STC is roughly the decibel reduction in noise a material/partition can provide, abbreviated 'dB'. The human ear perceives a 10dB reduction in sound as roughly reducing the volume by half. For example, a sound reduction from 50dB to 40dB seems half as loud. This is an important fact to keep in mind when considering a sound solution that ‘fits’ the problem. Don’t over purchase soundproofing material. Consider your budget and your desired acoustic result.
To understand how to soundproof a wall to create a higher STC rating, consider the example of Peacemaker Sound Insulation.
Table of Common STC Ratings
| STC | Building Material/Partition without Peacemaker | What Can be Heard Through Barrier |
| 26-30 | Single Pane Glass Window
| Sentences spoken in a normal
voice can be understood clearly
|
| 30-35 | Double pane window, hollow core wood door,
typical interior wall with single layer of
½’ drywall on each side, no insulation | Sentences spoken in a normal tone of
voice can still be heard with some straining |
| 35-40 | Solid core wood door
| Loud talk can be heard, but
not clearly understood |
| 42-45 | Double layer of ½" drywall on each side,
single batt insulation in wall | Loud talk is somewhat audible, but only occasional words can be understood |
| 47-50 | Single layer of 1/2" drywall, glued to 6" lightweight concrete block wall, both sides painted | Loud talk is audible only by straining
to hear it; music and heavy traffic
will most likely still be heard
|
| 52-55 | Single layer of 1/2" drywall, glued to 8"
dense concrete block wall, both sides painted | Very Loud talk is audible only by
straining to hear it; music and heavy
traffic might still be heard
|
| 57-60 | Double layer of 1/2" drywall on each side,
on wood stud wall, flexible channels on one side, single batt insulation in between | Very loud talk is almost entirely inaudible;
music can barely be heard but bass
notes are still disruptive |
62-65
| Double layer of 1/2" drywall on each side,
on double wood/metal stud walls
(spaced 1" apart), double batt insulation | Music is barely heard- bass notes
make a thumping noise, but
power equipment is clearly heard |
70
| 8" concrete block wall, painted, with 1/2"
drywall on independent steel stud
walls insulation in cavities | Music can be heard faintly if it is played very loud- power equipment is faintly heard
|
| 75+ | | Most noises are effectively blocked,
including airplane noise
|
Additional STC Information:
• When soundproofing rooms, the STC of your doors & windows need to be equal to or greater
than the STC of your walls in order to maximize the rating.
• Structurally decoupling drywall panels from each other (using steel studs, a staggered-stud wall,
double wall stud, or resilient channels) can produce an STC rating as high as 63 (for a double stud wall)
and
will result in effective low-frequency loss. This figure, when
compared to a normal wall with an STC of 33, will make most frequencies
inaudible, making the room sound 88 percent quieter.
• Music-related sounds may require the highest STC ratings. In practical terms, a 55
STC rating will prevent a resident living in a multi-family home from being bothered
at all by their neighbor’s loud music.
• Homes usually require 50-80 STC for sensitive areas, including home theatre walls.
• It’s not always practical to test the entire wall configuration of an assembly to determine the true STC.