The Single Number Rating (SNR) and Noise Reduction Rating (NRR) determines the degree of noise cancellation the ear defenders or earplug provides. When choosing ear defenders, it is important to note its SNR/NRR and ensure that after deduction the noise passing through the ear defenders is below 85dB. This is to ensure that prolonged exposure to the noise with ear defenders on will not damage the user’s hearing.
In areas where noise levels are very high, ear defenders and ear plugs can be worn together to give better protection. However the increase in SNR/NRR is not the addition of both ear defenders and ear plug SNR/NRR value. Instead, the additional protection provided is about 5 – 10 SNR/NRR higher than the better of both SNR/NRR individual values. This ear defenders and ear plugs combination is better described by the diagram below.
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