Re: I choked on buying "Quiet Rock"
Well, the big advantage of QR is space and labor costs. They claim with the 5/8" version a 3-5 layer equivalency to sheet rock. Obviously that's a big difference in space required. As to labor, consider proper installment of sheet rock which requires staggered seams, taping and sealing each layer, and screwing and glueing each layer. That's a lot of labor costs. The QR really works.
In a room like Jerry's, isolation was not really the issue. He has little or no outside traffic. His neighbors are not too close. I don't think he needed more than 2 layers of sheet rock.
As to floor transmission in an apartment building, good luck. You will be able to stop mid and high frequencies, eliminating voice transmission but the bass travels through the structure and will come right up the walls.
Bob Hodas Acoustical Analysis
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