Acoustic Performance
QUIETER SPACEs, BETTER COMFORT
TimberHP wood fiber insulation helps reduce airborne sound transmission through its dense, porous fiber structure, creating quieter interior environments.
STC Performance Compared
2×4 Wood Stud Cavity
Understanding STC Ratings
Sound Transmission Class (STC) is the industry-standard rating used to measure how effectively a wall, floor, or ceiling assembly reduces airborne sound.
The higher the STC rating, the more sound is blocked.
| STC Rating | What You Hear |
|---|---|
| 30 | Speech easily understood |
| 40 | Speech difficult to understand |
| 50 | Great sound isolation. Speech heard only as a murmur |
| 60+ | Excellent sound isolation |
Even small increases in STC can noticeably improve privacy and occupant comfort. A 10-point increase is generally perceived as roughly cutting sound transmission in half.
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50,000 sf, TimberBatt Acoustic, Steel stud acoustical assembly.
Why AssemblIES MATTER
Acoustic performance depends on the entire wall assembly, including framing, insulation, gypsum layers, resilient channels, and air sealing details.
While insulation is only one component, TimberBatt has demonstrated strong acoustic performance in third-party testing. The examples below compare STC ratings for similar wall assemblies using different cavity insulation materials.
Tested Performance You Can Trust
The assembly ratings in this guide are based on third-party laboratory testing conducted by Riverbank Acoustical Laboratories (RAL), one of North America’s most respected acoustics testing facilities. These results provide architects, builders, and designers with verified data for specifying high-performance wall assemblies using TimberHP insulation.
Acoustic performance can be measured in different ways depending on the application. Sound Transmission Class (STC) and Outdoor- Indoor Transmission Class (OITC) ratings evaluate how effectively a wall, floor, or ceiling assembly reduces sound transmission from one space to another. Noise Reduction Coefficient (NRC) measures how effectively a material absorbs sound energy within a space.
Together, these metrics provide a more complete picture of acoustic performance—helping designers create buildings that are not only quieter between rooms, but also more comfortable and pleasant to occupy.
MATERIAL SOUND ABSORPTION PERFORMANCE
| Product Name | Thickness | NRC** | RAL Test # |
|---|---|---|---|
| TimberFill | 5-1/2 inch | 1.15 | A22-003 |
| TimberBatt | 5-1/2 in | 1.15 | A22-007 |
| TimberBoard (Single layer) | 1-1/2 inch | 0.85 | A22-004 |
| TimberBoard (Two layers) | 3 inch | 0.85 | A22-005 |
| TimberBoard (Single layer) | 5-1/2 inch | 1.00 | A22-006 |
**Noise Reduction Coefficient (NRC) measures a material’s ability to absorb sound. Higher values indicate greater sound absorption. Values above 0.80 are generally considered highly effective for acoustic control.
WOOD STUD ASSEMBLIES
All assemblies tested by Riverbank Acoustical Laboratories (RAL) in accordance with ASTM E90 and ASTM E413. Results apply only to the assemblies shown.
| RAL Test # | Framing | Insulation | Insulation Thickness | Resilient Channel | Drywall | STC | OITC |
|---|---|---|---|---|---|---|---|
| TL23-011 | 2×4 Wood Studs 16" o.c. | TimberBatt | 3" | No | 5/8" Type X Both Sides | 37 | 27 |
| TL23-012 | 2×4 Wood Studs 16" o.c. | TimberBatt | 3" | Yes | 5/8" Type X Both Sides | 50 | 31 |
| TL23-013 | 2×4 Wood Studs 16" o.c. | TimberFill | Full Cavity (3.5") | Yes | 5/8" Type X Both Sides | 50 | 32 |
| TL23-014 | 2×4 Wood Studs 16" o.c. | TimberFill | Full Cavity (3.5") | No | 5/8" Type X Both Sides | 37 | 27 |
| TL23-015 | 2×6 Wood Studs 16" o.c. | TimberBatt | 5.5" | Yes | 5/8" Type X Both Sides | 55 | 37 |
| TL23-016 | 2×6 Wood Studs 16" o.c. | TimberBatt | 5.5" | No | 5/8" Type X Both Sides | 36 | 28 |
| TL23-017 | 2×6 Wood Studs 16" o.c. | TimberFill | Full Cavity (5.5") | Yes | 5/8" Type X Both Sides | 53 | 38 |
| TL23-018 | 2×6 Wood Studs 16" o.c. | TimberFill | Full Cavity (5.5") | No | 5/8" Type X Both Sides | 38 | 28 |
STEEL STUD ASSEMBLIES
All assemblies tested by Riverbank Acoustical Laboratories (RAL) in accordance with ASTM E90 and ASTM E413. Results apply only to the assemblies shown.
| RAL Test # | Framing | Insulation | Insulation Thickness | Resilient Channel | Drywall | STC | OITC |
|---|---|---|---|---|---|---|---|
| TL23-007 | 3-5/8" Steel Studs 16" o.c. | TimberBatt | 3" | Yes | 5/8" Type X Both Sides | 53 | 34 |
| TL23-008 | 3-5/8" Steel Studs 16" o.c. | TimberBatt | 3" | No | 5/8" Type X Both Sides | 46 | 30 |
| TL23-009 | 3-5/8" Steel Studs 24" o.c. | TimberBatt | 3" | Yes | 5/8" Type X Both Sides | 53 | 32 |
| TL23-010 | 3-5/8" Steel Studs 24" o.c. | TimberBatt | 3" | No | 5/8" Type X Both Sides | 49 | 30 |
FAQ
Everything You Need to Know About TimberHP Acoustic Performance
Get answers to common questions about TimberHP’s acoustic performance, sound control capabilities, building applications, installation best practices, and code compliance.
Q: What is STC and why does it matter?
A: Sound Transmission Class is the industry-standard rating for how effectively a wall, floor, or ceiling assembly reduces airborne sound. The higher the number, the more sound is blocked between spaces.
Q: What’s the difference between STC and NRC?
A: STC and OITC describe how much sound an assembly blocks from passing through it. NRC describes how much sound a material absorbs within a room, reducing echo and reverberation. TimberHP wood fiber performs strongly on both.
Q: Is insulation the only thing that determines a wall’s STC?
A: No. Acoustic performance depends on the full assembly — framing type and spacing, insulation, number and type of gypsum layers, resilient channel, and air sealing. Every rating in this guide applies only to the exact assembly tested.
Q: Do TimberBatt and TimberFill perform differently?
A: Both are rated to an NRC of 1.15 at 5-1/2″. TimberBatt friction-fits for fast cavity installation; TimberFill dense-packs or blows in for full-cavity coverage in retrofit or irregular framing.
Q: Where can I see the raw test data?
A: Every assembly above references its Riverbank Acoustical Laboratories test number (e.g. TL23-007). The full Acoustic Performance Guide includes complete assembly drawings for each one.
THE WOOD FIBER ADVANTAGE
- Dense wood fibers help absorb sound energy for quieter buildings
- Friction-fit installation helps reduce gaps and voids
- Thermal and acoustic performance in one insulation layer
- Delivers industry-leading sound absorption (NRC up to 1.15)