Employers’ maintenance of a safe working environment depends to a great extent on relevant decision-makers understanding what workplace sound levels are and how to measure them.
Investing in a reliable decibel meter (also known as a sound level meter) can certainly be one important step for organisations in the UK seeking to adhere to their legal responsibility to assess and control noise exposure.
However, there are certain other things that employers must know if they are to be successful in their first steps towards managing occupational noise.
What Is Meant by The Term ‘Workplace Sound Levels’?
Sound is produced by pressure variations travelling through a medium, such as air. A sound level measurement, normally expressed in decibels (dB), gives an indication of the magnitude of these pressures.
It might be presumed by some casual observers that the “level” of workplace noise would simply be determined by whether a particular sound seems objectively “loud”.
However, this would be a dangerous presumption for a number of reasons. Firstly, as the UK Health and Safety Executive (HSE) highlights, noise exposure does not need to feel painfully loud to cause harm over time.
Secondly, it is crucial to understand that sound intensity is measured on a logarithmic rather than linear scale, with every increase of 3 dB roughly doubling the sound energy. This means even relatively small rises in sound levels can significantly heighten the risk to workers at a given site.
How Long Employees Are Exposed to Noise Is Another Crucial Factor
Even an individual sound-level reading doesn’t show the full picture, as the length of time for which employees are exposed to noise will also need to be considered.
One given worker may be exposed to a moderately high level for a significant proportion of their working day. A colleague of theirs, meanwhile, might be subjected to much higher levels for shorter periods.
UK Legal Thresholds for Workplace Sound Levels
The Control of Noise at Work Regulations 2005 set out clear exposure action values and limit values. These are based on daily and weekly personal noise exposure (LEP,d or LEP,w) and peak sound pressure:
- Lower exposure action values: 80 dB(A) daily/weekly average and 135 dB(C) peak. At these levels, employers are required to assess the risk, provide information and training, and make hearing protection available on request.
- Upper exposure action values: 85 dB(A) daily/weekly average and 137 dB(C) peak. These are the levels at which hearing protection becomes mandatory, it is essential for hearing protection zones to be marked, and employers must put in place a programme of noise control measures so far as is reasonably practicable.
- Exposure limit values: 87 dB(A) daily/weekly average and 140 dB(C) peak. Employers must not allow employees’ noise exposure to exceed these levels. The limit values also differ from the action values in that they take account of the attenuation provided by any hearing protection worn.
If, for example, workers have to raise their voices to be heard at about two metres, they experience muffled hearing after a shift, or they make regular use of noisy power tools, these are simple indicators of a formal assessment potentially being needed.
How Are Sound Levels Measured in The Workplace?
As touched on earlier in this guide, it is decibels, or dB, in which sound pressure levels are typically expressed. Two frequency weightings play a central role in workplace noise level assessments:
- A-weighting, or dB(A), approximates the human ear’s response at moderate levels. It is used for continuous or fluctuating noise exposure over a working day or week. The key metric is the equivalent continuous A-weighted level (LAeq). From this, daily personal noise exposure (LEP,d or LEX,8h) is calculated by combining level and duration.
- C-weighting, or dB(C), is used for peak (impulse or impact) measurements (LCpeak). This is due to it responding more evenly across frequencies and capturing short, high-energy events that can bring about immediate damage.
It is crucial for any noise measurements taken to be representative of actual worker exposure. With a view to ensuring this, approaches may encompass the likes of task-based sampling (measuring typical tasks and weight by time spent), job-based sampling, and/or full-shift monitoring.
Conclusion: It’s Not Just About One-Off Noise Readings
Ultimately, if employers are to properly understand the topic of workplace sound levels, they will need to look beyond the single numbers recorded on meters.
The overall risk to their employees can be impacted by a variety of factors, such as the particular level of noise, its frequency characteristics, the speed with which it changes, and how long employees are exposed to it.
Accounting for all these elements can put employers in a stronger position to understand workplace sound levels, as well as take the steps necessary to assess and control the risk wherever their employees do their jobs.
