Archived posting to the Leica Users Group, 2008/11/01[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
At 05:05 PM 11/1/2008, Eric Korenman wrote: >My son and I were playing today -- we were making bomb whistle >noises.. y'know, standard father and son stuff > >I suddenly realized I couldn't tell him WHY bombs whistle with that >falling pitch sound. >I'm certified comp sci, physics nerd too.. >Google didn't help either! > What is "comp sci"? I am rather hostile to cutsey phrases like this: if you want to say something, say it. There are various causes for various noises made by incoming ordnance. If you are asking about the whistling sound so beloved of Hollywood for bombs dropped from airplanes, this is more an artifact of the past than of the present: current bombs are far more aerodynamic for the most part and therefore a lot quieter. In World War II and Korea, the standard heavy-bomber weapon was just a drum filled with explosives. The British called this a "cookie" for reasons which remain obscure. A drum will tumble as it falls, thus generating a fair amount of wind noise. Even bombs which were externally carried and which were therefore given some regard to aerodynamic efficiency, ended up being rather crudely designed to accommodate production efficiencies. So, yes, all of these bombs did produce some noise while falling. The change in pitch is produced in most cases by "dopplering" -- a bomb falling some distance away will compress sound waves as it builds up speed and then will decompress them as it factors away from the listeners' location. A Wikipedia or Google search for "doppler" might be illuminating. The same effect explains that drop in the pitch of a railroad whistle as the train passes by. (I have lived in railroad towns for decades -- the 3:15 CSX freight this morning gave a perfect example of this as it passed about three miles from my house. this morning. I do know some folks with strongly technical backgrounds who study these things -- most of them play around with explosive devices for a living, some with gummit jobs and some working for private industry (that is, "merchants of death", in terms familiar to an older generation). I will be happy to ask some of them about this if you contact me off-line but be warned that their responses will probably soon turn into mathematics incomprehensible to those who do not regularly deal with such matters. But, the short answer is that the mass production of bombs carried internally led to the use of drum-shaped bombs which were not aerodynamically sophisticated and so which produced a lot of noise while falling. And the Doppler effect generally explains the change in pitch as the bomb falls. Marc email@example.com Cha robh b?s fir gun ghr?s fir!