[masraum]

Originally Posted by 908/930

I prefer to look at it as removing 30DB, so for a Miter saw that is 95DB you end up hearing the 65DB, with a gunshot of 150DB you still hear 120DB, still quite loud but way better then 150DB. I think getting above 130DB for even short durations can cause damage. I went to a Iggy Pop concert years ago it had to be up in the 130DB range, ringing in the ears for two days, LOL.

I was curious about how it works, and found the following. If it's on the Internet, it must be true. It may be; I have no idea.

https://www.coopersafety.com/earplugs-noise-reduction

When hearing protection is worn, your level of exposure to noise is based on the NRR rating of the protection device being used. Keep in mind, however, that while the NRR is measured in decibels, the hearing protector being used does not reduce the surrounding decibel level by the exact number of decibels associated with that protector’s NRR. For example, if you are at a rock concert where the level of noise exposure is 100 dB and you are wearing earplugs with an NRR 33dB, your level of exposure would not be reduced to 67 dB. Instead, to determine the actual amount of decibel deduction applied (when decibels are measured dBA which is the most common), you take the NRR number (in dB), subtract seven, and then divide by two. Given the previous example, your noise reduction equation would look like the following: (33-7)/2 = 13. This means that if you are at a rock concert with a level of noise exposure at 100 dB and you are wearing a hearing protector with an NRR 33 dB, your new level of noise exposure is 87 dB. If you are wearing a product with an NRR of 27 it would deduct 10 decibels (27-7/2=10).

When hearing protectors are worn in combination (i.e. earplugs AND earmuffs), rather than adding the two NRR numbers together, you simply add five more decibels of protection to the device with the higher NRR. For example, using 3M™ E-A-R™ Classic Earplugs (NRR 29) with 3M™ Peltor™ H7 Deluxe Earmuffs (NRR 27) would provide a Noise Reduction Rating of approximately 34 decibels.

For a better grasp of industry standards, here are a few of the most common producers of noise levels that OSHA considersto be dangerous: lawnmowers, rock concerts, firearms, firecrackers, headset listening systems, motorcycles, tractors, power tools and industrial machinery. The use of hearing protection is strongly recommended during continued exposure to any of the previously listed environments, as all can deliver sounds in excess of 90 decibels.
Painful:

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
Extremely loud:

110 dB = Machinery, Model Airplanes
100 dB = Snowmobile, Chain saw, Pneumatic Drill
90 dB = Lawnmower, Shop Tools, Truck Traffic, Subway
Very loud:

80 dB = Alarm Clock, Busy Street
70 dB = Vacuum Cleaner
60 dB = Conversation, Dishwasher
Moderate:

50 dB = Moderate Rainfall
40 dB = Quiet room
Faint:

30 dB = Whisper, Quiet Library