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.
