How many supressed gunshots per day is safe?


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Arizona_Mike
June 13, 2013, 03:47 PM
OSHA Daily Permissible Noise Level Exposure is 8 hours a day at 90 db with the duration halved for every 5db increase up to 140dB. Above 140dB is considered damaging at any duration. In the range of some suppressed firearms the permitted duration gets down into the seconds.

90dB -- 8 hours
95dB -- 4 hours
100dB -- 2 hours
105dB -- 60 minutes
110dB -- 30 minutes
115dB -- 15 minutes
120dB -- 450 seconds
125dB -- 225 seconds
130dB --112 seconds
135dB -- 56 seconds
140dB -- 28 seconds

I found this example on line and it appears that 2ms would be very conservative for this gun (handgun?).
http://thesoftanonymous.files.wordpress.com/2011/10/gunshot_waveform.jpg?w=490&h=220
This source (http://www.coe.montana.edu/ee/rmaher/publications/maher_aac_0406.pdf) says 3-5ms, I'm going to go with 5ms.

Giving:
130dB -- >22,000 gunshots/day
135dB -- >11,000 gunshots/day
140dB -- >5,000 gunshots/day

Does that sound about right?

I think anyone coming even close to this exposure is having a lot more fun than I am.

Mike

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CoRoMo
June 14, 2013, 02:24 PM
When there is a lot of "structure" enclosing the shooting area (side berms, roofed/covered lanes, nearby buildings, etc.) that the sound can bounce back from, I find supersonic .223 suppressed fire to still be irritating, if not mildly painful, definitely larger bore rifle fire. But when I'm shooting out on an open area (plains, prairie) the sound isn't at all as sharp.

rcmodel
June 14, 2013, 02:34 PM
The thing is, long or repeated exposure to sounds at or above 85 decibels can cause hearing loss.

SO I'm going out on a limb here and say 22,000 gun shots at 135 DB in a day is going to do some damage to your hearing.

rc

Arizona_Mike
June 14, 2013, 05:48 PM
It sounds to me like you are going by NIOSH/CDC guidelines which start at 8 hours for 85dB and half for every 3dB instead of 5dB.

Those guidelines say driving a convertible at only 60mph with the radio off for more than 4 hours is dangerous (88dB).

I guess it depends on how safe you want to be and what you consider acceptable hearing loss. If I made a living with my ears, I'd probably want to go by NIOSH.

Anyway, doing the math, NIOSH/CDC guidelines give the following for 5ms gunshots:

120dB -- >1700 gunshots/day
125dB -->500 gunshots/day
130dB -- 175 gunshots/day
135dB -- 55 gunshots/day
140dB -- 17 gunshots/day

On a side note, NIOSH/CDC does not appear to have a max like OSHA does. The threshold for 1 gunshot being safe per day would be 152dB (again assuming 5ms).

Mike

Mot45acp
June 22, 2013, 01:57 AM
The OSHA standard is for continuous noise. I would look forthe standards for impact noise.

jmorris
June 23, 2013, 10:47 AM
Your hearing can be permanently damaged in a fraction of a second if something is loud enough.

hso
June 23, 2013, 11:30 AM
This is a CDC/NIOSH study that might be illuminating.
http://www.cdc.gov/niosh/hhe/reports/pdfs/2002-0131-2898.pdf

Regardless, subsonic ammunition through a suppressor combined with plugs and muffs results in the least opportunity for hearing damage. Is it overkill? That's dependent upon rate of fire and duration as well as the reduction in noise.

Elkins45
June 24, 2013, 08:22 PM
SO I'm going out on a limb here and say 22,000 gun shots at 135 DB in a day is going to do some damage to your hearing.

rc

Imagine the damage it would do to your bank account!

wacki
July 15, 2013, 01:05 AM
Check your limits. A lot of the graphs I've seen put a 1 second limit for 110 decibels. You have 30 minutes which is several magnitudes of order longer.

http://www.engineeringtoolbox.com/noise-exposure-level-duration-d_717.html


CDC is on the upper end of the graphs I've looked at recently and gives 90 seconds @ 110.

http://www.cdc.gov/healthyyouth/noise/signs.htm#3

Arizona_Mike
July 15, 2013, 02:02 PM
I guess it is philosophical at some point (life causes hearing loss) but by the CDC/NIOSH standard anyone who drives a convertible should be deaf.

I feel comfortable going by OSHA.

Mike

tuj
July 15, 2013, 05:55 PM
I talked to my father who is a certified safety professional and is responsible for the safety of over 10,000 employees. Here's what he had to say:

NIOSH uses slightly different criteria for measuring, which will produce higher dB readings for the same noise level (OSHA says sound pressure doubles every 5 dB, NIOSH uses a doubling rate of 3 dB). Since NIOSH is a research agency and not bound by the rule making regs, they are more up to date but also more conservative in their recommendations. Regardless, most safety professionals (including me) recommend that hearing protection be worn for any loud noise exposure, even if it is very short duration. There are a few sound meter apps that you can download for your phone, but I don’t know if they would be responsive (fast) enough to measure gunshots.

Also, noise should never exceed 140db at any time, according to OSHA

Arizona_Mike
July 15, 2013, 06:14 PM
I'm shocked at the information he gave in light of his credentials.

Sound pressure doubles every 6dB. Sound power doubles ever 3dB. There is no scientific controversy over the definitions of the dB scale.

Gunshots are beyond the dynamic range of the electric mics used in cell phones. They will be saturated whether or not they are fast enough.

Mike

jrdolall
July 15, 2013, 06:29 PM
How many artillerymen and riflemen from actual combat can hear at all? When I watch the news reels of people shooting AK-47s in the Middle East I don't notice them wearing ear protection. I'm sure there is a study online somewhere.....

As an older person who has definitely lost some hearing from shooting I just think it is a good idea to use as much ear protection as you can stand. When I was younger it was not even a consideration to use ear protection when sighting in a 30-06. I shoot a lot of suppressed .22 which is almost silent from a bolt gun using sub-sonics but I still put in my ear plugs. When shooting high power rifles I use plugs AND muffs and can still have a headache after a good day of shooting.

bainter1212
July 15, 2013, 06:41 PM
The human body is strange.....
My grandfather put a LOT of rounds towards the enemy in Korea, from multiple different rifles, and was nearly hut by artillery shells multiple times.

And yet his hearing is pretty good. Very good for 84 in fact.

Schwing
July 15, 2013, 06:49 PM
The human body is strange.....
My grandfather put a LOT of rounds towards the enemy in Korea, from multiple different rifles, and was nearly hut by artillery shells multiple times.

And yet his hearing is pretty good. Very good for 84 in fact.
I must concur with this. For me, the only reason I would use subsonic rounds is if I am shooting in a home range or if I want to otherwise keep the sound to a minimum for courtesy of those around me. I still wear ear protection personally. I know many others don't with subsonic rounds but IMHO most are still plenty loud enough to cause damage over time.

tuj
July 16, 2013, 10:17 AM
Just a little more from my father (the safety man):

According to American Rifleman, “A sound of 125db will cause ear pain and unprotected exposure at 140db or louder will result in permanent hearing loss. Most gun reports are 140db or louder. Suppressors can reduce the noise level by 20 to 30db, or even more in some cases.” That still leaves you with a noise exposure of >100 dB per shot. Anytime you experience “ringing in the ears”, the noise is too loud. Often this is a temporary condition, but if experienced regularly, can become permanent. My opinion is that hearing protection should be worn anytime someone is shooting more than a couple shots. Maybe I can bring a dosimeter to Houston sometime and we can take it to the range as an experiment.

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