A command available in the Query menu if you select a Sound object. The Info window will show the standard deviation (in Pascal) of the sound pressure within a specified window. If the sound contains less than 2 samples, the value is undefined.
The standard deviation is defined as
|1/(t2-t1) ∫t1t2 (x(t) - μ)2 dt|
where x(t) is the amplitude of the sound, and μ is its mean. For our discrete Sound object, the standard deviation is approximated by
|1/(n-1) ∑i=m..m+n-1 (xi - μ)2|
where n is the number of sample centres between t1 and t2. Note the "minus 1".
© ppgb, November 23, 2004