excess noise or self noise

["hartogj" hartogj]

Hi David,

> Excess noise is precisely defined as
> microphone noise in excess of the thermal noise of the air. "Self
> noise" is a description which is rarely defined, if ever, in
> comparison with the irreduceable thermal noise.

Given microphone specs typically include either self-noise or SNR figures, 
though never that I have noticed "excess noise" figures, for practical purposes 
how do we determine excess noise?  What do these figures look like when 
included on a spec sheet, how do we use them to determine the qualities of a 
mic compared to using self-noise figures?

John Hartog
rockscallop.org