sound mitigation @ outdoor range

[twofifty]

A current thread on hearing loss caused by firing indoors in a SD situation has me thinking of ways to improve shooter comfort on the firing line.

At my club's outdoor range, the firing line is protected by an overhead roof, sheeted with corrugated metal screwed over plywood. This roof, 10' to 12' above our heads, reflects quite a lot of sound energy back to the shooters. There are no walls.

Do you guys think this reflected sound energy could be reduced by fastening wooden slats (say 1x4 spruce) to the underside of the roof? Thinking of spacing this 'false ceiling' maybe 6" lower than the roof, to give the gun blasts a space in which to dissipate and bounce around?

Opinions?
Other ideas?

Thanks.

 

[PT1911]

flat surfaces direct sound right back at you every time... the key is angles angles angles... For example...If one were to section off the ceiling with pyramid shaped sections , the sound would be deflected in all directions rather than directly back down... also, shooting lanes angled outward... IE, narrowest at the shooting station and widest at the target, will allow the sound waves to deflect away from you rather than echoing between parallel burms.

 

[MikeNice]

Put a flat plywood roof on the top. Create a two inch space and fill it with polyfill. Then drop down about six inches and put in your "dropped ceiling." Add a difuser to dropped ceiling and coat it in some roll on or spray on sound deading material. You can also use "duct board" but that gets expensive pretty quick.

Edit to add:
If you want to go with the simple drop ceiling put a sheet of sound deadening material on the bottom side of the bottom panel. Something like Vblok VB2. It is a soft dampener that will slow down the sound wave and reduce reflection. By slowing down and reducing the sound wave you can minimize the peak SPL. If you put the VB2 between the spruce slats, on the bottom of the cielling, it will help a little bit more.

 

[racine]

Purchase the best soft ear plugs you can get along with the muffs with the highest noise reduction possible. Bulky ones may give you 29-30+ db of protection to which the plugs add another 5 db as audiologists will tell you. I've shot indoors quite a bit and this combo is very effective. It makes communication hard but that's the tradeoff. FWIW, I shoot indoors only in very inclement weather like winter in Denver.

 

[whipper]

PT1911 has the answer, by using pyramid shapes it will redirect the sound. A cheap pyramid shape is egg crate flats. My buddy used them to line his garage with for band practice; you can feel the beet and it sound like they are miles away sitting right outside of the garage. This is good because he needs all the practice he can get!
Just my 2 cents.

 

[hso]

Gotta agree with PT1911, deflect the noise away from the shooting station with a steeply angled panel.

Also, consider absorbing as MikeNice has suggested, but remember that all manner of critters will try to live in the sound absorbing materials.

 

[Sock Puppet]

Perforated metal sheets are another material commonly used in sound attenuation, but the cost may be prohibitive for such a large area.

 

[MikeNice]

Yeah if you use the polyfill you will have to seal and caulk the seams. You could use Duct Board instead. It will cut down on the noise and is a little more enviromentally tolerant. It is usually used in HVAC installs so it holds up well to extremes in cold and heat. Plus, it is more tolerant of condensation.

Put it on the top side of the dropped ceiling between the slats. It works very well. I have seen it used in the walls of professional studios in Nashville and Atlanta.

Combine that with a steep angle and you should see an improvement. Do all of that and use the Vblok and you will see a big difference.

Another thing that might help is 2 or 3 inches of mulch on the ground. The irregular shapes and edges of the mulch acts as a diffuser. It will diffuse the sound as it passes through towards the earth. It then diffuses it again as it is reflected. It also has some absorbtive (is that a word) characteristics. If you have hard clay or rocky soil it can help. It can make picking up brass a pain in that rear though.

 

[twofifty]

Thanks for all the suggestions.

I like the low-cost aspects of breaking up the reflective surfaces with eggcrates and mulch, and will suggest these to my club. Aesthetics are not our first concern.