Casella explores Noise-Induced Hearing Loss (NIHL) and the different methods of monitoring the noise exposure of your workforce.

Noise Induced Hearing Loss: How can you start monitoring the exposure of your workforce?


In the UK, an estimated 14,000 people working during the reporting period suffered from noise induced hearing loss (NIHL), new as well as longstanding cases, caused or made worse by work.[¹] In the USA, 16% of noise-exposued tested workers have a material hearing impairment.[²]

The cause of NIHL is preventable but the affects are permanent, resulting in life changing injuries that can seriously impair a workers’ quality of life. Industries with the highest incidences of NIHL include manufacturing, construction, energy and mining. Prolonged exposure to dangerous levels of noise in the workplace is concerning and could lead to serious health issues whilst preventing workers from operating at their best.

Noise monitoring provides concrete data, highlighting key avenues for change. Statistics could significantly improve if people within organisations had the knowledge and understanding of noise measurements and terminology. Upskilling your own workforce could help you start seeing instant improvements in workplace noise levels and employee exposure.


Why monitor?


The Control of Noise at Workplacenoise regulations are in place in countries around the world to protect workers to ensure workers’ hearing is protected from excessive noise exposure. The level at which employers must provide hearing protection varies between country but is often 85 decibels.

To ensure employers adhere to these regulations, monitoring provides accurate insights into noise levels and identifying where the problem areas are. If you are keen to train up your own workforce, there are many devices on the market but it can be difficult to identify what type of product is most suitable for your working environment and where training is required.  


What to monitor?  


When monitoring noise levels, both ‘action’ and ‘exposure’ levels should be measured. Action levels in noise monitoring exist in two forms. Firstly, measurements must be taken based on a workers’ average exposure over a working day. This protects employees from damage to hearing over the span of their working lives. Secondly, instantaneous damage can occur to hearing from high levels of impulsive noise. Damage caused from this type of exposure can result in a ‘ringing’ sound in the ears. If there is a risk of this type of exposure, then peak noise levels should also be monitored and recorded.


Measuring noise exposure doesn’t have to take a lot of time, or cost the business a lot of money through the use of external resources.   A successful noise monitoring programme can be carried out by on-site, trained health and safety managers, using either a sound level meter or a dosimeter.


How to monitor: Sound level meters


A sound level meter is a hand-held device, enabling measurements to be taken at the ear (within 10-15cm) with the instrument pointing at the noise source. This process must be repeated for both ears, for all duties employees perform, making it possible to calculate an accurate record of daily exposure. Settings on these meters can be adjusted, according to the type of noise being assessed. Monitors should be compatible to the international IEC 61672 Class 2 standard ensuring correct measurements are made.


When using a sound level meter, measurements must be started at the beginning of a task, representing workers’ actual exposure.  If workers are likely to be exposed to high levels of impulsive noise, emitted from heavy pressing operations or sheet metal working, peak noises must be measured for accurate results and compared to peak action levels. The operator is present when measuring the noise so generally, good quality measurements are gathered.



If individual working patterns are complex, or if the work is carried out means it is not practical or safe to conduct noise monitoring with a sound level meter, dosimeters can be used. These are small, shoulder worn devices that will collect individual exposure data.


How to monitor: Dosimeters


Dosimeters are worn by employees for their entire working shift.  Data is instantly logged and when downloaded onto another device, it details the time history of the noise exposure, highlighting where high exposures occur throughout the day. Workers can also make a diary of times and jobs performed, allowing the employer to instantly see the operations that require more effective noise controls.


 It is important to remember that noise dosimeter measurements are open to spurious results from employees, especially when first used. Employees could try and shout into it, or press buttons. So, high exposures should be checked to see if they are a legitimate part of the workers exposure. Modern noise dosimeters can also record the actual audio. This would allow the sound to be played back to determine what the exposure was from a particular machine, or indeed that it was spurious. Ensuring regulations are met, employers must purchase dosimeters that are compliant with the IEC 61252 standard. 


Noise Survey


If you want to conduct a complete noise survey, this involves much more than simply taking measurements with either a sound level meter or noise dosimeter. Whilst looking at noise levels, how long the employee is actually exposed to the noise level must also be considered.


Teaching those conducting noise surveys to ask questions to employees and managers throughout the process  is key in gaining a total understanding of what employees are doing and how long they are doing it for, leading to accurate concepts of exposure level and times.  The importance of using their own instinct and eyes and ears to understand working patterns and responsibilities without just relying on the instruments is also vital.


Someone whose job role may be to drill holes into metal plates might not be actually doing that all day and you need to consider this. If they were to ask them how long they spent doing the job, the likely response will be “all day”, which is not the case.  How long the drill is turned on and off and how long the operation takes must also be analysed.


The future


The figures of workers affected by NIHL is concerning and employers have a crucial responsibility to protect workers’ health from being damaged.  Upskilling your own workforce could be the way to achieve government standards and protect your workforce, constantly ensuring noise levels are at an appropriate level.