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A little technical information on the speed of sound and the temperature of the atmosphere, since there seems to be some confusion. Speed of sound has nothing to do with density, except that density can be related to temperature through pressure. This makes sense when you stop to think about it. Temperature is the measure of the average energy of a group of molecules, which is related to their average speed. Sound is transmitted by collision of molecules, so it's transmitted at something close to the average speed they're moving. Density doesn't really matter, since you can have those collisions with just a handful of molecules. For those that want the equation, here it is: a = sqrt(gamma*R*T) where a is the speed of sound, gamma is the ratio of specific heats (constant pressure vs. constant volume = 1.4 for air), R is the specific gas constant (1716 ft*lb/slug :R for air), and T is the temperature in Rankine (Fahrenheit + 459.67). To describe the temperature of the atmosphere better, like someone else said in a previous message, temperature doesn't continually drop off as you increase altitude. There are three isothermal regions where the temperature stays constant over a wide range of altitude. Above the first one of those, temperature actually increases as you go higher. Between the second and third, it drops again, and above the third, it starts increasing again. At least according to the standard atmosphere. Above that, I don't know what it does, because none of my engineering books go up that high. -Jeff Lewis __________________________________ Do you Yahoo!? Yahoo! SiteBuilder - Free web site building tool. Try it! http://webhosting.yahoo.com/ps/sb/ ========================================================================== ==== To leave this forum go to: http://ercoupers.com/lists.htm Search the archives on http://escribe.com/aviation/coupers/
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