All product packaging provides attenuation data NRR (Noise Reduction Rating).
The Following defenitions are used in the measurement of noise:
Hertz - A unit of frequency equal to 1 cycle per second.
Mean attenuation - The average data derived from all tested subjets.
Standard deviation - The difference in attenuation between the tested subjects or hor well the protection "fits" the individual.
Osha Approval Rules
1. No agency approves hearing protection.
2. Osha approves the hearing protector only in accordance to the noise level where it is used. A protector may be approved in one noise work area but not another because of the level or type (frequency) of noise present.