Off topic, Was: Music Glossary - 1.64 Concert Pitch (2.12.2)

[Mats Bengtsson]

Hans Aberg wrote:
> The speed of sound in gases is (roughly) proportional to the 
> square-root of the absolute temperature. Figures used the speed of 
> sound v_0 in air at 0℃ varies a bit in the range from 331.2 to 331.8 
> m/s perhaps. This gives the formula at absolute temperature T
>   v = sqrt(T/273.15)*v_0 m/s
> For example, if the temperature of the air is 28℃, then T = 273.15+28 
> = 301.15 K (Kelvin). If v_0 is set to 331.5 m/s, then at 28℃, v = 
> sqrt(301.15/273.15)*331.5 = 348.1 m/s. Translated into pitches, this 
> is a change of 25.4 cents relative the speed 343 m*/s given above, or 
> a difference in tuning of about 6-7 Hz, or enough to hear the 
> instrument go out of tune. (But the temperature of the air varies 
> throughout the instrument - I just took a value to show how to 
> calculate v.)
A flute playing friend of mine once demonstrated what happens if you 
drink a bear just before you play and all of  a sudden a burp increases 
the proportion of carbon dioxide in the breathing air significantly, 
resulting in a much lower pitch.

  /Mats