If you’ve ever bought an item of PPE for hearing protection – such as ear defenders – then you may have noticed that it had an ‘SNR rating’.
But what is the SNR rating, and how does that affect the level of protection offered? Read on to find out…
The acronym ‘SNR’ stands for Single Number Rating. Measured in decibels, this is the EU standard for estimating the noise reduction offered by hearing protection products like ear plugs and ear defenders.
The SNR rating tells the buyer roughly how many decibels a sound will be reduced by when heard through that item of PPE. The higher the SNR rating, the more protection the PPE product can be said to provide to the wearer.
Hearing protection in the US is evaluated according to a different system, and given a separate Noise Reduction Rating, or NRR for short. Like the SNR, the NRR provides an indication of how many decibels a noise may be reduced by when ear defenders or ear plugs are worn.
The two ratings cannot be directly compared but, in general, SNRs tend to be a few decibels higher than NRRs.
Because noises may be high, medium or low in frequency, SNR may not always be the most appropriate tool to determine the effectiveness of an item of hearing protection.
The HML system (with HML standing for High, Medium and Low) may be used when the noise environment is most dangerous at a specific frequency level. HML values are typically found alongside the SNR or NRR on the product packaging or documentation of hearing protection devices.
Under health and safety regulations, employers have a duty to protect their employees’ hearing from excessive noise at their place of work.
In the UK, the Health and Safety Executive (HSE) recommends that hearing protection should reduce the noise level at the wearer’s ear to below 85dBA (the measure of environmental noise that takes into account the human ear’s varying sensitivity to different sound frequencies).
Therefore, choosing the right hearing protection requires an understanding of SNR (or its alternatives, depending on context), as well as knowledge of the noise levels in the working environment or caused by a specific workplace hazard. These two figures may then be used together to approximate noise levels at the ear to determine if they are within acceptable range.
The HSE has a range of useful calculator tools that may be used to do this, or you can calculate it yourself using the following method:
Workplace noise level in dB – SNR rating = Estimated noise achieved at ear
Don’t forget!
It should be remembered that the SNR of any item of hearing protection is based on ‘perfect’ conditions achieved in laboratory testing: i.e. where the item was properly fitted.
To understand the ‘real world’ performance of items of hearing protection, the HSE recommends adding an additional 4dB to the estimated noise achieved at ear to allow for factors such as poor fitting, the wearing of glasses, and interference caused by other items of PPE or headwear.
Hearing protection that reduces noise levels at the ear to below 70dB is considered over-protection, and should be avoided. This is because it may cause difficulties in communication and in hearing warning signals. Users may become isolated from their environment, leading to additional safety risks.
They may also be more tempted to remove their hearing protection, risking damage to their hearing.
When it come to buying the right hearing protection for your team, aside from noise reduction, there are several other factors you will want to consider.
Our top tips for success include:
As with all PPE, hearing protection should be kept clean, well-maintained and be stored appropriately when not in use. This will help ensure it continues to work effectively.
At iSB Group, we strive to provide our customers with the highest quality PPE for their workplace. View our full range of hearing protection products and, if you have any questions, feel free to get in touch and we will be happy to answer them.