Understanding STC Levels

Written By Margaret Thomas

Disclaimer: The content on this blog is for informational purposes only and should not be considered professional advice. Always consult with a qualified expert for legal, medical, or mental health matters. Use your own judgment and discretion when applying any of the ideas discussed here.

Sound Transmission Class, (STC), rates how well a building partition attenuates airborne sound (like voices or music). 

According to the International Building Code, multi-family buildings require an STC level of 50.

Here are the STC levels:

  • STC 25: Normal speech is heard

  • STC 30: Loud speech is still heard

  • STC 35: Loud speech is audible but is not understood

  • STC 40: Loud speech faintly audible

  • STC 45: Loud speech is inaudible

  • STC 50: Loud sounds (loud TV, loud music etc) are faintly audible

  • STC 60+: Good soundproofing

Getting familiar with the various levels will help you to determine the STC level for the building that you live in.

Desk nook with a journal, mug, and warm lamp – wall art says “Your voice matters”

Your voice matters

An image depicting a desk nook with a journal, mug, and warm lamp – wall art says “Your voice matters”

Margaret Thomas
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