Thread: Suppressor sound testing

Hi All,

We have started to do a few suppressor sound tests this week with the proper sound equipment (B&K 2209 with 4136 mic) using a factory Rem 700 308 sps, 24” with factory Winchester 150gr power point.

Our standard over barrel suppressor with four baffles gives an average sound reduction of 21.92db Additional baffles give 1 to 2db sound reduction each, we tested up to 9 baffles that gave us an average reduction of 31.20db

One of the test we thought would be fun was to try something we read in the book by Al Paulson: Suppressors ,history and performances volume one, on how to rig a suppressor test by using a liquid medium inside the suppressor to absorb some of the energy of the shot. (this reduced the first shot by nearly 8db more than a dry suppressor)

Video bellow.

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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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.

Robbie Tiffen told me years ago that you could reduce the decibels by spraying CRC inside a suppressor but I never tried it.

Interesting. I wonder what effect if any it would have on accuracy.

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Originally Posted by R93

Robbie Tiffen told me years ago that you could reduce the decibels by spraying CRC inside a suppressor but I never tried it.

Interesting. I wonder what effect if any it would have on accuracy.

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grabbed one these today to throw in the range bag . . . certainly small enough to carry up the hill if it works . . cheers for the idea

Would be interesting to see what other energy absorbing media can achieve - eg a silicon strip or washer on the face of each baffle, or even a suppressor design that was packed like a motorcycle muffler with fibrous material.

@DPT I thought the suppressor would have more reduction of db than that. It sure seems like it when using one. Why a 24" barrel?? not many people would be using a barrel this long. Great to see you doing the sound test

Originally Posted by bigbear

@DPT I thought the suppressor would have more reduction of db than that. It sure seems like it when using one. Why a 24" barrel?? not many people would be using a barrel this long. Great to see you doing the sound test

@bigbear

every 3dB reduction is a halving of the sound energy.

Every 10dB reduction a ten fold reduction in sound intensity.

So a 21dB reduction via the DPT supressor is quite a significant reduction

Cheers
Pete

Originally Posted by bigbear

@DPT I thought the suppressor would have more reduction of db than that. It sure seems like it when using one. Why a 24" barrel?? not many people would be using a barrel this long. Great to see you doing the sound test

That's what we had available in 308.
db figures are meaningless to most people as 20db what does that really mean? every 9db reduction in sound is perceived half the volume, so if you go from 100db to 109db it will sound twice as loud. Every time you double the energy you gain 3db, the 308 we shot un suppressed is 167.9db, if we were to get another 308 and shoot them side by side at the same time, the volume would only go up by 3db, you would need four 308s side by side to sound twice as loud as just one.

DPT

The Decibel scale is not linear its logarithmic so 101 db is 10 times louder than 100db if my maths is right. So the unsupressed rifle is 130% louder. A pretty impressive sound reduction.

Originally Posted by Marty Henry

The Decibel scale is not linear its logarithmic so 101 db is 10 times louder than 100db if my maths is right. So the unsupressed rifle is 130% louder. A pretty impressive sound reduction.

And Sound level reduces by -6bB every time the distance doubles, so reduction at point of firing pays dividends at distance.

The first shot is loudest because of the oxygen in the suppressor, subsequent shots are quieter because the gas from the previous shot has displaced the oxygen. Similarly oil, CRC etc. achieves a similar result except the subsequent shots are quieter because of the firing gases mixed with oil fumes/smoke. That effect wears off after 4-5 shots and you get back to the normal repeat shot level. Sound absorbing materials, packing etc. reduce the effectiveness of any suppressor by reducing the volume needed to trap the gases. The most efficient units are filled with inert gas and sealed with thin plastic baffles. Such things are used by special forces but are only effective for the first couple of shots, and are not practical for normal use. 30 decibels of suppression is about the practical limit, and most suppressors are in the low to mid 20's which is fine for normal use, giving effective ear protection and confusing game.

Originally Posted by gundoc

The first shot is loudest because of the oxygen in the suppressor, subsequent shots are quieter because the gas from the previous shot has displaced the oxygen. Similarly oil, CRC etc. achieves a similar result except the subsequent shots are quieter because of the firing gases mixed with oil fumes/smoke. That effect wears off after 4-5 shots and you get back to the normal repeat shot level. Sound absorbing materials, packing etc. reduce the effectiveness of any suppressor by reducing the volume needed to trap the gases. The most efficient units are filled with inert gas and sealed with thin plastic baffles. Such things are used by special forces but are only effective for the first couple of shots, and are not practical for normal use. 30 decibels of suppression is about the practical limit, and most suppressors are in the low to mid 20's which is fine for normal use, giving effective ear protection and confusing game.

So if you sprayed a heap of argon say into your suppressor before firing you would have a better result?

Originally Posted by Nibblet

So if you sprayed a heap of argon say into your suppressor before firing you would have a better result?

Absolutely!

I think covers are just to reduce noise if the can brushes against scrub. They would have a negative effect on the ability of the supressor to radiate heat, and as thats one way the sound is reduced would make the less effective after a couple of shots.