Hearing Protection

The complete North hearing protection range is designed to be as comfortable as possible while protecting against hazardous noise in the workplace.


The complete North hearing protection range is designed to be as comfortable as possible while protecting against hazardous noise in the workplace.

EN standards

EN352-1 earmuffs
EN352-2 ear-plugs
EN352-3 helmet mounted earmuffs

Single Number Rating (SNR)

Determined according to International standard ISO 4869. SNR is expressed in dB’s and are used as a guide for comparing the potential noise reduction of different hearing protectors. The SNR is subtracted from overall sound level measurement to calculate the sound pressure level at the ear when wearing the hearing protector.

Noise Reduction Rating (NRR)

Noise reduction rating (NRR) is an estimate of the reduction of noise at the ear when protectors are worn properly.
While the NRR and the SNR (Single Number Rating) are designed to be used with C-weighted noise, which means that the lower frequencies are not de-emphasised, other ratings (NRR(SF) and NRSA) are determined for use with A-weighted noise levels, which have lower frequencies de-emphasised. The US National Institute for Occupational Safety and Health recommended and the U.S. EPA mandated that 7-dB compensation between C and A weighting be applied when the NRR is used with A-weighted noise levels.

OSHA has defined in their training manual for inspectors that the adequacy of hearing protection for use in a hazardous noise environment should be derated to account for how workers typically wear protection relative to how manufacturers test the protector’s attenuation in the laboratory.[14] For all types of hearing protection, OSHA’s derating factor is 50%. If used with C-weighted noise, the derated NRR will become NRR/2.[14] If used with A-weighted noise, OSHA applies the 7-dB adjustment for C-A weighting first then derates the remainder.[14] For example, a protector with 33-dB attenuation would have this derating:
Derated NRR = (33 – 7)/2

NIOSH has proposed a different method for derating based upon the type of protector.[12] For earmuffs, the NRR should be derated by 25%, for slow-recovery foam earplugs the derating is 50% for all other protection, the derating is 70%. NIOSH applies the C-A spectral compensation differently than OSHA. Where OSHA subtracts the 7-dB factor first and derates the result, NIOSH derates the NRR first and then compensates for the C-A difference. For example, to find the derated NRR for an earmuff by using the NIOSH derating system, the following equation would be used:
Derated NRR = (Original NRR x (1-.25)) – 7


A method of estimating the attenuation of hearing protectors based on 3 parameters.
H: high M: medium L: low

The terms refer to the noise reduction of the hearing protector.

Noise Source Examples

Harmful Range

• Aircraft Jet Engines

• Rivetting Hammers
• Gun Shot

• Propeller Driven
• Punch Presses
• Chainsaws

• Nail Gun
• Blasting
• Foundry Rumbling

Risk Area

• Machine Shop
• Grinding and Cutting wheels
• Pig house at feed time
• Concrete Pouring • Food Industry - Blast Chillers
• Food Industry - Homogenisers

90dB (A)
• Large Heavy Goods Vehicle
• Drilling Concrete
• Sandblasting
• Mill Worker Crushing
• Food Industry - Bottling
• Food Industry - Packaging
• Food Industry - High Boiling
• Food Industry - Bread Slicing
• Band Saws

Safe Area

• Busy Traffic
• Loud Radio
• Vacuum Cleaner

• Car Driver

• Normal Office Noise
• Conversation
• Quiet Office