This information is widely available on the Internet but it’s spread out across multiple websites. I’m putting this here to summarize a bunch of different information I’ve come across.
When should you protect your ears? (Based on OSHA guidelines)
Here are the limits where hearing loss begins to occur. With each increase of 3 dB the time before hearing loss occurs is cut in half.
8 hours at 85 dB
4 hours at 88 dB
2 hours at 91 dB
1 hour at 94 dB
1/2 hour at 97 dB
15 minutes at 100 dB
A rock concert is typically rated at 110+ dB. At that sound level hearing damage can begin in less than 1 minute and 45 seconds.
With the prevalence of smart phones you don’t need a specialized dB meter any more. Although, you can get one for about $30. Any smart phone can run a dB meter and most of them are accurate to within +/- 2 dB which is plenty accurate to make a decision on whether you need to use hearing protection.
I recommend the NIOSH Sound Level Meter App.
The National Institute for Occupational Safety and Health (NIOSH) is a division of the CDC and they had this app developed to their specifications. I have read far more about the multi year studies that lead to this app than any reasonable person should. It’s fully featured and completely free, no ads, or in app purchases or anything else. After all that, they only released it for iPhone.
So, I actually use this… SPL Meter
It’s fine. Just typical of what you would expect of a free app filled with ads.
This next bit is about NRR (Noise Reduction Rating) which is specific to the US. The EU uses a different rating system called SNR (Single Number Rating). Which I’m not going to get into at this time.
Hearing protection is rated with an NRR (Noise Reduction Rating) number.
This number is measured in dB (decibels).
Unfortunately, the NRR that gets listed is something only achievable in a lab.
To find the expected real world level of protection, the hearing protection industry uses this formula: (NRR -7) / 2
An NRR of 27 calculates at (27 - 7) /2 = 10 dB reduction in noise
If you combine both IN ear and OVER ear protection it is not cumulative. When combining both you only add 5 to the highest NRR.
Because of this, using OVER ear protection of NRR 25 combined with IN ear protection of NRR 30 gives a total of NRR 35 and not 55.
An NRR of 35 calculates at (35 - 7) /2 = 14 dB reduction in noise
The highest rated non-electronic OVER ear protection has an NRR of 31 dB.
3M PELTOR X5A Over-the-Head Ear Muffs, Noise Protection, NRR 31 dB
The highest rated non-electronic IN ear protection has an NRR of 33 dB.
3M E-A-Rsoft Yellow Neons, NRR 33 dB
If you come across a product claiming a higher NRR than these, they are either using the EU SNR numbering system or you will need to read very carefully to figure out what the real story is. According to everything I’ve read the only way to get better protection than what I’ve listed above is to move to using electronic noise canceling devices.
Alright, that’s all I’ve got. Please chime in with what you’ve tried, what you liked, what you hated, or whatever your experiences have been.