mufs over plugs NRR rating confussed

[rufunky]

I'm a little confussed

Acording to the quote below by moderator hso, if I get earplugs rated at NRR 33 coupled with my NRR 22 mufs this should give me 38 NRR.

If I had got mufs with a NRR 35 coupled with earplugs rated at NRR 33 would I have had more or the same amount of protection??


http://www.thehighroad.org/showthread.php?t=220715
------------------------------------------------------------------------------------------------------------------------------------
If a pair of muffs have an NRR of 33 and the noise you're exposed to is 140 dB then the muffs soak up 33 dB of the 140 dB. This leaves 110 dB to get through to your ears. Add plugs to the muffs and you get anohter 5 dB protection added to the higher of the two. NRR 30 plugs + NRR 20 muffs = NRR 35 combined. NRR 30 plugs + NRR 30 muffs still equals NRR 35 due to the different frequencies the muffs and plugs absorb.
------------------------------------------------------------------------------------------------------------------------------------

 

[bigfatdave]

NRR = Noise Reduction Rating
It isn't additive, each layer can only add a fraction of the value you would get with that layer alone.

And exact values aren't as important as the principle of "if you feel any pain or hear any ringing after shooting, you're not using enough". Generally the plugs will have the greatest effect, I wouldn't bother with muffs alone because my glasses and long-gun stocks tend to pop the seal on muffs at the worst moments, thus muffs are mostly for other people's loudenboomers that I can't control.

Get what works, get better stuff as you figure out what styles you like best ... if in the end you end up with plugs, muffs, and a noise-isolating booth ... so be it.

 

[CHEVELLE427]

MY 15 YEAR OLD daughter has to were the foam ones with the muff type and can still here me talking 50 feet away, talk about hearing but only when she wants to.

 

[jhansman]

Numbers, schmumbers. If I (or anyone I am next to) am shooting anything other than rimfire, it's plugs and muffs. I almost invariably end up next to some guy shooting a .308 with a muzzle brake.

 

[rufunky]

Thanks for the responses.

buttt, I'd still like to have an answer to my original question out of curiosity

 

[DRYHUMOR]

This may help

http://www.osha.gov/dts/osta/otm/noise/hcp/attenuation_estimation.html

From the osha site:

For dual protection (ear muffs and plugs are used simultaneously) use the following:

1. Determine the laboratory-based NRR for the higher rated protector (NRRh).

2. Subtract 7 dB from NRRh if using A-weighted sound level data.

3. Add 5 dB to the field-adjusted NRR to account for the use of the second hearing protector.

4. Subtract the remainder from the TWA as follows:

Estimated Exposure (dBA) = TWA (dBC) - (NRRh + 5) , or

Estimated Exposure (dBA) = TWA (dBA) - [(NRRh- 7) + 5]

Example:

TWA=110 dBA, plug NRR=29, and muff NRR=25 dB

Estimated Exposure = 110 - [(29 - 7) + 5] = 83 dBA


Though it does get confusing.

Best thing is to get dual protection with the highest NNR you can find.

Keep in mind if you wear glasses, the muffs' NRR is reduced a bit, as the sealing surface is broken by the ear piece.

Tinnitus sucks, ask me how I know.........