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Acoustic Lab Testing Report - Click Here!

Standards: ASTM E492-2016, ASTM E90-2016

Project Duration: 2018 - 2020
Energy Studies in Buildings Laboratory (ESBL), University of Oregon (UO)
TallWood Design Institute (TDI)
U.S. Economic Development Agency
Riverbank Acoustic Laboratories, Geneva, Illinois
USG Testing Services, Corporate Innovation Center, Libertyville, Illinois
Research Team:
Kevin Van Den Wymelenberg, University of Oregon (UO), ESBL
Mark Fretz, UO, ESBL
Dale Northcutt, UO, ESBL
Design Advisory/Industry Feedback Group:
DCI Engineers, Glumac, Hacker Architects, Scott Edwards Architecture, FFA, ZGF, Creative Acoustics NW, ARUP, CSDA Design Group, Swinerton Builders, Erica Fischer (Oregon State University College of Engineering), KPFF, WoodWorks

The upper portion of the acoustic testing chamber at Riverbank Acoustic Laboratories, with the bare CLT assembly installed. The blades above oscillate and distribute noise from the speaker (the black box in the middle of the room). 

TallWood Design Institute a CLT panel set up for acoustic testing

Above: Acoustic underlayment and Durock cement board being installed over the bare CLT assembly for the second dry floor assembly test.

Above: 1/2" nylon carpet installed, as part of the third and final iteration of the dry floor assembly testing. 


Mass timber products are growing in popularity, particularly in multifamily residential dwellings, for which they are structurally well-suited. However, acoustic performance of these products has not been robustly tested, which can be a hindrance to building projects due to lack of code compliance or building performance with poor acoustics. The latter is particularly important since the sound transmission class (STC) rating—a single number used to characterize decibel attenuation—does not characterize an assembly in terms of which frequencies it blocks well or transmits. Wood does a good job of attenuating mid- to high-range frequencies, but not necessarily low ones, such as from a sub-woofer, so testing of assemblies is critical because it elicits their performance in terms of the entire range of frequencies, in addition to defining a single STC rating. This allows for adjustments to be made that balance the acoustic performance of the assembly – such as adding isolation through solutions like air space or concrete topping – with construction cost, sequencing and aesthetics. The other standard acoustic rating, impact insulation class (IIC), accounts for foot-fall and other impact noises and is another critical test for determining code compliance of floor assemblies.

In order to address the need for more acoustic data on mass timber assemblies, TDI awarded funding, including part of an EDA grant, to the ESBL in 2018 to conduct acoustic field testing on existing mass timber buildings and ASTM-certified laboratory testing of both dry and wet (concrete-composite) assemblies using CLT and MPP.
To produce immediately relevant CLT and MPP acoustic data for engineers, designers and contractors in order to remove barriers for project implementation.

Above: The lower portion (receiver space) of the acoustic testing chamber at Riverbank Acoustic Laboratories. In the foreground is an oscillating microphone, that averages incoming noise in the space by rotating. 


Mass timber products being tested:

Cross laminated timber 
Characteristics: five-ply (6 7/8"), Douglas fir
Topping: See assemblies below

Mass plywood panels 
Characteristics: 6" thickness, Douglas fir
Topping: See assemblies below

Dry assemblies being tested (all include CLT and MPP):

Above: Walls 1, 2, and 3 (respectively, from top to bottom). 
NOTE: Some minor details of these assemblies may have changed for testing

Wall 1: Bare timber assembly 
Wall 2: Timber with 5/8” gyp.
Wall 3: Timber, Sopraseal stick 1100t, four-inch mineral wool, one-by-four inch wood battens, one-by-six inch T&G cedar siding  

Floor 1: Bare timber assembly

Floor 2: Timber, 1-inch acoustic underlayment, three-and-a-half-inch Durock cement board, two 5/8-inch oriented strand board, 1/8-inch acoustic underlayment, 1/2 T&G pine floating floor

Floor 3:  Timber, one-inch acoustic underlayment, (3) ½-inch Durock cement board, Two 5/8-inch oriented strand board, 3/8-inch carpet pad, 1/2-inch nylon carpet

Concrete-composite assemblies being tested (includes iterations in CLT and MPP):




Floor 1: Timber with 2 ¼-inch slab at 145 pcf density, connected by self-tapping screws and number 3 rebar
Floor 2: Same as “Floor 1”, with additional: 1-inch acoustic underlayment, Two 5/8-inch oriented strand board, 1/8-inch acoustic underlayment, 1/2-inch T&G pine floating floor  


STC and IIC Laboratory testing timeline:

February 2019: Dry CLT floor and wall assemblies; Dry MPP wall assemblies
March 2019: Concrete-composite CLT floor assemblies; Dry MPP floor assemblies; Concrete-composite MPP floor assemblies

***Results will be made available at the Institute for Health in the Built Environments May 2019 Research Symposium in Portland, OR. Contact ESBL for more details.