Explain NRR (noise reduction rating)

K

Kirk Ethridge

New member
Looking at electronic hearing protection in the Sincalir catalog,

one pair has a NRR of 18,,, another has NRR of 24 (db)

Does the 18 lower the sound further than the 24 or vice versa?

In other words, which one of these is the "quieter" version?

Kirk
 
Noise Reduction Rating (NRR)

Noise Reduction Rating (NRR) is the measure, in decibels (dBs), of how well a hearing protector reduces noise, as specified by the Environmental Protection Agency. The higher the number, the greater the noise reduction. Anything over 85 dB can be damaging to your hearing.

Here's a sampling of noise levels:
Normal Conversation - 60dB
Auto Traffic - 75dB
Sanding - 85dB
Subway - 90dB
Woodworking - 100dB
Drilling (pneumatic) - 100dB
Power Saw - 110dB
*Gunfire - 120dB*

I recommend Electronic Earmuffs. I use Remington® R2000™ Electronic Earmuffs. These earmuffs selectively monitor sound, "shutting out anything above 84 decibels." But let normal conversation through with individual controls. They're lightweight, thin, have an adjustable headband and an "external" battery housing makes changing batteries quick and easy. Batteries are included. If you shut off the Electronics they still provide an NRR of about 23 dBs. But ALWAYS turn on the Electronics or you won't get the added benefits you're paying for. Shut them off when done or you'll find your batteries are dead the next time you go to use them. It took me awhile to remember to do that because I had always used the passive muffs. You'll find them advertised for around $100 ($99.99 at Midway) or more. I paid $54.95 at Wal-Mart. Art
 

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To help put things into perspective every 3dB is double. So 24dB is considerably more evective than 18dB. For example take the number 10 at 18dB. at 20dB that equates to 20 and at 24dB it equates to 40 and at 27dB it equates to 80 and so on. This isn't an exact calculation but for a reference it is very close.
 
The most effective have a rating of 29 Db.

If you like math, the formula is Db gain= 10*log(base 10) (sound power/reference sound power)

So is the sound power doubles, log base 10 of 2 = .3, so 10*.3= 3 db gain. If sound power goes up by a factor of 4, that would be a 6 Db gain. There is a huge difference between 18 and 24 Db.
 
another?

So, should i assume that the 24 db rated model will make the rifle shot appear quieter than an 18db rated version? Or, does the 24 model just offer protection from a "louder" noise?

I bought a peltor tactical model years ago (says 6-s on it, i guess it is a model number i'm not sure of the rating.).. I didn't really like them unless i had some ear plugs in also. One side has decided to quit working, I left em on too many times i suppose. I'm going to buy another one before too long.

Thanks for the info guys... it's been 30 yrs since i studied Bells, in my required 3 quarters of physics at UT.

Have any of you compared ratings under real life shooting? I want to buy the quietest ones

Kirk
 
Gentlemen ...

If you subtract 29 dBs from the dBs of a gun shot ... 120+ dBs ... "you've subjected your hearing to the difference ... 91 dBs." Which is above 85 dBs and harmful to your hearing. That's the trouble with "passive" earmuffs or plugs. Passive muffs only provide protection through the dampening material used in the construction of the muff itself. I've yet to see a muff or plug with an NRR rating above 31.

That's why I recommended Electronic earmuffs earlier. With Electronic muffs as soon as the dBs get to 84 dBs the electronic circuitry completely shuts off all noise a second before it becomes harmful and then returns the hearing capability a second after the harmful noise has dissipated. Through their design there is much more protection with the Electronic Earmuffs.

When you go to buy a pair of electronic muffs there is a rating given on the carton or box they are packed in. That rating is always given for the passive mode which is when they're turned off and has nothing to do with the protection provided ... 84 dBs and above ... when turned on in the Electronic mode. I hope this helps.
 
adintx,

Your correct about the way the electronics work, in that they will repoduce what they hear outside the earmuffs, and limit the output of the speakers inside the earmuffs at 84db. But, if the passive noise reduction is only 23db and a gunshot is 120db, the you will still hear the gunshot at 97db because that is what gets past the passive sound insulation even when the electronics are operating.

