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Re: frequency dependence of sound speed

For the usual reasons: labeled as 'dispersion'.
This dispersion is not noted for the usual audible range say 20 to 20 kHz
but ultra sonic waves can (apparently) approach a natural frequency
of absorption.

From an old CRC Handbook (for still air, 20C, 0% humidity, pressure
unspecified)

f (Hz) v (ft/sec)
20 1126.89
40 1127.01
100 1127.13
400 1127.17
2000 1127.17
4000 1127.18
20000 1127.19
80000 1127.19


The biggest effect (albeit still rather modest) seems to be at low
frequencies. At least up through 80,000 Hz, ultrasound seems to have
little or no change in speed.


Tim F