2a.3 Temperature effects
The speed of sound varies with air temperature:
This means that the speed of sound can vary from 331.5m/s to 354.9m/s between 0ºC
and +40ºC.
Temperature Gradient
As mentioned in Section 2a.2, air is a poor heat conductor and relies on its contact
with surfaces to heat up and cool down.
On a clear, warm, sunny day the ground will warm low level air and the atmosphere
will heat up, by convection, from bottom to top. Warm air cannot rise to the top of the
atmosphere because air pressure drops with height and air temperature falls as the
pressure falls.
Sound will travel faster near the ground and slower higher up causing its path to be
tilted upwards.
30m
20m
10m
0m
0m 10m 20m 30m 40m 50m 60m 70m 80m 90m
Sound path tilting upwards outdoors due to normal
temperature decrease with height
Cooler
Warmer
All material © 2007. Martin Audio Ltd. Subject to change without notice.
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