Just how do you calculate STC ratings?

For those of you that want to know how to calculate STC, here it is:

Measure the transmission loss (TL) for the wall system from 125 Hz to 4 kHz and plot on a chart.  The STC for the wall is determined by superimposing a contour chart (not shown here) upon the TL curve such that (1) there is no more than a 8-dB deficiency between the TL and the STC contour at any 1/3-octave frequency (i.e., no test point may be more than 8 dB below the STC contour), and (2) the total deficiency between the STC contour and the TL curve (i.e., the value of the STC contour minus the value of the TL curve summed at all 1/3-octave frequencies from 125Hz to 4 kHz) must be less than or equal to 32 dB.  Once the curve has been adjusted to met these two criteria, then the STC value of the wall is equal to the TL value of the contour at 500 Hz.

Makes sense?  Not really!

Best way to say it is:  The more noise the wall system reduces – the higher the STC number.