Everything you need to know about Single Number Rating (SNR)

Single Number Rating (SNR) helps measure how effectively hearing protection reduces noise exposure.

It provides one clear value that allows workers and employers to compare the noise-reducing capability of different ear defenders and ear plugs. 

Noise-induced hearing loss remains one of the most common workplace health issues. Choosing hearing protection with the right SNR rating is an important part of controlling exposure and meeting legal responsibilities. 

This guide explains how SNR works, how it’s tested, and how to select hearing protection that suits different workplace environments.

What SNR means in hearing protection

SNR stands for Single Number Rating.

It represents the average amount of noise reduction a hearing protection product can provide when worn correctly.

The number shows how many decibels (dB) of noise are reduced at the ear. This makes it easier to compare ear plugs, earmuffs, and helmet-mounted ear defenders across brands and models.

How SNR is tested

SNR values are determined through controlled laboratory testing.

These tests measure noise attenuation across a range of frequencies, including both low and high-pitched sounds, to calculate an average performance level.

The SNR shown on product packaging reflects this standardised testing method. Actual noise reduction in the workplace may be lower due to fit, wear time, and how the product is used.

LEGAL NOISE LIMITS IN THE WORKPLACE

In the UK, employers must assess and control noise exposure at work.

The legal noise exposure values are:

• Lower exposure action value: 80 dB(A)
• Upper exposure action value: 85 dB(A)
• Exposure limit value: 87 dB(A), taking hearing protection into account

Where exposure reaches or exceeds these levels, employers must introduce control measures. Hearing protection is used where risks cannot be adequately reduced by other means.

Choosing hearing protection by SNR level

Hearing protection should be selected based on workplace noise readings and the aim of reducing exposure to a safe level.

Higher SNR values provide greater noise reduction, but protection must be matched to the environment. Over-protection can isolate workers and make communication or alarm recognition difficult. Under-protection may leave workers exposed to harmful noise.

Fit and comfort are just as important as SNR. Poorly fitted or uncomfortable protection is less likely to be worn correctly, reducing its effectiveness.

Workers should also be trained on how to fit and wear hearing protection properly to achieve the expected level of noise reduction.

SMI’s range of hearing protection includes options suitable for low-medium and high-noise environments.

Common SNR values in workplace PPE

Ear plugs, earmuffs, and helmet-mounted hearing protectors are available in a range of SNR values.

Typical SNR ratings include:

• 20 dB
• 25 dB
• 30 dB
• 33 dB

These values help users choose suitable protection for construction, manufacturing, logistics, engineering, and other noise-intensive environments.

Products such as helmet-mounted ear defenders support teams working around machinery, while high-attenuation ear plugs benefit workers exposed to long periods of sustained noise.

FAQs

Can hearing protection be customised?

Some ear defenders and helmet-mounted systems can support branding or integrate with other PPE. 

For workplaces needing specific configurations, SMI’s team can advise on suitable hearing protection products.

What’s the difference between SNR and NRR?

SNR is the European noise-reduction rating system. NRR is used primarily in the United States.

Both measure noise attenuation, but they use different testing methods. Values are not directly interchangeable.

SNR is the standard used for hearing protection across the UK and Europe.

How can I calculate effective noise reduction?

A simple estimate can be made by subtracting the SNR rating from the measured workplace noise level.

This provides an approximate exposure level at the ear when the product is worn correctly. Actual protection depends on fit, condition, and correct use.

Does a higher SNR always mean better protection?

Not always. The aim is to reduce noise exposure to a safe level without over-protecting the wearer.

Excessive attenuation can reduce awareness and communication, so SNR should always be matched to the task and environment.