Silencers - Decibel Differences


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JG727
April 19, 2011, 12:24 PM
Every one talks about the decibel differences between suppressors, or between suppressed firearms and non-suppressed firearms.

Now, I've only been around suppressed .22lr pistols, so I am VERY far from an expert.

The question I have is this:
Someone in another thread commented how their suppressor lowered their pistol to 115-125 dB's. I know that decibels are base 10 logarithmic, so that the drop from 140 or more dB's to 115 is a LOT, but is it enough to shoot comfortably without hearing protection?

I start classes to be a gunsmith this fall, and suppressors are really interesting to me, but I don't have a whole lot of hands on experience, and what i do have is with small bore stuff.

Thanks for your patience with my questions!
Jim

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Remo223
April 19, 2011, 12:41 PM
Its a log scale for a good reason. Just like earthquakes, the energy released increases faster than the perceived intensity increases.

Therefore, a dB difference converted to a non log base ten difference, would not be representative of the perceived sound loudness difference.

Also, there is a different loudness perceived with different pitches. Lower pitched sounds can have a much higher dB level than higher pitched sounds yet still seem to be less loud. It takes much more energy to generate lower pitched sounds than it does higher pitched sounds

If you ever played a wind or brass instrument in a band, you should remember that your lungs must move much more air to generate the lower notes than the higher notes.

PTK
April 19, 2011, 01:43 PM
Generally, yes, 115dB is quiet enough for shooting sans earplugs when talking about firearms. The intensity is indeed 115dB, but the peak energy is only there for a fraction of a second. If it was 115dB sustained, it would cause hearing loss.

Feel free to ask other questions, I have experience with silencers on just about everything. :)

Zak Smith
April 19, 2011, 02:13 PM
A couple other notes

* "Mil spec" sound tests are one 1 meter to either side of the muzzle, not at the ear

* Sound test results can vary quite a bit from source to source. It's best to test things side by side.

* Halving the sound pressure decreases the dB level by 3 dB. Doubling it increases by 3 dB. Doubling the distance from the source is a 6 dB change.

Here are some old threads that are relevant
http://www.thehighroad.org/showthread.php?t=252786
http://www.thehighroad.org/showthread.php?t=250828&highlight=hearing+damage

JG727
April 20, 2011, 09:20 AM
Thank you!
Those links are very informative!
Turns out I was properly protecting my hearing, but now I'm tempted to get a pair of those custom ear plugs.
Jim

Effigy
April 21, 2011, 12:31 AM
85dB is the established danger zone for hearing loss, at least for sustained noise. If the suppressed gun is registering 115dB I'd still wear hearing protection. It depends on whether you're shooting inside or outdoors as well. Shooting in a wide open space, you'd run less risk if you skipped the hearing protection.

rwhankla
May 5, 2011, 11:06 PM
I'm just a college student, but I work with my father during the summers assisting with industrial audiology. 85 dB is for a sustained 8 hour work day. It would depend on how many rounds you fire at 115 dB AND how much more noise you would encounter in that same 8 hour period (mowing the grass etc.) as to how long you could go without hearing loss. I believe the time of exposure splits in half for every 3 dB you increase. Meaning the intensity doubles exponentially.

85 dB = 8 hours
88 dB = 4 hours
91 dB = 2 hours
94 dB = 1 hour
97 dB = 30 mins
100 dB = 15 mins
103 dB = 7.5 mins
106 dB = 3.75mins
109 dB = 1.875 mins
112 dB = .9375 mins
115 db = .46875 mins (30 seconds...ish)

Another thing to keep in mind - When shooting a rifle, your "offhand" ear (Left ear if you shoot righthanded) is turned slightly closer to the end of the rifle/shotgun (to an extent with handguns also), whereas your "shooting" ear is turned away and muffled by your shoulder. If you do get a silencer, measure how loud it is at your "offhand" ear as it will receive significantly more noise.

These are NIOSH/CDC standards which are safer. OSHA I believe increases in 5 dB increments.

Ryan

Rick Finsta
May 12, 2011, 02:30 PM
140dB is the cutoff for instantaneous exposure hearing damage. The sonic crack of the bullet is usually around 136-140dB depending on altitude, humidity, temperature, etc., so the suppressor really can only bring you to the edge of "hearing safe" with a supersonic round.

That said, I find my .30cal bolt gun comfortable to shoot sans earpro in open spaces (no side berms to reflect noise), but my AR-15 is certainly not.

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