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Silencers - Decibel Differences

Discussion in 'NFA Firearms and Accessories' started by JG727, Apr 19, 2011.

  1. JG727

    JG727 New Member

    Apr 12, 2011
    Tampa Bay Area, Florida
    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!
  2. Remo223

    Remo223 member

    Feb 19, 2011
    betwix the muddy mo and moon river
    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.
  3. PTK

    PTK Senior Member

    Mar 25, 2007
    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. :)
  4. Zak Smith

    Zak Smith Moderator Staff Member

    Dec 24, 2002
    Fort Collins, CO, USA.
    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
  5. JG727

    JG727 New Member

    Apr 12, 2011
    Tampa Bay Area, Florida

    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.
  6. Effigy

    Effigy Member

    Apr 15, 2011
    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.
  7. rwhankla

    rwhankla New Member

    Apr 27, 2011
    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.

  8. Rick Finsta

    Rick Finsta New Member

    May 24, 2008
    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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