Basically what I a saying here is that electronic earmuffs provide no additional noise reduction above thier passive rating, even though the manufactures imply otherwise in thier advertising. The main advantage to the electronic earmuff is that it makes it easier to hear normal sounds when you have the earmuffs on.

That is why I use molded passive ear canal inserts in addition to the electronic earmuff. They can add another 15 to 20db noise reduction and get you down to safe levels.
 
David ...

David S said:
adintx,

Your correct about the way the electronics work, in that they will repoduce what they hear outside the earmuffs, and limit the output of the speakers inside the earmuffs at 84db.

But, if the passive noise reduction is only 23db and a gunshot is 120db, the you will still hear the gunshot at 97db because that is what gets past the passive sound insulation even when the electronics are operating.

Basically what I a saying here is that

electronic earmuffs provide no additional noise reduction above thier passive rating, even though the manufactures imply otherwise in thier advertising.

The main advantage to the electronic earmuff is that it makes it easier to hear normal sounds when you have the earmuffs on.

That is why I use molded passive ear canal inserts in addition to the electronic earmuff. They can add another 15 to 20db noise reduction and get you down to safe levels.
Click to expand...

Sounds like your electronics are broken or only partially working. You might want to send them back to the manufacturer for replacement. And/Or, sue for false advertising. Art
 
When I started shooting Benchrest

I realized that my hearing was the only thing on me that was still pretty much intact. I figured more was better so I always use both ear plugs and Ear muffs. Now if I had been able to do something like that to save my vision - - - - -. :mad:
 
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Davis S. has it exactly correct. Do you imagine that the electronics can mitigate the sound that makes it through the ear cups whether of not the electronics are turned on? 85 DB is the sound level (outside the muffs) that causes the electronics to attenuate the signal to the speakers. It has no relation to the amount of sound that makes it through the ear cups. Listen to a shot with the muffs turned off, and then the same shot with them turned on. The electronics are a pass through with a very quick control on the "valve”. With the "valve” closed, you hear what you would have with the same muff construction minus the electronics.

The reason for double coverage, particularly for rifle shooting from a bench, is that the higher rated muffs are too large, and will hit the stock, and the slimmer ones don't cut the sound down enough.

Also, lest you be tempted to settle for high rated plugs alone, not all of the potentially damaging sound comes through the ear canal.

Finally, a tidbit of potential prevention, I seem to remember that a military study showed that taking a daily supplement of magnesium (100 mg.) reduced the tendency to have ringing in the ears after exposure to loud noises.
 
Active Noise Reduction (ANR) electronic hearing protection can provide a greater degree of noise reduction than passive only earmuffs with the same NRR. ANR provides the greatest benefit at lower frequencies and negligible benefit at high frequencies (gunshot). That said, the technology used in most of the popular electronic muffs is NOT ANR or noise cancellation but rather different compression and filtration techniques and is designed primarily to improve close range communications in noisy environments. The vast majority of electronic ear muffs are designed to limit AMPLIFIED noise to 85 dB. As David and Boyd have said, protection from noise that exceeds 85 dB is provided by the shell and sound insulation (foam and padding) in the same manner as non electronic passive hearing protection. ANR electronic hearing protection and passive protection together may provide a negligible increase in hearing protection over passive alone in industrial applications but the benefit at the shooting range is the ability to hear range commands.


By wearing earplugs and ear muffs together the effective NRR will increase about 4 dB with a well-fitted foam earplug, and about 7 dB to a well-fitted pre-molded earplug.


Hearing loss is cumulative and permanent. Taking a pill might reduce or eliminate the ringing but will not prevent the hearing loss and the loss is still permanent.
 
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abintx said:
Sounds like your electronics are broken or only partially working. You might want to send them back to the manufacturer for replacement. And/Or, sue for false advertising. Art
Click to expand...

My earmuffs are operating just fine. It's not really false advertising because they don't come out and say that the electronics provide additional protection. They just give you the passive rating and then they say the electronics limit the output of the speakers inside the earmuffs to 85db. They don't tell you that the two ratings have nothing to do with each other and let the consumer draw whatever conclusion they want.
 
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