* Trusted Since 1992 Test according to ANSI Specs S3.19-1974 The level of noise entering a person"s ear, when hearing protector is worn as directed, is closely approximated by the difference between the A-weighted environmental noise level and the NRR. Attenuation Chart (ANSI S3.19-1974) Frequency 125 250 500 1000 2000 3150 4000 6300 8000 Mean Attenuation (dB) 38.4 40.3 43.2 41.8 38.6 45.0 45.7 49.6 47.3 Standard Deviation (dB) 2.9 3.5 4.0 3.8 2.6 2.8 3.5 3.8 4.3 Example: 1. The environmental noise level as measured at the ear is 92 decibels dB(A). 2. The NRR is 32 decibels (dB). 3. The level of the noise entering the ear is approximately 60 dB(A). Noise Reduction Rating 32 Decibels (When Used As Directed). The range of noise reduction ratings for existing hearing protectors is approximately 0 to 30 (Higher numbers denote greater effectiveness).