Architecture

STC Rating Estimator

Build up a wall or floor assembly from common layers and we'll estimate STC. Useful for early acoustic spec — lab-tested assemblies trump estimates for real submittals.

Wall assembly

Framing Insulation in cavity Drywall — side 1 Drywall — side 2 Resilient channel / clip system

STC reference

STC 30: Normal speech audible through wall
STC 40: Loud speech audible as murmur
STC 45: Loud speech barely audible. IBC minimum for residential party walls.
STC 50: Loud speech inaudible. Good apartments / hotel rooms.
STC 55: Very loud sounds (music, TV) just audible. Premium residential.
STC 60+: Loud speech and music inaudible. Recording studios, theaters.

FAQ

What's STC measuring? +

Single-number Sound Transmission Class. Measures airborne sound (speech, music) transmission across an assembly. Higher = better.

STC vs IIC? +

STC = airborne sound. IIC = impact sound (footsteps). Both matter for floor/ceiling assemblies; only STC matters for walls.

Code minimums? +

IBC residential party walls: STC 50 lab / STC 45 field. Office demising walls: STC 40-45 typical. Hotel rooms: STC 50+.

Why do estimates differ from lab tests? +

Real-world performance depends on flanking paths (sound around the wall via slab, ceiling, windows). Lab tests are best-case. Field STC ~5 points lower.