Workers in the United Kingdom are protected by the Control of Noise at Work Regulations 2005: a set laws designed to prevent noise-induced hearing loss in the workplace.
The regulations set out what employers and employees need to do to reduce harmful noise to a minimum.
In practice, there isn't a single all-encompassing noise limit in the regulations, rather there are a series of different thresholds which either must not be exceeded or require action if they are exceeded. These are termed the "exposure limit values" and "exposure action values". Employers need to carry out risk assessments to determine the noise levels that workers are exposed to and compare them against these thresholds.
Before getting into the limits themselves, it's important to note that the regulations use two different ways of expressing noise exposure. These are the daily or weekly personal noise exposure level and the peak noise exposure level.
Daily (or weekly) Personal Noise Exposure
The personal noise exposure is a calculation of the cumulative noise exposure of an individual over the course of an 8-hour day, denoted using the LEP,d descriptor. The LEP,d calculation automatically corrects for the amount of time that the person is exposed to the noise, so if the employee works for more or less than 8 hours in a day then this will be reflected in a higher or lower personal noise exposure level accordingly.
The regulations also allow the personal noise exposure level to be calculated over an average week (LEP,w) instead of a day. This is used only when the type of work undertaken varies markedly from day to day.
Peak Noise Exposure
The peak noise exposure refers to the instantaneous noise level rather than an average or cumulative noise exposure over a shift. The peak level is considered to be exceeded if the noise level exceeds the specified value at any time, no matter about the duration. This is most relevant to those that work around transient sounds such as the noise from a nail gun.
Understanding the basic difference between Daily / Weekly Personal Noise Exposure Level and Peak Noise Exposure means you can properly interpret the "noise limits" in the regulations.
A brief note on 'dBA' and 'dBC'...
All the noises around us are made up of many different frequencies of sound. The daily personal noise exposure level is measured using what's known as an A-Weighting filter (dBA). This is simply a correction automatically applied by the sound meter to reflect the normal human hearing response across different sound frequencies. The Peak Noise Exposure is measured using a slightly different filter - the C-Weighting (dBC).
It's not necessary to have a deep understanding of these frequency weightings as long as the sound level meter you are using is set up to measure the correct ones.
The noise limits - what are they?
Exposure Limit Values (ELVs)
The simplest set of limits in the regulations are the exposure limit values which are the closest thing in the regulations to a 'noise limit' in the literal sense. The exposure limit values are:
a daily (or weekly) personal noise exposure level of 87 dB (a-weighted).
a peak noise exposure of 140 dB (c-weighted).
When determining whether these Exposure Limit Values have been exceeded, you are allowed to account for the sound reduction of any ear protectors being worn - as long as the employee does actually wear them!
In our experience, it is unusual for the peak noise exposure part of the exposure limit values to be exceeded unless there are exceptionally loud noises in the workplace. It is more likely that the daily or weekly personal noise exposure level limit would be exceeded.
Exposure Action Values (EAVs)
The exposure action values (EAVs) are sometimes referred to as limits, but in reality they are called "action values" and not "limits" for a reason. The exposure action values are levels which, if exceeded, place requirements on the employer and/or employee to take action.
There are two sets of exposure action values.
Lower Exposure Action Values
a daily (or weekly) personal noise exposure level of 80 dB (a-weighted).
a peak noise exposure of 135 dB (c-weighted).
Upper Exposure Action Values
a daily (or weekly) personal noise exposure level of 85 dB (a-weighted).
a peak noise exposure of 137 dB (c-weighted).
These EAVs are expressed using the personal noise exposure and peak noise exposure parameters as the exposure limit values, but that's where the similarities end.
It's very important to note that the effect of any hearing protection on offer should be ignored when determining whether a Lower or Upper Exposure Action Value has been exceeded; a key difference between the Exposure Action Values and Exposure Limit Values.
There are a series of requirements (actions) which need to be put in place if the risk assessment determines that the noise exposure of employees is at or above the Lower or Upper EAVs. These do include providing hearing protection for those whose personal noise exposure is at or above the Lower EAV and enforcing the use of hearing protection if workers noise exposure is at or above the Upper EAV.
Of course, hearing protection isn't the end of the story. In fact, it's not even the starting point...
The regulations include a number of other control measures that might need to be put in place depending on the noise exposure of employees.
Other control measures include providing information and training on noise risks, reducing the noise at source using quieter equipment or methods, and undertaking health surveillance (hearing testing). Stay tuned for more blog posts where we will delve into these aspects of the regulations.
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