Noise at Work
Published: 10th Oct 2007
The levels for action
The law has changed from the previous 1989 regulations to ensure all workers are protected against hearing damage, which is not the case with the current action levels. Approximately 14% of the working population are susceptible to hearing damage under the action levels of the 1989 regulations. Therefore the action levels are reduced by 5dB and further peak action levels introduced. The new Lower Exposure Action Value (LEAV) is 80dB for a daily dose (LAEP,d) and 135dB (LCpeak) for impulsive noises, such as pressing operations. The Upper Exposure Action Value (UEAV) is reduced to 85dB for a daily dose (LAEP,d) and 137dB for impulsive noises (LCpeak). The reduction of 5dB does not seem significant, however it will mean that an additional 1.1 million people in the UK exposed to between 80 and 85dB need to be considered.
The regulations also introduced a new concept called the ‘Exposure Limit Value’ (EPV) of 87dB LAEP,d and 140dB LCpeak. This is the maximum permitted noise level at the ear taking account of hearing protection. It may be an issue for individuals exposed to particularly high levels of noise, however it should not be seen as a minimum acceptable level, rather to highlight where action needs to be taken as a priority to reduce noise exposure. If this is the case it will be necessary to calculate the effectiveness of hearing protection by taking measurements.
The above is the case for the UK, but slight differences in the interpretation of the regulations occur in different member states across Europe. For example, the UK has defined the 8 hour dose with the nomenclature of LAEP,d, whereas in the majority of Europe it is called LEX,8h. In simple terms it is exactly the same measurement, calculation and gives the same result.
Assess and control
There is a new emphasis with the 2005 regulations, in that noise risk must be assessed and suitable controls implemented. As the title suggests it will be much more important under the Control of Noise at Work Regulations 2005 to control the risk of noise exposure. It is no longer acceptable to provide hearing protection without performing any noise exposure reduction measures.
Initially a risk assessment needs to be conducted to assess the risk to health and safety from the noise. The results will enable a program of work to be established which will isolate the actions required to reduce the noise risk.
The risk assessment itself can be simple:
- Are people exposed to noise
- Do I have machines, tools and processes that are obviously noisy
- Are control measures in place
A measurement will only be required for a risk assessment if the levels are likely to exceed 85dB. Employers still feel that measurements are important. This is due to the risk of civil claims and in order to satisfy insurers, where solid measurements that are taken can be referenced any time in the future.
Once the risk is assessed, either by a risk assessment or by measurement, controls will need to be implemented where necessary to reduce noise as low as practicably possible. Examples of these include:
- Change work patterns to reduce exposure
- Perform technical measures (dampening, enclosures etc)
- Train employees for correct use of equipment to reduce noise risk
- Maintenance of machinery
- Change the design of work areas
- Purchase quiet machinery as a company policy (‘buy quiet’)
In an ideal world the noise exposure of all employees will be reduced to below the LEAV. However, this will not be possible in many cases because the balance of costs to benefits for the above control measures will not be feasible. Hence, for employees with any residual risk from noise, hearing protection should be provided.
Health surveillance will need to be established with hearing checks for any employees over the UEAV and any susceptible employees below that. Although this may seem costly it is considered essential to ensure that the control measures are working and if effective control measures are introduced the number of employees requiring hearing protection will be reduced.
The term ‘competent person’ will not be mentioned in the new regulations. Instead, an employer can perform aspects of noise at work for which they are able. For the aspects that they are unsure of they should rely on external expert help, coining the phrase ‘expert intermediaries’ by the HSE.
If measurements are deemed necessary, a noise survey will need to be performed. A noise survey is used foremost to achieve an accurate representation of a person’s exposure to noise, either with a sound level meter or dosimeter depending on the situation.
A sound level meter is a handheld device, which enables measurements to be taken at the ear (within 10-15cm) with the instrument pointing at the noise source, measuring both ears. By repeating this exercise for all the operations that an employee performs during the day, it is then possible to calculate his or her daily exposure (LAEP,d). It is always important to inform the employee what you are doing so as not to surprise them by holding something close to the ear without their prior knowledge.
However, it may not be possible to do this in certain situations (e.g. fork lift truck drivers) or for individuals that have a complex work pattern and are therefore exposed to many different noise levels. In this situation it is best to use a noise dosimeter that is worn on the person, preferably for their entire shift. A noise dosimeter has the main body of the instrument attached to the belt, with a microphone on a cable attached to the collar near to the ear. It is important to realise that a noise dosimeter is often left unattended on an employee, which means if that person is not a responsible person, may shout into the microphone, which will overestimate the noise dose. For this reason it is best to place dosimeters on responsible employees and ignore the first few days of results so the novelty of wearing it is reduced. Many noise dosimeters are ‘logging’, which means they log the time history of the noise values. This allows you to see how the noise exposure varies through the day, allowing you to see exactly what activity the worst noise exposure is coming from. This will also instantly show, through knowledge of a person’s working day, if the instrument has been tampered with, for example, by shouting into the microphone. One advantage of the dosimeter is that if they are worn for the working shift then the noise dose will have been measured in full so no calculations will be required, except perhaps to calculate a weekly noise dose, which will be required if there is a daily variance in the noise exposure, which again will need to be assessed.
