The stc rating of a cmu wall can be estimated based on its weight using the following formula.
Stc rating for solid concrete walls.
Common stc ratings international building code requires 50 stc between adjacent dwelling units.
The estimate could easily be off by as much as 4 db.
Stc 20 50 234w eqn.
5 contains similar requirements but with a minimum stc rating of 45 db when tested in accordance with astm e90 for walls and floor ceiling assemblies separating dwelling units.
1 stc sound transmission class is the usa rating used to characterize airborne noise insulation.
A wall system with higher stc rating is more effective in preventing the transmission of sound.
Adding absorptive material within the partition a partition is given an stc rating by measuring its transmission loss over a range of 16 different frequencies between 125 4000 hz.
The international residential code ref.
Determining sound transmission ratings for masonry walls tms 0302 ref.
125 4000 hz is consistent with the frequency range of speech.
An empty framed wall steel studs and a layer of gypsum wallboard on each side has an stc of approximately 35.
Although that ll help you meet code it doesn t mean it s sufficient to block out the noise tenants expect.
Stc ratings for wall floor and window materials and assemblies 3 appendix a stc ratings a 1 walls a 1 exterior a 1 interior a 9 wooden studs a 9 metal studs a 14 floors a 16 wood a 16 concrete a 21 windows a 24 doors a 27 exterior a 27 interior a 29 appendix b references b 1.
All too often this plenums and suspended ceilings unbaffled ducts window to window outdoors common heating units transoms and air grilles unblocked joist spaces uncaulked wall perimeters ducts piping and fixtures masonry joints.
The stc rating does not assess the low frequency sound transfer.
Note that in the low frequency range important for music theaters traffic aircraft and most other real world noise sources the lower stc wall is literally 30 decibels better yet lower stc.
One has an stc 47 4 solid concrete the other an stc 48 steel stud wall.
According to the standard stc can be determined by field or laboratory testing in ac cordance with standard test methods or by calculation.
Where w pounds per square foot psf this information is provided as a tool to help estimate.
A wall system with higher stc rating is more effective in preventing the transmission of sound.
Stc 0 18w 40.
Doubling the mass of a wall assembly does not double the stc rating.
The calculation in tms 0302 is based on a best fit relationship between concrete masonry wall weight and stc based on a wide range of test results.
