Typical noise levels
Noise is measured in decibels (dB). There are two aspects to sound measurements:
- the frequency of the sound
- the intensity of the sound.
The decibel scale is logarithmic: a small increase in the decibel level is, in reality, a big increase in the noise level. For example, an increase of only 3dB doubles the noise level at the human ear and halves the time a person should be exposed to it once harmful levels are reached.
GreenFacts provides more information on aspects of sound and how it’s measured.
Hazardous noise levels
It is difficult to specify what level of noise is absolutely safe, as individuals are affected by noise differently. However, noise levels above 7580 dB(A) are known to cause hearing damage. The louder the noise is, the less time it takes to cause damage. For example, noise levels at 85 dB(A) may take as long as eight hours to cause hearing damage, while noise at 100 dB(A) may start damaging hair cells in the ear after only 30 minutes.
To establish whether a hazardous level of noise exists within the workplace, employers need to check whether a normal conversation at a distance of about one metre can be carried out. If there is difficulty in communicating then it is likely that noise levels are high.
The following table shows the World Health Organization’s recommended noise levels in various occupations:
The following table shows ILO’s recommended exposure limits of noise levels per day: