Great piece, Jeff. Just a couple of thoughts:
- An STC rating is got by curve-fitting the lab-measured, 1/3-octave-band TL data from
125 to 4000 Hz; a wider range than the 500 to 2000 Hz indicated in the article.
- I was happy to see editorial mention of utilizing the absorbent properties of drywall at low frequency to advantage in small room design -
and how difficult a process it is! While difficult, if a designer is already involved, the right combination of a high-STC wall, like poured concrete, with an interior "finish" of studs and drywall (leaving the appropriate airgap, of course) could yield outstanding results. It's not as easy as it sounds though. The variables are the mass of the drywall, the depth of the cavities, the amount of absorption in the cavities, the spacing between the studs, etc. In all likelihood, all these will have to be varied considerably to make the results worth the trouble. Of course, while this could help reduce the need for "tweaks" like DRC or overly-large "traps," the design and construction costs will also be substantially higher, thus introducing another (sometimes the most important) variable...
These two comments aside,
nice work!