Sound Trivia: Shooting in Heat by Airports
This awkward title covers cold temperatures as well.
Currently we are hitting 32C/89F around London and apart from battling the heat physically and mentally it is an interesting, though minor, consideration to the speed of sound and the further implications to issues of noise from planes and trains. Sound at sea level travels at 340.29 meters / second (768.1) but at 32C sound travels around 10m/s faster at 350.3 m/s (783.6mph) due to hot air having molecules closer together to become a better conductor. this is NOT to do with the sound being louder because the amplitude of the wave doesn't change just the speed it is carried.
This just means that any planes flying over at 21,000 feet will be heard roughly 18.28 at 32C and just 18.82 seconds at 20C meaning half a second quicker coming and going effectively being 1 second shorter in disturbance.
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All Calculations are made via this awesome widget. type in The Speed of Sound widget below to look up the speed at which sound waves travel in many different materials. Simply type in the name of the material. For instance, water, helium, air, air at 45 deg C (or any other material and conditions) into the blank; then click the Submit button.