http://www.dangerousdecibels.org/education/information-center/decibel-exposure-time-guidelines/
Posted on 10/31/2014 4:41:50 AM PDT by LouAvul
I asked an audiologist yesterday, but she didn't know.
I always thought the NRR on a pack of ear plugs meant that was how much they reduced the noise.
Then I read that to determine the true noise reducing effect, one subtracts seven from the NRR and divides by two.
That means if my plugs have a NRR of 27-7/2=10. So if I'm firing a weapon = 169dB and only wearing earplugs, the noise hitting my ears is 159dB. That's still well above the instant damage level. Even wearing muffs, you only add 5dB to the protection which still equates to instant damage.
Is this accurate, because if it is, it's no wonder so many shooters have to yell at each other.
Oh, and the audiologist determined that I have mild hearing damage in my left ear and mild to moderate in my right. Dunno exactly what to blame. Loud music. Construction equipment. Bird hunting.
WHAT??
Rear Plugs or re ear plugs.
Noise Reduction Rating (NRR) is a unit of measurement used to determine the effectiveness of hearing protection devices to decrease sound exposure within a given working environment. Classified by their potential to reduce noise in decibels (dB), a term used to categorize the power or density of sound, hearing protectors must be tested and approved by the American National Standards (ANSI) in accordance with the Occupational Safety & Health Administration (OSHA). The higher the NRR number associated with a hearing protector, the greater the potential for noise reduction.
How does NRR change decibels of exposure?
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).
*To maximize noise reduction, hearing protectors must be worn properly.
More at link
http://www.dangerousdecibels.org/education/information-center/decibel-exposure-time-guidelines/
You also need to understand sound pressure level (SPL).
You might want to post this later in the day. People old enough to have suffered hearing loss might not be up yet. Personally, I would wear both plugs and muffs. It is tiring to go through life constantly having to ask people to repeat themselves.
I’ve found that military issue earplugs are by far the best.
Good argument for suppressors. I prefer muffs as they seem to be more effective. Did a lot of shooting in my youth w/o protection and, other than the ringing, my hearing tests OK
Equivalent sound level contours. Octave band sound pressure levels may be converted to the equivalent A-weighted sound level by plotting them on this graph and noting the A-weighted sound level corresponding to the point of highest penetration into the sound level contours. This equivalent A-weighted sound level, which may differ from the actual A-weighted sound level of the noise, is used to determine exposure limits from Table 1.G-16.
1910.95(b)(1)
When employees are subjected to sound exceeding those listed in Table G-16, feasible administrative or engineering controls shall be utilized. If such controls fail to reduce sound levels within the levels of Table G-16, personal protective equipment shall be provided and used to reduce sound levels within the levels of the table.
1910.95(b)(2)
If the variations in noise level involve maxima at intervals of 1 second or less, it is to be considered continuous.
TABLE G-16 - PERMISSIBLE NOISE EXPOSURES (1)
______________________________________________________________
|
Duration per day, hours | Sound level dBA slow response
____________________________|_________________________________
|
8...........................| 90
6...........................| 92
4...........................| 95
3...........................| 97
2...........................| 100
1 1/2 ......................| 102
1...........................| 105
1/2 ........................| 110
1/4 or less................| 115
____________________________|________________________________
https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=standards&p_id=9735
It does has its advantages in married life...
The problem with standard meters is that they are not capable of measuring low frequency noise/sounds and they are not calibrated well most of the time to begin with. In this case I would not trust OSHA on this.
Being a bass player and reading the warnings on my amps or in their respective manuals, plus hearing the sound and feeling the pressure personally, I would be willing to bet that sound pressure production at the sub 1KHz range vs. that graph is way off. In fact more than a few sources I’ve read claim exactly that.
I’ll see if I can find some references.
I don’t think it’s accurate. I use ear plugs every day. I’d be stone deaf if your equation were true. Shooting, however, is a tough case because of the huge (how ever transient) pressure levels. I’d wear plugs and muffs.
I would welcome better sources.
Working as a design engineer, OSHA is the law I have to follow. It doesn’t mean I cannot do better in designs, but it is the minimum legal requirement.
Are you kidding?
The older we get, the less sleep we need (besides, we're looking for batteries for our hearing aids).
It's the kids who would sleep until lunch, if you let 'em.
It works better if you just don’t care what they are saying.
Wore ear plugs and ear protection where I onced worked, a good set of ear muffs provide better protection because it covers the whole ear.
Ear plugs only block out some noise, not all.
https://www.noisemeters.com/help/faq/frequency-weighting.asp
A-weighting assumes how the human ear works in relation to frequency and dB. Real SPL at low frequency is not dependent on how the human ear works WRT decibels and frequency to cause damage. If the SPL is very high at very low frequencies such as 10-60Hz, then most dB meters (let alone SPL meters) will not represent the true SPL. Even dB meters with C-Weighting will miss the mark below roughly 100Hz because they are not linear in that region.
In my experience most dB meters and SPL meters along with OSHA/other regulatory bodies’ recommendations miss the mark when it comes to low frequency dB and SPL measurements.
I know there are more sources out there that back up my claims, but I’m busy with other stuff now.
Maybe I’ll look more later.
Where does Hillary’s screeching come on the scale?
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