors the effectiveness of the protection provided.
In recognition of this, the HSE guidance to the “Control of Noise at Work Regulations 2005” requires hearing tests for everyone who has been exposed to an Lex (formerly known as LepD) of more than 85 dB.
Different ways of testing hearing?
Many of the larger companies tend to own an Audiometer with suitably trained personnel to operate it. This is an ideal solution, albeit costly for smaller companies. There is the cost of the Audiometer to start with and associated training costs in having someone familiar with the use of it as well as being able to interpret the results.
If there is a person with suitable expertise, then rental of an Audiometer might be a cost effective way of carrying out hearing tests.
Another method is to use a mobile Audiologist. A few companies are starting to offer this bundled with other health surveillance services.
How are hearing tests carried out?
Whichever method is used, the process of checking the hearing is very similar. A range of tones at different frequencies and levels is played to the subject through a set of headphones. Whenever the subject hears a tone, they acknowledge this by pressing a button. By this means, the Audiologist determines the hearing threshold for the person. Figure 1 below shows a typical Audiogram for someone suffering from NIHL.
In addition to this basic test, the Audiologist will examine the ear canal and carry out additional tests if required. All these are usually carried out in a sound proofed booth, as some of the sound levels are quite low and general background noise may affect the results.
Picture shows an ear being examined (Otoscopy) prior to a hearing test.
The hearing threshold range will vary depending on the age and sex of the subject. If the measured hearing level is outside of this, then the contribution to this loss due to noise exposure at work has to be considered and appropriate action taken.
As all Audiometry is dependent on some feedback from the person being tested, they are susceptible to falsification. It is possible for someone to pretend that his or her hearing is worse than it is by not pressing the button, even when a tone can be clearly heard. However, professional Audiologists are trained in detecting this and have ways of double-checking results. If someone falsifies the results when a hearing checker is being used, then they would be referred to an Audiologist anyway and would then find it impossible to repeat their previous results. With any type of Audiometer, it is very difficult to falsify results to show ones hearing as being better than it really is.
Summary
In summary, hearing surveillance provides us with a number of benefits in the workplace.
• It allows us to check the hearing of new members of staff and avoid accepting any liability for hearing damage due to past employment.
• Employees who are more susceptible to NIHL can be identified and protected.
• Provide a safety net in checking that hearing protectors are being used and are proving effective.
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