![]() The highest-rated earmuffs I have come across have an NRR of 30 or 31. What are the highest NRR earplugs and earmuffs? Check this post for more on the relative benefits of earmuffs and earplugs. The earplugs seem to be doing better at lower frequencies, while the earmuffs seem to be better at the middle frequencies. ![]() Note that while the earmuffs and earplugs in the example above have almost the same noise reduction rating, there is a marked difference between the two at different frequencies. The NRR is then calculated from the means (using two standard deviations) in this attenuation table, assuming pink noise with a sound level of 100 dB at each frequency. ![]() The attenuation noted in the table is the mean of the individual results. Each of the 10 subjects undergoes the test 3 times so we obtain 30 different results for each frequency. ![]() The difference between the two thresholds for a given frequency is the attenuation at that frequency. In a nutshell, for each frequency, subjects listen to a pulsed test noise to determine the threshold of hearing for the uncovered ear and the threshold with the hearing protector in place. The details of the test method are specified in ANSI standard S 3.19-1974. ![]()
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