The silencer issue
by B.B. Pelletier
Curtis asked a number of questions about silencers. Although I think the answers have already been given, they are perhaps not worded exactly as he asked the question, so today I want to spend a little time on the subject. Before I do, here is a linked bibliography on the silencer issue.
Airgun silencers: What's the big deal? Article by Tom Gaylord
Airguns and noise Blog Feb 8, 2006
Guilty! Jury finds airgun silencer illegal Blog July 18, 2006
What about a silencer for your airgun? Blog May 2, 2005
This is (very) off-topic, but I wonder if you would be so kind as to address an air gun topic that is "loaded" (pun fully intended). This regards the sensitive issue of air gun "silencers", "moderators", "shrouds", "dampers", or whatever name that people care to call these devices. Specifically, my inquiry involves an assertion by Dr. Beeman ("Silencers on Airguns" -an article that can be found on his website) that shrouds, moderators, etc, besides being (in his opinion) illegal, are also, according to him, ineffective in reducing the report of any "springer" type of air rifle.
I am not concerned here with the legality issue, but rather the assertion that these devices do not work on airguns. His logic is that though the moderators may be effective on CO2 guns and PCP's because of the fact that they involve allowing the slower expansion of a large volume of air rushing from the gun upon discharge, that this is NOT the case with springers since springers merely use a cusion of air as a medium for transfer of the energy of the expanding spring to the pellet, and so, in his opinion, the moderator does nothing to dampen the sound of the spring air rifle. This seems contrary to both common sense as well as observation to me for the following two reasons;
1) I notice a definite difference between my (very loud) Webley .177 Tomahawk and the sound of a TX200 in the same caliber being discharged (though I do know that the Tommy is more powerful) and;
2) Noise inside of a structure, such as a home, can be "dampened" or moderated by the use of special building techniques involving more insulation and a second layer of wallboard held to the studs by special clips which allow the wallboard to move and cancel the transfer of sound.
It seems to me that dampening the noise from an airgun would similarly involve allowing vibrations to be muffled by an expansion chamber (such as a moderator or shroud), and that the noise of the rifle firing is not solely generated by a large blast of air such as issues from a PCP or CO2 rifle. For that matter, my QB-78 is very quiet and has NO moderator or provision for sound reduction other than a rather long barrel, yet it is very quiet. Further, it seems that these devices would not be so popular in the countries of Europe where they are legal, if they were not effective. I am very interested in reading your opinion on this matter. Thanks for putting up with my (verbose) and lengthy rant on this matter, and thanks also for your attention and consideration.
Dr. Beeman is correct about the "noise" of a spring gun. Most of it is transmitted through the bones of the shooter's face, so the sound is much louder for the shooter than for those standing close by. Thomas Edison was deaf and listened to the phonograph he invented by biting on the wooden case of the instrument, so he was intimately familiar with the sound conductive properties of facial bones.
It is possible to muffle the muzzle report of any airgun with a silencer, however. As quiet as spring guns are, the TX200 is further muffled by the use of a shrouded barrel containing a baffled silencer. It works, but the payoff is very slight. The TX200 is also a very smooth spring gun, and that, alone, reduces the noise. So, yes you can silence a springer, but why would you want to? An exception is a gas spring gun, whose gas-driven piston produces a small crack of sound upon discharge. But a well-adjusted spring gun is already very quiet (EXCEPT TO THE SHOOTER!). Curtis, you need to let someone else shoot both guns and you listen to the report. The TX will be louder than the Tomahawk, but not by as much as you think.
So why is Curtis' QB78 so quiet? Because by the time the pellet exits the muzzle, the gas pressure has dropped relatively low, and it doesn't have enough remaining energy to make a loud sound. This is the same reason all spring guns are quiet. Because they use so little air, there is no energy remaining by the time the pellet leaves the muzzle.
I'll leave you with this thought. In the 1980s, certain printers were extremely noisy. The Lexitron word processor printer was so loud (either 92 or 96 dB, as I recall) that it had to have an acoustic shield over it at all times. It was an impact-type daisy wheel, if that means anything to you. But times changed. Today's office printers are so quiet that they cannot be heard in most offices. They use different technologies, of course, but the fact is that they're quiet. You could lower their noise signature even more by putting an acoustic shield around them, too, but why would you want to?