What is NRR?
Noise Reduction Rating (NRR) is the measurement, in decibels (dB), of how well a hearing protector reduces noise, as specified by the Environmental Protection Agency (EPA). The higher the number, the greater the noise reduction.

What are decibels?
Intensity of sound is measured in decibels (dB). The scale runs from the faintest sound the human ear can detect, which is labeled 0 dB, to over 180 dB, the noise at a rocket pad during launch. Decibels are measured logarithmically. This means that as decibel intensity increases by units of 10, each increase is 10 times the lower figure. Thus, 20 decibels is 10 times the intensity of 10 decibels, and 30 decibels is 100 times as intense as 10 decibels.

Decibel Level

Hearing Protection Required at 85 dB or more
	0 dB	Faintest Sound Heard By Human Ear.
	30 dB	Whisper, quiet library.
	60 dB	Normal Conversation, sewing machine, typewriter.
	90 dB	Lawnmower, shop tools, forklift, truck traffic; 8 hours per day is the maximum exposure to protect 90% of people.
	100 dB	Chainsaw, pneumatic drill, snowmobile; 2 hours per day is the maximum exposure without protection.
	115 dB	Sandblasting, loud rock concert, auto horn, crying baby; 15 minutes per day is the maximum exposure without protection.
	140 dB	Gun muzzle blast, jet engine; noise causes pain and even brief exposure injures unprotected ears. Maximum allowed noise with hearing protection.
	185 dB	Rocket pad during launch, loudest animal call on earth (Blue whale). Soft tissue damage from sound waves "burning" flesh, regardless of earplugs or other hearing protection.
	194 dB	One ton of TNT exploding. Loudest possible sustained sound, varying plus or minus one atmosphere, enough to rupture eardrums.
	210+ dB	Atomic blast, meteorfall. Although it is a matter of some debate whether or not this is true sound, it can easily be lethal.

What are the laws for on-the-job exposure?
The Occupational Safety and Health Administration (OSHA), in its Hearing Conservation Amendment of 1983, requires hearing conservation programs in noisy work places. This includes a yearly hearing test for workers exposed to an average of 85 dB or more of noise during an 8-hour work day.

What does OSHA Standard 29 CFR 1910.95 require?
OSHA Action Level-85 dBA ('A'-weighted decibel)

• Monitor all noise levels
• Annual audiometric testing for exposed workers
• Annual training for exposed workers
• A variety of suitable hearing protectors must be made available at no cost to the employees

• Hearing protectors required for noise-exposed workers

OSHA Permissible Exposure Limit-90 dBA TWA

Hearing protectors required for all exposures over these levels:	Hours Per Day	8	6	4	3	2	1.5	1	0.5
	Sound Level (dBA)	90	92	95	97	100	102	105	110