STC 2. Sound Dampening Techniques Flashcards
Adding absorptive insulation (e.g., fiberglass batts) in the wall cavity increases the STC to:
36-39, depending on stud and screw spacing. Doubling up the drywall in addition to insulation can yield STC 41-45, provided the wall gaps and penetrations are sealed properly.
Typical interior walls in homes (1 sheet of 1/2″ drywall on either side of a wood stud frame) have an STC of about:.
33
Why does doubling the mass of a partition double the STC?
It DOES NOT.
Doubling the mass (going from two total sheets of drywall to four, for instance) typically adds 5-6 points to the STC. Breaking the vibration paths by decoupling the panels from each other will increase transmission loss much more effectively than simply adding more and more mass to a monolithic wall/floor/ceiling assembly.
Structurally decoupling the drywall panels from each other (by using resilient channel, steel studs, a staggered-stud wall, or a double stud wall) can yield an STC of:
as high as 63 or more for a double stud wall (see table below), with good low-frequency transmission loss as well. Compared to the baseline wall of STC 33, an STC 63 wall will transmit only 1/1000 as much sound energy, seem 88 percent quieter and will render most frequencies inaudible
Materials which can improve STCs in walls include:
mass-loaded vinyl (MLV), standard drywall, “soundproof” drywall (such as QuietRock, Supress, SoundBreak, or ComfortGuard) and damping compounds such as Green Glue.
attenuation
To reduce the amplitude of ( a wave)
In serious cases (e.g., a bedroom adjacent to a home theater room, and an inconsiderate nocturnal neighbor, to boot) a partition to reduce sounds from high-powered home theater or stereo should ideally be STC of
70 or greater, and show good attenuation at low frequencies
An STC 70 wall can require detailed design and construction and can be easily compromised by
‘flanking noise’, sound traveling around the partition through the contiguous frame of the structure, thus reducing the STC significantly.
Luxury multifamily units, dedicated home theaters, and high end hotels often have walls designed with an STC rating of:
STC 65 to 70
Sound Transmission Class (or STC) is an integer rating of how well a building partition
attenuates airborne sound. In the USA, it is widely used to rate interior partitions, ceilings/floors, doors, windows and exterior wall configurations
Single layer of 1/2″ drywall on each side, wood studs, no insulation (typical interior wall)
33
Single layer of 1/2″ drywall on each side, wood studs, fiberglass insulation
39
4″ Hollow CMU (Concrete Masonry Unit)
44
Roxul Safe’n’Sound Insulation installed between wood 2 × 4 studs on 16″ centers and 5/8″ drywall (type x ) on each side with resilient channels at 16″ on one side [4]
45
Double layer of 1/2″ drywall on each side, wood studs, batt insulation in wall
45
Single layer of 1/2″ drywall, glued to 6″ lightweight concrete block wall, painted both sides
46
6″ Hollow CMU (Concrete Masonry Unit)
46
8″ Hollow CMU (Concrete Masonry Unit)
48
10″ Hollow CMU (Concrete Masonry Unit)
50
8″ Hollow CMU (Concrete Masonry Unit) with 2″ Z-Bars and 1/2″ Drywall on each side
52
Roxul Safe’n’Sound Insulation installed between steel 2 x 4 studs on 24″ centers and 5/8″ drywall (type x) on each side [4]
52
Single layer of 1/2″ drywall, glued to 8″ dense concrete block wall, painted both sides
54
8″ Hollow CMU (Concrete Masonry Unit) with 1 1/2″ Wood Furring, 1 1/2″ Fiberglass Insulation and 1/2″ Drywall on each side
54
Double layer of 1/2″ drywall on each side, on staggered wood stud wall, batt insulation in wall
55
