I found an assembly that meets the sound transmission requirements of the project. How does changing the materials affect the STC rating?

The sound transmission class (STC) rating of gypsum board (GWB) stud partitions depends on a variety of factors. Some general guidelines are outlined below:

• A decrease in wall density would result in an increase in the STC rating.
• Lightweight steel studs, such as 25-gauge steel will provide higher STC ratings than wood or S-J structural studs. Systems using resilient channel with Wood and S-J structural studs have a comparable, or slightly better, sound isolation compared to 25 gauge metal studs.
• 25 gauge steel studs will provide approximately a 5-6 STC point increase compared to wood or S-J structural studs.
• Increasing the stud depth for both metal and wood studs results in a modest STC increase.
• 25 gauge steel studs will provide approximately a 3 STC point increase for each doubling of stud size. Wood or S-J structural studs provide an approximate 1-2 STC point increase for each doubling of studsize.
• Increasing the stud spacing to 24" from 16" on center will result in a slight increase in STC rating. For 25 gauge steel studs this increase would be approximately 1 STC.