Muzzle brake questions

[Hunter2011]

I once had a custom made very big over sized muzzle brake made for my PCP airgun, but very disappointingly it was not making the sound any less than the normal sized one's.
My question is that if I make a muzzle brake  that is half the size of what I currently use, how much louder will it make my 2240 as compared to my standard over the counter muzzle brake?

[Davio]

If I may put my foot in my mouth... 

In my experience constantly making many types, designs, sizes of "muzzle brakes" for our guns of various materials, I have found that at best they will disperse the sound differently but not really diminish it.  I never expected a brake to behave as an ldc... or shusher... or baffled shroud to begin with. But, I knew that it was likely that the "tone" and the perception of noise might be affected by size, bore, and venting quantity and direction.  I have found this to be true with both my own ears and with a sound meter as well.  Additionally, every testing I do of a design includes letting someone else fire the gun as I stand/listen/measure from behind, beside and frontward (although out of the direct line of fire). 

Some are more pleasing to the shooter but actually throw more of the sound directly ahead.  Since our guns are subsonic they may be termed as squirrel alerts, but then I have found even the nutters do not have reflexes any faster than the pellet hitting them.  Perhaps they do hear the shot that kills them at best.  Many more are louder to the side than straight ahead.

Our guns do not have the tip rise and dip to the extent of a powder burner.  Certainly more powerful HPA, etc. and/or bigger bores make a lie of that last statement, but with most of us playing with sub-900 fps it is true for most cases.

My conclusion: For our guns, muzzle brakes are primarily for looks.  If more or less weight is needed at the end of the barrel for balance, then that may also be a benefit.  And if a brake does happen to change the tone in a pleasant way that is an added bonus.  I have my favorites. 

[Hunter2011]

I may not use the words like sound moderators.
I don't want a muzzle brake. I want a ''muzzle brake'', if you can understand what I mean by it.
In South Africa they are 100% legal and we talk openly about them.

[onebaddj]

tko makes a very nice one. i have 3 of the 6.5 inch ones and they make it easy to shoot from my kitchen and not disturb the peoplein the living room. impact on target is louder than the actual shot. they breaks are about an inch in diameter if that.

study how muffler manufacturers make cars mufflers. it will give you ideas. 

[WyoMan]

Well said Davio 
Here's some traditional / non-traditional tips of the barrel
Muzzle brake - directs gases to the rear to offset recoil
Compensator - directs gasses upward to offset muzzle rise (flip) recoil
Flash Suppresso_r - reduces flame for better nighttime vision
Air Stripper - keeps the gases from rushing past the projectile to improve accuracy
Lead Dust Collector - for SSR cuz we not supposed to say the other word
Ornament - see "Bling"
Weight - can help balance, reduce flip and dampen vibration amplitude on the free floating barrel end
Muzzle Protector - so you don't mess up your crown
Combination - most do at least two of the above...some more

[Hunter2011]

Thanks guys. But back to my question.
Lets say you have a 8'' LDC. If you have the same one, same design, but only 4'' in length. How much more noise will there be on a co2 gun?

[onebaddj]

i dont know about the exact db loss but longer muffler has more noise disapation. but has to be more precise and aligned perfrctly. tiny bit off and all the hard work is gone in a flash.