When noise levels are particularly high, it is important to assess the performance of the hearing protectors that are being used. Three methods are available for calculating the sound level at the ear. This page covers the more accurate Octave Band Method. The other methods are HML and NRR.
You also need the Assumed Protection Values or APV for each hearing protector. This is the expected attenuation that the protector offers in each of the octave bands. If the APV is not provided then it is equal to the Mean Attenuation - Standard Deviation in each band.
In the example above, the hearing protector's APV values have been entered along with the sound level measured in each octave band.
The following results are shown:
|Calculated Level||This is the estimated level at the ear.|
|Graph||The graph shows the measured noise level in red and the calculated level at the ear in green. This simple graph can by handy for spotting tonal problems.|
Over Protection and Under Protection: You should usually aim to reduce the noise level at the ear to between 70 and 80 dB. If you reduce it below 70 dB then there is a good chance that you are over-protecting, making it difficult to hear speech and warning sounders. The worker is also less likely to wear such protection at all times.