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<blockquote data-quote="Bennett Prescott" data-source="post: 42288" data-attributes="member: 4">Re: Airplane faster than a speeding bullet?Kristian,Air pressure is not the same as air density, the two have a more or less equal and opposite effect for our purposes and cancel. The effect on the speed of sound of air pressure is minute compared to that of temperature, and even to that of humidity. From 1-5 atmospheres of pressure there is only a 0.5 m/sec increase in the speed of sound. From 0-100% humidity there is about a 2.5 m/sec increase in the speed of sound. Meanwhile, going from -13°C to 47°C there is a 40 m/sec difference in the speed of sound. Many (often aviation) graphs of speed of sound vs. altitude also include temperature and therefore confuse the issue.<a href="http://www.sengpielaudio.com/calculator-speedsound.htm" target="_blank">http://www.sengpielaudio.com/calculator-speedsound.htm</a><a href="http://en.wikipedia.org/wiki/Speed_of_sound#Dependence_on_the_properties_of_the_medium" target="_blank">http://en.wikipedia.org/wiki/Speed_of_sound#Dependence_on_the_properties_of_the_medium</a><a href="http://www.phy.mtu.edu/~suits/SpeedofSound.html" target="_blank">http://www.phy.mtu.edu/~suits/SpeedofSound.html</a></blockquote>

[QUOTE="Bennett Prescott, post: 42288, member: 4"] Re: Airplane faster than a speeding bullet? Kristian, Air pressure is not the same as air density, the two have a more or less equal and opposite effect for our purposes and cancel. The effect on the speed of sound of air pressure is minute compared to that of temperature, and even to that of humidity. From 1-5 atmospheres of pressure there is only a 0.5 m/sec increase in the speed of sound. From 0-100% humidity there is about a 2.5 m/sec increase in the speed of sound. Meanwhile, going from -13°C to 47°C there is a 40 m/sec difference in the speed of sound. Many (often aviation) graphs of speed of sound vs. altitude also include temperature and therefore confuse the issue. [url]http://www.sengpielaudio.com/calculator-speedsound.htm[/url] [url]http://en.wikipedia.org/wiki/Speed_of_sound#Dependence_on_the_properties_of_the_medium[/url] [url]http://www.phy.mtu.edu/~suits/SpeedofSound.html[/url] [/QUOTE]

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