Walker's Disrupter Guide D'utilisation page 10

Although hearing protectors can be recommended for protection against the harmful effects of
impulsive noise, the Noise Reduction Rating (NRR) is based on the attenuation of continuous noise and
may not be an accurate indicator of the protection attainable against impulsive noise such as gunfire.
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.
Example:
1. The environmental noise level as measured at the ear is 92 dBA.
2. The NRR is 22 decibels (dB)
3. The level of noise entering the ear is approximately equal to [92dB-22dB]
Caution: For noise environments dominated by frequencies below 500 Hz the C-weighted
environmental noise level should be used.
ATTENUATION DATA
Test frequencies (Hz)
Mean attenuation (dB) 32.1 27.7 31.7 31.5 38.7 41.7 40.1 42.8
Standard deviation
10
FOAM TIP NRR
125 250
4.7 3.7
500 1000 2000 3150 4000 6300 8000 NRR
4.4 2.9 3.4
TEST METHOD: ANSI S3.19-1974
43.6
4.5 4.2 3.9
CSA
CLASS
26
AL
3.5