Thread: Suppressor sound testing

Originally Posted by stretch

Why not make using a liquid medium a "feature". If it works, it works. Are there any detrimental effects to consider?

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I don't see it being very practical and could lead to issues if someone was to put too much oil in their suppressor and it drained into the barrel.

the dB scale was a result of alexander graham bell, the inventor of the telephone. a doubling of volume was a "bell" but it was a huge measurement so it was reduced to a deci-bell. in other words a 10th of a bell.
personally i think tesla was far more of a genius and edison was somewhat a wanker

Originally Posted by berg243

would something like a felt washer glued to the baffles reduce noise or would it just reduce space thinking they could be sprayed with something like wd40 or crc and retain the liquid rather than it draining off into the lowest point of the suppressor .

Probably but that would be a rather high maintenance suppressor

How about "at shooters ear" position?

Still over the 140dB "impulse hearing safe" or whatever level...? but good to see an NZ suppressor manufacturer actually doing some testing and releasing numbers.

Any plans to use the equipment for some more focussed R&D to bring it down?

The covers you see on suppressors are to reduce the heat mirage rising off the hot suppressor, especially important if varmint shooting.

The neoprene covers of most of the usual NZ brands are more for removing the distinctive metalic " ting" noises than reducing mirage.
If shooting varmints in great numbers those covers would melt pretty quickly.
As to the advanced "tactical " covers, they do reduce the heat mirage in front of the scope but would be cooking most aluminium cans fast. They are probably more suited to steel or titanium surppressors.

Originally Posted by gimp

How about "at shooters ear" position?

Still over the 140dB "impulse hearing safe" or whatever level...? but good to see an NZ suppressor manufacturer actually doing some testing and releasing numbers.

Any plans to use the equipment for some more focussed R&D to bring it down?

Yes, and we did just that the other day, had a few different baffle designs that we tried.

Is it possible to measure the volume of the sonic crack alone ? Maybe shooting over the mic at long range? Id be interested to see what the hypothetical levels might be with complete powder burn suppression.

Originally Posted by berg243

has anyone tried extra baffles to see if different poi between more or less baffles.just asking as I have a set of 7mm baffles and wondered about adding them in for use on the range but removing them for hunting to keep my rifle nice and compact.

Adding 2-3 baffles makes no difference to my 308 bushpig poi .

To sneeze: when I stand in the but for marking targets at my local range, I prefer to ear the gentle bark of a 223 or 6 mmbr bullet than the one of a fast 30 cal or 338!
So the size of the projectile and its moving speed has definitely an influence on the noise it produces when moving through the air.

To advman: I went from 6 baffles to 10 baffles on my 17" 308 once just to test and I had no change of the poi, but i can't guaranty that on rifles with longer barrel. There is only one way to really know for sure I guess.

Originally Posted by Friwi

To sneeze: when I stand in the but for marking targets at my local range, I prefer to ear the gentle bark of a 223 or 6 mmbr bullet than the one of a fast 30 cal or 338!
So the size of the projectile and its moving speed has definitely an influence on the noise it produces when moving through the air.
.

The noise level is largely proportional to the amount of powder burned, not what's coming out the barrel. A good comparison is a .223 v .22-250. That's why I got rid of the latter.

Originally Posted by Friwi

To sneeze: when I stand in the but for marking targets at my local range, I prefer to ear the gentle bark of a 223 or 6 mmbr bullet than the one of a fast 30 cal or 338!
So the size of the projectile and its moving speed has definitely an influence on the noise it produces when moving through the air.
.

Yes it it does, in this case DPT is using a 150gr from a 308. It would be interesting to know how much of the sound is from bullet vs powder for this particular test. That would in turn show us how much sound is able to be suppressed ( noise form powder burn from a 308 shooting a 150gr) and in turn what percentage of that the suppressor is achieving.

A bit of a belated thank you to Bert at ODL for his time and use of his testing gear, and his advice and experience on the use of liquid medium in sound suppression.

Darren
Does a reduced load i.e. Trailboss bring the sound down? We just use an extra baffle currently on the 223. Very quiet.

I summarised this from an article on supressors which I found interesting. Someone will no doubt put me right if bits are wrong. It certainly helped me understand how they work.
Approximately half the energy developed by the propellent when a cartridge is fired goes to make the bullet go forward the rest is shared between recoil, gas pressure energy, gas thermal energy and gas kinetic energy.
At exit, gas pressure in the barrel is around 10_15,000 psi with a temperature of about 1000 degrees c and its travelling at supersonic speed.
The energy in the gas is divided up roughly as heat 96% pressure 3.5% and kinetic the balance so getting rid of heat and pressure are key.
As the volume doubles the pressure halves so big volume in a supressor is good, also as the temperature halves the pressure drops a corresponding amount. Baffles increase the surface area cooling the gas more quickly and also kill off kinetic energy by creating turbulence.
The ultimate aim is to have bought the propellent gas speed down below the sound barrier and to have reduced the volume as much as possible by cooling so it escapes to atmosphere quietly leaving the sonic boom of the bullets flight as the only sound