When we are exposed to noise over a period of time, we risk damaging our hearing if the levels are high. As a result, in order to protect our hearing, many countries have introduced noise exposure limits at work which must not be exceeded.

For steady noise, good correlation has been demonstrated between hearing damage risk and A-weighted sound level measurements although the duration of exposure must also be considered.

This Noise Dose is a way of showing how much noise exposure a person has received in relation to this limit. It is often measured using at least a type II noise meter or alternatively by wearing a noise dose meter during the course of a working day.

The noise level (LAeq) of any particular machine or working position is measured in dB (or alternatively the Leq is expressed in dB(A)) but this is only the start of the assessment. The LAep,d is what is required for by the legislation and this is a calculated parameter based on the noise level plus the exposure time of a worker to that noise level.

The Laws / Standards

The control of noise at work regulations NI (2006) dictates the noise action levels & limit values.  EEC Directive EEC/86/188 - The protection of workers from the risk related to the exposure to noise at work is the umbrella EU directive, with complementary International Standards ISO 9612 - Guidelines for the measurement and assessment of exposure to noise in a working environment & ISO 1999 - Determination of occupational noise exposure and estimation of noise-induced hearing Impairment.


What Are The Action Levels And Limit Values?

The Noise Regulations require you to take specific action at certain action values. These relate to: the levels of exposure to noise of your employees averaged over a working day or week; and the maximum noise (peak sound pressure) to which employees are exposed in a working day.

Lower exposure action values:

  • daily or weekly exposure of 80 dB;
  • peak sound pressure of 135 dB;

Upper exposure action values:

  • daily or weekly exposure of 85 dB;
  • peak sound pressure of 137 dB.

Exposure limit values (not to be exceeded):

  • daily or weekly exposure of 87 dB;
  • peak sound pressure of 140 dB.


Workplace Noise Assessments: