ELECTRONIC EARMUFFS | ITEM 46798 |
The EPA has selected the NRR as the measure of a hearing protector’s noise reducing capabilities. Harbor Freight Tools makes no warranties as to the suitability of the NRR as a measure of actual workplace protection since such protection is highly dependent on user training, motivation, and utilization. A better estimate of workplace protection can be obtained by derating the labeled NRR by 50%.
The NRR calculated from this attenuation data is 24. Improper fit of this device will reduce its effectiveness in attenuating noise. Consult instructions for proper fit.
The level of noise entering a person’s ear, when a hearing protector is worn as directed, is closely approximated by the difference between the
ATTENUATION DATA ANSI
Test | 125 | 250 | 500 |
| 1000 | 2000 | 3150 | 4000 | 6300 | 8000 | NRR (without | Corrected |
Frequencies (Hz) |
| 40CFR211 correction) | NRR | |||||||||
|
|
|
|
|
|
|
|
|
|
|
|
|
Mean | 2.9 | 17.1 | 27.8 |
| 36.7 | 45.3 | 41.9 | 45.6 | 37.5 | 39.2 |
|
|
Attenuation (dB) |
|
|
| |||||||||
|
|
|
|
|
|
|
|
|
| 27 | 24 | |
Sandard | 2.0 | 1.4 | 1.2 |
| 3.6 | 2.6 | 1.3 | 1.8 | 2.5 | 2.1 | ||
|
|
| ||||||||||
Deviation (dB) |
|
|
| |||||||||
|
|
|
|
|
|
|
|
|
|
|
| |
Example: |
|
|
|
|
|
|
|
|
|
|
|
|
1.) The environmental noise level as measured at the ear is 92 dBA. |
| |||||||||||
2.) The NRR is 24 decibels (dB). |
|
|
|
|
|
|
|
| ||||
3.) The level of noise entering the ear is approximately equal to 68 dBA. |
| |||||||||||
For noise environments dominated by frequencies below 500 Hz, the C- weighted environmental noise level should be used.
The NRR used in the above example was achieved under laboratory conditions.
Although hearing protectors can be recommended for protection against 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.
