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In every space the common acoustic issue is sound transmission. Sound transmission can be both airborne and/or structure borne. Sound from a noisy environment can cause unpleasant conditions and confidentiality or privacy issues.

Sound Transmission Class (STC) is an integer measurement of a building assembly’s ability to attenuate airborne sound transfer. It is used to rate interior partitions, ceilings, floors, doors, windows and exterior walls. The higher the number, the better the isolation.


What Can Be Heard


Normal speech can be understood quite easily and distinctly through wall


Loud speech can be understood fairly well, normal speech heard but not understood


Loud speech audible but not intelligible


Onset of "privacy"


Loud speech audible as a murmur


Loud speech not audible; 90% of statistical population not annoyed


Very loud sounds such as musical instruments or a stereo can be faintly heard; 99% of population not annoyed


Superior soundproofing; most sounds inaudible


Changes in STC

Changes in Apparent Loudness

+/-  1 STC points

Almost imperceptible

+/-  3 STC points

Just perceptible

+/-  5 STC points

Clearly noticeable

+/-  10 STC points

Twice (or half) as lound


A typical interior wall for residential construction is a single layer of ½" drywall on each side of wood studs with no insulation and has a STC rating of 33. If you add insulation between the studs you will increase the rating to 39.

Interior Finishing Systems can help you achieve STC ratings of 50-60+.

Some of the products we use are:

  • Acoustic Sealants
  • Sound Clips
  • Rc channel
  • Sound dampening drywall
  • Insulation

Please feel free to contact us anytime to see how we can help you build/design your building or home. We can help with rooms such as; home theaters, offices, bedrooms or with your multi-family separation walls.