Normally the noise control program will be started using as a basis A-weighted immission
or noise exposure levels for which the standard ISO 11690-1 recommends target values and the
principles of noise control planning. A more precise way is to use immission and emission
values in frequency bands as follows.
The desired (least annoying) octave band frequency spectrum for which to aim at the
location of the exposed worker is shown in Figure 10.1 for an overall level of 90 dB(A). If the
desired level after control is 85 dB(A), then the entire curve should be displaced downwards by
5 dB. The curve is used by determining the spectrum levels (see chapter 1) in octave bands and
plotting the results on the graph to determine the required decibel reductions for each octave