Standalone STC — Material Test
A standalone rating describes the tested material by itself under controlled conditions. It is useful for comparing barrier materials, but it is not the finished wall rating.
SOUND TRANSMISSION CLASS
STC RATINGS EXPLAINED
Understand what STC measures, how material ratings differ from complete wall assemblies, and why the full construction matters more than any single layer.
STC 26
1 LB MLV standalone
STC 32
2 LB MLV standalone
ASSEMBLY
Full system matters
QUICK ANSWER
What does an STC rating tell you?
Sound Transmission Class (STC) is a laboratory-derived single-number rating used to compare how well a building assembly reduces airborne sound transmission across a defined frequency range. Higher STC generally means better airborne-sound isolation.
STC SCALE
What STC Numbers Mean in Practice
STC is a laboratory rating used to compare airborne sound isolation. Use it to compare tested assemblies, but remember that field performance depends on the complete construction and installation.
| STC Rating | What You Hear Through the Wall | Typical Application |
|---|---|---|
| Normal speech clearly audible | Standard interior wall, no insulation | |
| Loud speech audible | Standard construction with batt insulation | |
| Loud speech muffled, barely intelligible | 1LB MLV in standard wall assembly — Target | |
| Very loud speech barely audible | IBC minimum for multi-family party walls | |
| Normal speech inaudible | 2LB MLV in full isolation assembly |
This reference table may be paired with structured data markup where appropriate.
STC Scale — Practical Reference
28
Bare studs
34
+Insulation
26
1LB MLV alone
41
1LB in assembly
32
2LB MLV alone
55+
2LB full isolation
Lab-tested values, not estimates
EnviroFlex™ MLV STC ratings are from third-party laboratory testing. Test certificate available on request.
READ THE RATING CORRECTLY
Standalone STC vs Assembly STC
A material data-sheet rating and a complete wall-assembly rating are not interchangeable. Use the tested configuration that matches the construction you are evaluating.
Assembly STC — Complete Construction
An assembly rating represents the full tested system: framing, insulation, barrier layers, gypsum, channels, fasteners, seams, and other construction details.
SR — Content Columns
LIMITS OF THE NUMBER
What STC Does — and Does Not — Tell You
STC is useful for airborne sound comparisons, but it does not describe every frequency equally and it does not account for every real-world path around an assembly.
ASSEMBLY FIRST
A High Rating Requires the Whole System
Seams, penetrations, framing connections, doors, ceilings, floors, ducts, and other flanking paths can limit the performance of an otherwise strong wall assembly.
PRACTICAL TAKEAWAY
Compare Like With Like
When comparing STC results, look at the complete tested assembly and test conditions—not just one product layer.
PROJECT GUIDANCE
Match the Assembly to the Goal
Use these starting points to decide when a basic mass upgrade may be enough and when a more complete isolation assembly should be considered.
Residential
Target: STC 41
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Studio
Target: STC 50+
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Commercial
Required: STC 50
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Mechanical
Target: STC 55+
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STC FAQ
Common STC Questions
Use these answers to interpret material and assembly ratings more accurately.
Need Help?
Need help choosing MLV?
Compare 1 LB and 2 LB MLV, then use the installation guide to plan the full assembly.
What does STC measure?
STC is a laboratory rating used to compare how well a building assembly reduces airborne sound transmission across a defined frequency range.
Is a material STC rating the same as a wall STC rating?
No. A material-only test and a complete wall-assembly test describe different configurations. For project performance, the tested assembly is the more relevant comparison.
Can I add STC numbers from different products together?
No. STC ratings are not additive. The finished result depends on the full assembly, including framing, layers, insulation, connections, sealing, and flanking paths.
Why can two walls with similar materials perform differently?
Installation details, penetrations, framing, air gaps, structural connections, doors, ceilings, floors, and other sound paths can change real-world performance.
TURN THE RATING INTO A PLAN
Choose the MLV That Fits Your Project
Use STC as one part of the decision. We can help with MLV weight, roll sizing, quantities, and commercial project requirements.
1 LB MLV: STC 26 standalone
2 LB MLV: STC 32 standalone
Assembly results vary
Project support available