What is NRR (Noise Reduction Rating)?

It is an attempt to summarize a hearing protectors performance in a simple manner, by processing all the test data in accordance with an established formula. The rating is widely used and poorly understood. It gives very high weighing to the low frequency attenuation, while high frequency performance is not given the same consideration.

What is SNR (Single Number Rating)?

It is a European version of the U.S. NRR. The main difference is that the SNR is calculated using a single standard deviation, while the U.S. formula deducts two standard deviations. 

What is the HML method?

The HML method provides separate values for High, Medium and Low frequencies and provides a better estimate of actual performance. Information about the HML values for Elvex products are available on all Elvex packaging as well as in our general catalog.