Status: Urban Legend
The Miami Herald
reports the case of a man who threatened to shoot the mother of his child with a gun silenced by a potato. He never fired the gun, but did explain to her how the potato would silence the shot, insuring that no one would hear what happened. The police had this to say about the man's knowledge of acoustics:
The vegetable, while rich in carbs, does not make an effective silencer, police say. The myth dates back to mob murders of the 1920s and has persisted through movies and word of mouth.
"It was fine in Dick Tracy, but in real life, it's not true," said Miami-Dade Sgt. Bob Hoelscher, a longtime firearms technician who is not involved in the case. The sound of a gunshot can be suppressed somewhat if the gun is low-caliber and the cartridge is weak enough, Hoelscher said. But it usually makes a mess.
Detectives seized a 9mm Ruger pistol from Thompson.
"You're going to have potato salad 360 degrees from the muzzle," Hoelscher said. Of course, people haven't stopped trying.
Another favorite, often seen in movies and on TV, is to tape an empty plastic soda bottle onto the muzzle of the gun. I don't think this works any better than the potato technique. The Insultingly Stupid Movie Physics
Page points out that movies, in general, tend to grossly misrepresent the effectiveness of silencers. In real life they don't silence guns as much as they do in movies. (I should note that I've never handled a gun, so I'm relying entirely on the word of other sources here.):
Cutting sound intensity in half only reduces the relative loudness by merely 3 dB. This would be barely noticeable. A good set of ear plugs typically reduces noise by about 30 dB and so, would reduce a muzzle blast from 150 to 120 dB, still a very loud noise. We estimate that the innocuous "fut" sound made by a movie silencer is roughly 50 dB 7, a whopping noise reduction of 100 dB from the dB level of a muzzle blast! In other words, a silencer has to reduce sound intensity of a muzzle blast by a factor of 1010 to give such a low relative loudness. This can be done with a very well designed and precision made silencer using subsonic ammunition. However, even commercially available silencers are more likely to give a reduction of 30 to 40 dB similar to ear plugs, than the incredible 100 dB reduction frequently portrayed in movies, especially when used on high-powered rifles.
(via David Emery