Sheetrock Manufacturing Companies
Historically, most sheetrock manufacturers for regular construction are reasonably honest. They run tests which are reasonably accurate.
Except for Serious Materials ("QuietRock"), in several known cases, these manufacturers have calculated what they think the STC will be without having an actual test performed by an STC lab that can backup their numbers.
Green Glue is a competing product and they have actual STC tests for comparisons.
A Note on Recording Studio Soundproofing
Once you get into recording studio soundproofing, everyone tests their windows.
A recording studio will not talk to a soundproofing company without having the STC tests.
Walls are usually custom built as designed by an accoutic engineer, and are not usually a soundproofing problem.
If you don't have the STC test results for any product, it is not possible to compare to any other products.
Thank you for studying "Soundproofing Lies" with us.
Be sure to check out our other soundproofing courses.