Noise Reduction Ratings Explained
Noise Reduction Rating (NRR) is the measurment, in decibels, of how well a hearing protector reduces noise as specified by the Environmental Protection Agency. The higher the NRR number the greater the noise reduction. While wearing hearing protection your exposure to noise is equal to the total noise level minus the NRR of the hearing protectors in use. For example, if you were exposed to 80db of noise but were wearing earplugs with an NRR of 29, your actual noise exposure would only be 51dB.
How does wearing dual hearing protectors change NRR?
When dual protectors are used, the combined NRR provides approximately 5 - 10 decibels more than the higher rated of the two devices. For example using disposable ear plugs (NRR 29dB) with ear muffs (NRR 27dB) would provide a Noise Reduction Rating of approximately 39 decibels.
What is considered excessive noise?
The amount of on-the-job noise exposure can be determined through various testing devices. Excessive noise is defined as 85-90 decibels or more over an 8 hour period.
Examples of noise levels considered dangerous by experts are a lawnmower, a rock concert, firearms, firecrackers, headset listening systems, motorcycles, tractors, power tools and industrial machinery. All can deliver sounds in excess of 90 decibels and some up to 140 decibels.
150 dB = Rock Concerts at Peak
140 dB = Firearms, Air-Raid Siren, Jet Engine
130 dB = Jackhammer
120 dB = Jet Plane Take-off, Amplified Music at 4-6 ft., Car Stereo, Band Practice
110 dB = Machinery, Model Airplanes
100 dB = Snowmobile, Chain saw, Pneumatic Drill
90 dB = Lawnmower, Shop Tools, Truck Traffic, Subway
80 dB = Alarm Clock, Busy Street
70 dB = Vacuum Cleaner
60 dB = Conversation, Dishwasher
50 dB = Moderate Rainfall
40 dB = Quiet room
30 dB = Whisper, Quiet Library