Core idea: Use airborne isolation ratings without treating one number as a guarantee.
What STC summarizes
It condenses tested airborne transmission over a defined frequency range.
What it misses
Very low-frequency bass and flanking may be poorly represented.
Lab versus field
Workmanship, penetrations and connected construction reduce field performance.
Read the test
Confirm the exact studs, layers, insulation, channels, fasteners and seals.
A practical planning sequence
- Describe the source, timing and frequency character.
- Trace direct and flanking paths.
- Set a realistic improvement goal.
- Compare complete systems and local requirements.
- Document the baseline and inspect details during work.
- Repeat the same test afterward.
What cannot be guaranteed online
No website can promise a specific reduction in an unknown building. Field results depend on construction, workmanship, connected structures, openings and the source.
Written by Martin R. Calderwood.