What do firearms, jack hammers and jet engines have in common? Noise levels above 120 decibels, 140 db or more for guns.
Source: http://www.nrainstructors.org/docs/sum07-43.pdf
What Is Noise Reduction Rating
Ear protection for shooting is rated by a number, called the NRR or Noise Reduction Rating. This number corresponds to how much noise is reduced by a given piece of hearing protection and is measured in decibels (dB).
If you were exposed to 50 dB of noise while wearing 30 dB of hearing protection, for example, your ears would be exposed to about 20 dB of sound — theoretically. It’s important to remember that devices are rated under perfect conditions while being used by trained experts. In the real world, expect your protection to block out at least half of its rating in noise.
….
How Effective are Ear Plugs
Passive ear plugs don’t offer very much in the way of noise reduction. They’re a cheap and compact way of knocking a few dBs off of the levels of noise you’re exposed to, but you shouldn’t use them as your primary form of hearing protection on a regular basis.
On the other hand, they’re cheap, compact, and easily worn under ear muffs, making them a perfect secondary device for frequent or indoor shooting. It can also be a good idea to pick up an extra set of ear plugs and keep them with your shooting gear as a backup.
How Effective are Ear Muffs
Passive ear muffs are specialized devices that cover the entire outer ear. These usually feature plastic cans lined with foam that form a seal against the side of your head in order to block out noise. Passive muffs usually offer the best hearing protection at the cost of leaving you unable to hear very much of anything.
This can prevent talking with other people while you’re shooting and makes them a poor choice where communication is more important than protecting your ears. It’s important to read the documentation provided with your muffs — many models won’t offer their full NRR if there’s a lot of hair between the cup and your head, for example. Be sure to find a pair that fits comfortably and in accordance with the manufacturer’s guidelines.
Enter The Electronic Ear Muffs
Electronic noise-cancelling ear muffs use space-age technology to selectively dampen sound. These muffs are essentially passive ear muffs with holes in them in order to accommodate an electronics package that delivers quieter sounds to your ears while keeping out loud ones.
Because of the electronics, these muffs often will block much less noise than a similarly priced passive model. Don’t let that dissuade you. If you’re serious about shooting ear protection, shelling out for a top quality set of electronic noise-cancelling ear muffs will not only offer you the best protection, it’ll let you hear surrounding noise and conversation at a much less reduced level.
For the more budget conscious social shooter, consider buying a cheap set of noise-cancelling muffs to use in conjunction with in-ear plugs.
Source: http://peltortactical.org/what-every-shooter-needs-to-know-about-ear-protection/