Under the Australian Standard AS/NZS 1270:2002, the class is an easy way to choose a hearing protector appropriate to a noise exposure. The standard rates hearing protection into five classes, with Class 1 being the lowest level of protection and Class 5 being the highest level.

The system is based on the SOUND LEVEL CONVERSION (SLC80) rating which is the difference between the sound level of the environment in which the hearing protection is worn and the sound level reaching the wearer’s ears. This is converted to a Recommended Noise Range.