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This will be the theory behind noise reduction with no specifics. The noise produced by a firearm is comprised of three elements. 1) the sonic boom of a bullet travelling faster than the speed of sound, 2) the noise of the action, and 3) the sound of the report. When concerned with handguns 1) is easy to accomplish by using sub-sonic ammo, that which travels under about 1100 fps. 9mm 147gr loads, most .45 ACP ammo, and standard velocity .22 lr would fall into this category. Sometimes rifles are supressed and sub-sonic ammo is not used. For some reason the shots sound as though they are coming from 90-180 degrees away from the actual point of origin. A very odd sensation. Action noise is a concern when using a semi-auto or full auto action as it throws empty brass all over and the bolt slaps back and forth. Ingram developed a ceramic washer for the bolt face of the MAC-10's that would help cut down on that noise so two pieces of metal would not be slapping together 800 time a minute. A revolver is not a good choice as the cylinder gap does not completely contain the burning gases. A single shot or bolt action is a good choice and some semi-auto pistols are equiped with a slide lock device turning them, effectively, into single shots. Lastly is the report. That noise is the result of a rapid, uncontrolled expansion, of hot gases. To reduce that noise you must cool the gases and control the expansion rate by redirecting them and slowing them down. Try a search on the Welrod pistol. It is a WWII British suppressed single shot pistol in .32 ACP which will illustrate how each of the three elements of noise were tackled. Good luck with the paper. See, no specifics on how, just theoretical information on what needs to be dealt with. You might try contacting AMF (American Machine and Foundry), the former owners of Harley-Davidson Motorcycle Company, they did alot of work for the govt studying this stuff and they may be able to tell you where to get a copy, from the govt under the FOIA, of the report they did.
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