baffles in silencers

[Dixticat]

Hello, I am coming from a french forum (http://patator.frbb.net) and I have a question which you could answer better.
I am making a silencer for my 8mm pneumatic canon (I put from 100 to 450 psi of air in it) :




I have ceramic wool to insulate the sound but I want to add baffle (maybe 3 or 4), and I have no idea how to put them : in some design like in this picture :



the spacing beetween the baffles increase toward the end of the silencer, and in some case that's the opposite...
I've seen also baffles that have an equal separation, baffles with holes (that is supposed to work better), and silencer like this : who have a long, a short, then a long chamber.

So what should I do ? I don't want to do something experimental but just a design that showed its ability.

Thank you.

[Lentamentalisk]

Well one way that has proven to work is you make them closer spaced towards the end of the silencer. The idea is that the gas expands into the large baffle area, lowering the pressure and inertia, and then it gets caught up in all of the baffles, slowing its release.

I am not going to say that that is the only, or the best way to do it, as nobody has truly figured that out, but it has been proven to work quite well.
It seems as though the "best" method would use some sort of frequency matching, to cancel out the sound waves, but I have no clue how to go about that.

[Dixticat]

Thx for your advice, but I don't think I have all the hi-tech tool and accuracy for a wave cancelling system, and according to wikipedia it's not proven that it could work...

[metalmeltr]

For what reason are you incorporating a silencer into the gun?

[Lentamentalisk]

Um... I am just going to make a wild guess, and say that he is trying to make the gun quieter... Just a guess though.

[metalmeltr]

I understand to make the gun quiter, but why do you want a quieter gun, you also lose energy that could continue forcing the ammo from the barrel insted of directing it into the silencer.

[Lentamentalisk]

Um... No. First off, a quieter gun makes the neighbors less mad. It also means you don't need hearing protection to use it without damaging your ears. It also might make it possible to use indoors. A silencer reduces recoil as well. Not to mention, they look really cool.
This silencer he is making is a screw on one, meaning that it attaches to the end of the barrel, making the gun longer, rather than bleeding off gas from the barrel, keeping it the same length. He will lose no performance what so ever, and it may even become more accurate, as there will be less muzzle blast.

[metalmeltr]

How loud can an air cannon be? My 1/2" barrel 200psi ball valve cannon is rather quiet and I can not imaging higher pressure being terribly loud.

[Dixticat]

It's not that loud in my case, but enough to affect my neighbourhood.
When the pressure goes up, the sound is more "sharp" and can be more identified as a gun, in my opinion. I just make a silencer to be quieter.

[POLAND_SPUD]

My 1/2" barrel 200psi ball valve

that's becasue ball valve cannons are quieter than piston guns

[c11man]

come try to shoot my 700psi bearing cannon without ear protection

[metalmeltr]

I shoot shotguns and use all kinds of power tools without hearing protection, just how loud is this thing?

[c11man]

its very very lound for the shooter because of placement of the qev vent, about 2inches from the ear, it is pointing away but it still hurts

[metalmeltr]

have pictures of this gun been posted?

[c11man]

not realy, but its uses a qev as the pilot and that rests on your shoulder for a stock, there is a elbow to redirect the air away from you though