What is an acceptable STC rating?
Building codes in the USA dictate a minimum laboratory STC rating between multi-family units of 50. However, studies indicate that a STC rating of 55 may be more acceptable to the general public to reduce noise complaints. In general, a 10-point increase in STC will cut the perceived noise level in half. Below are some STC ratings for typical wall constructions and Quietzone™ Acoustic Wall Framing. STC Rating Wall Description Speech Music STC-29 Typical Interior Wall Normal speech heard Music easily heard STC-35 Sealed (QZ caulk) Wall, no cavity fill Loud speech heard Loud music easily heard STC-39 Std Sealed Wall w/ QZ Batts & QZ Caulk Loud speech blurred Loud music muffled but easily heard STC-49 2×4 Single layer drywall w/ QZAWF Loud speech barely audible Loud music greatly reduced. Bass is noticeable. STC-60 and greater 2×6 Double layer drywall w/ QZAWF Loud speech inaudible Loud music inaudible.
