Under the Australian Standard AS/NZS 1270:2002, the class system is a simple way to select a hearing protector appropriate to a noise exposure. Once the extent of the noise hazard has been determined by a noise level survey, the user simply applies this to a table like the one below to select an appropriate hearing protector.
All calculations are based on the maximum exposure limit of 85dB Leq, 8hr.
Example: If a noise level survey shows a person will be exposed to a noise level of 102dB(A)Leq8hr using the above table, we can see that a Class 4 hearing protector is required for protection against this level of noise.
In Australia the SLC80 rating is still an acceptable method for the selection of hearing protectors according to clause A2.3 in Appendix A of AS/NZS1269.3-2005.