Re: frequency dependence of sound speed

[Brian Whatcott <inet@INTELLISYS.NET>]

At 02:10 PM 12/8/01, you wrote:
> >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

On July 5th, I mentioned a URL with data showing how sound attenuation
versus frequency varies with humidity.
The Rubber book shows how the small variation in c which Tim notes as a
low frequency effect also varies with humidity, so that the effect becomes
ultrasonic at higher humidities.





Brian Whatcott
  Altus OK                      Eureka!