STC Comparisons:

Material Material STC Std Construction STC 110dB Stereo playing adjacent room 5/8” Gypsum 20 38 72dB (nearly as loud as a lawnmower) Homasote 23 45 65dB (similar to a loud conversation at 3 feet) QuietRock Ultra 64 75 35dB (barely perceptable, quieter than a library)

NK-520 QuietRock Standard

NK-520 is fabricated using our revolutionary NK-311 viscoelastic adhesive. This is available in a standard 4’ x 8’ sheet (or 4’ x 12’ special order), weighs 120lbs and is shipped motor-freight. It is ready-to-use, and can be used in place of standard drywall, or on top of existing drywall. NK-520 alone has an STC rating of 42 (regular drywall is 20-24 by itself). Walls and ceilings can be easily constructed with STC ratings of 45-50 using NK-520.

NK-521 QuietRock Ultra

NK-521 is fabricated using our revolutionary NK-311 viscoelastic adhesive plus a special closed-cell vinyl sound barrier. This is available in a standard 4’ x 8’ sheet (or 4’ x 12’ special order), weighs 170lbs and is shipped motor-freight. It is ready-to-use, and can be used in place of standard drywall, or or on top of existing drywall. Using NK-521, walls and ceilings can be constructed with STC ratings of 55 to 65.

This product has some of the highest STC ratings (amount of sound isolation) of any interior wall system in the world. Each plywood/viscoelastic damping layer combination has an STC alone of 42. With two of these layers, plus a vinyl barrier (which has an STC of 26 alone), the NK-521 has an STC rating of 64 by itself (standard drywall is 20-24 by itself).
Using NK-521 with typical construction, walls and ceilings can be easily constructed with finished STC ratings exceeding 75-80, depending on construction techniques.