Small badge type dosimeters have been on the market for some time, where the whole product can be mounted on the shoulder near to the ear, without having a cable microphone down to an instrument on the belt. The analogue technology used in order to keep the product small has not previously been able to offer the true functionality of a dosimeter, but as digital signal processing (DSP) technology is now becoming smaller, so badge type dosimeters can offer extensive functionality as per a traditional dosimeter. An example of this is the CEL-350 dBadge which is a shoulder worn dosimeter without any cables. By being small and unobtrusive badge type dosimeters overcome any objections from employees wearing them, such that they forget they are there. This helps ensure good quality exposure data. Badge type noise dosimeters offer the ability to mount the product in a variety of different ways such as on a hard hat. This again gives the ability to keep the dBadge in an unobtrusive place.
One of the key advantages with modern noise dosimeters is in the software, which provides time saving through the generation of automatic reports, providing the required exposure information for an individual without having to copy data to other applications.
Instruments to select hearing protection
If exposed to high levels of noise, it may be necessary to calculate the effectiveness of the hearing protection provided to employees. This involves matching the frequency (Hz) of noise an employee is exposed to, with a hearing protector that provides good attenuation at those frequencies. The recommended method for doing this by the HSE is by the octave band method. This involves measuring the frequencies of noise that a person is exposed to using an octave band Sound Level Meter. A display from a typical octave band sound level meter is pictured. An ‘octave’ being a group of frequencies as represented by each bar on the display. There are different types of octave band sound level meter. Modern octave band sound level meters like the one pictured measure the octave bands in real time, that is to say they measure all of the frequencies simultaneously. This means that no intermittent noise is missed when measuring for the selection of hearing protection. Octave band analysers that use older analogue technology will measure each frequency in turn, meaning it not only takes a lot longer to measure the noise in question, but some of the intermittent noises can be missed. Therefore if the noise in question is intermittent or cyclical a real time analyser should be used. A calculator to then determine how effective the hearing protection provided can be found on the HSE website: http://www.hse.gov.uk/noise/calculator.htm. This also has noise exposure calculators, which you may find useful. Simple methods can also be used to determine the hearing protection attenuation, such as the HML or SNR method but are not as accurate as the octave band method. The full details of these three methods are described in HSE book L108 which is available from HSE books and provides very useful guidance on all aspects of implementing the regulations.
A noise survey involves much more that taking measurements. Noise exposure is as much about how long the employee is exposed to the noise as the noise level itself. Therefore, it is just as important to look and ask questions of what employees are doing and how long for, as well as their managers, in order to get an accurate idea of an employees’ exposure time. However, performing a good noise survey is as much about using your eyes and ears and knowing employees’ work patterns and responsibilities as it is about using the instrument. For example, someone whose job role it is to drill holes in metal plates may be performing that job role all day. So if you ask him or her ‘How long every day to you spend doing this job?’ you are likely to get the response ‘All day’ from the employee. Hence, if you used the noise level of when the drill is on in your exposure calculation then an incorrect dose would be calculated. What needs to be done instead is to look at the operation as a whole and analyse how long the drill spends on and off. By measuring the noise with the drill off as well as on, you will be able use both these values and times, together with their quiet times during breaks to achieve an accurate dose calculation. It is most important to remember that the LAEP,d is a personal value for each employee, not an area value. Just measuring noise at points around a site is inadequate. However, many companies like to look at ‘noise maps’ for a noisy environment. Average noise levels are taken over a ‘grid’ pattern throughout the workplace. When used in conjunction with individuals’ noise exposure, these values can give insight into where to place hearing protection zones and implement noise control. It can even be used to mark out ‘quiet corridors’ for general thoroughfares where the noise level is lower.
The HSE have come up with a very simple method for calculating overall noise dose from many different activities. This is called the Exposure Point (EP) calculator and is a way of calculating the noise dose LAEP,d in dB, without any logarithmic calculations. Again this is described in HSE book L108. This is a very useful tool unique at present to UK regulations.
Challenges for hearing protection
These new laws have also given new challenges for the selection of hearing protection and for the manufacturers of hearing protection. The first point where hearing protection becomes an issue has dropped by 5dB to an LAEP,d of 80dB, where above this employees can wear hearing protection. However, there is the problem of ‘over-attenuation’. This is where the hearing defender is too effective for the noise the individual is exposed to, and therefore sound can become muffled. This leads to a feeling of isolation, as well as the obvious danger that warning messages and sirens will go unnoticed. Therefore, if supplying to employees the same hearing protection that would have been provided under the old regulations, this problem can occur.
In order to solve this issue hearing protection manufacturers have begun to manufacture hearing protection with a lower attenuation. This gives enough protection to prevent hearing loss, but does not over attenuate. One way of doing this is to make hearing protectors that only give protection over a very limited frequency range, which some hearing protection manufacturers are looking to do in the future. With this sort of hearing defender, it will be very important to match the exact frequency the employee is exposed to, with the frequencies that the PPE will protect against. For this reason it will be important to only use octave band methods for the selection of hearing protection, where the exact frequencies of exposure are measured. The HML or SNR methods will not be sufficient.
Over one year into the 2005 Regulations, workplaces should have assessed and identified whether employees are exposed to the new noise action levels. It is very likely that many employers will have begun to implement new controls, address any high-risk individuals first and provide hearing protection for those with a residual risk. Ongoing risk assessment, monitoring, health checks and the introduction of control mechanisms should become normal working practice so that deafness and all noise related health problems can, in time, become an issue of the past.
Published: 10th Oct 2007 in Health and Safety International