To help us select hearing protection devices (HPDs) that suit our needs, there is a variety of simplified attenuation ratings that informs you of the device’s capacity to protect your ears against hazardous noises.
These hearing protector attenuation ratings vary, depending on the region. Since global companies like Howard Leight ships worldwide, packaging may indicate more than one attenuation rating.
You may be familiar with NRR or Canada Class, which are often used in North America, and if you’re curious like us, you may wonder what the other rating numbers displayed are and what they stand for.
These numbers have two things in common: they are given in decibels (dBA) and are conducted under laboratory conditions.
Let’s dive into the characteristics of the different hearing protection attenuation ratings to help you easily understand a hearing protector label.
NRR (Noise Reduction Rating)
Noise Reduction Rating (NRR) is a system mostly used in North America to determine the effectiveness of hearing protectors to reduce sound exposure. Values range from 0 to approximately 35. The higher the rating on the hearing protector label, the greater it will reduce noise exposure.
The NRR is determined by a laboratory test that is conducted by the manufacturer. These testing procedures are highly controlled, which often means that the real-world results differ.
To get a realistic value, it is recommended that the noise reduction rating be derated to better estimate your hearing device protection.
SNR (Single Number Rating)
The Single Number Rating, or SNR for short, is mainly used by the European Union. Tests are conducted at independent testing laboratories, with no involvement from manufacturers.
The SNR is conducted using a self-fitting technique. The results offer an average decibel (dBA) reduction rating based on a category of associated frequencies (low, medium, and high).
The key difference between NRR and SNR is that the latter offers a slightly higher rating.
The CSA Class method is used in Canada to rate hearing protection devices. It is a simpler classification system that categorizes hearing protection devices into classes (A, B, or C) based on attenuation levels. These attenuation levels rest on the results of the NRR laboratory tests.
- Class A: offers protection for up to 105 dBA.
- Class B: offers protection up to 95 dBA.
- Class C: offers protection up to 90 dBA.
The suffix L associated with class A or B means that the device attenuates at least 20 dBA when tested at a noise level of 125 Hz.
SLC (Sound Level Conversion)
The Sound Level of Conversion (SLC 80) is a simple rating number used in Australia and New Zealand. SLC provides users an estimate of the protection to be met or exceeded by 80% of users, based upon laboratory testing.
The SLC80 rating number indicates the decibel reduction that can be expected from a hearing protection device.