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Advancing Acoustic Performance in Mass Timber: A New Comparative Study on GLT Assemblies

André Rioux

Tuesday, 02 December 2025

As mass timber gains momentum across North America, understanding its acoustic behavior has become one of the most pressing needs in the design and construction community. While the benefits of mass timber are well documented—from reduced carbon impact to construction speed—acoustic performance remains a complex and often under-studied dimension. This challenge is especially evident with GLT (Glued-Laminated Timber) floor systems, where limited publicly available data has historically made confident decision-making more difficult for architects, engineers, and developers.

 

To help fill this gap, FPInnovations and AcoustiTECH have partnered to produce one of the most comprehensive acoustic comparative studies to date, evaluating more than 40 floor–ceiling assemblies built on a 157 mm GLT slab. The result is a new resource designed to bring clarity, consistency, and confidence to professionals working with mass timber systems.

 

FPInnovations: A Leader in Applied Wood Research

 

Few organizations play a role as influential as FPInnovations in advancing the forest and mass timber industries. Their mandate extends across the entire value chain—from forest operations to advanced building systems—making them a cornerstone of Canada’s innovation ecosystem. Their work in wood construction is internationally recognized, driven by applied research that helps transform emerging technologies into practical, real-world solutions.

 

FPInnovations’ state-of-the-art laboratories are uniquely equipped to deepen our understanding of mass timber acoustics. Their facilities support testing in:

  • Structure
  • Acoustics
  • Vibration
  • Fire performance

 

All testing is conducted under ISO 17025-accredited procedures, ensuring that results meet the highest standards of repeatability and scientific rigor. This collaboration with AcoustiTECH leverages decades of expertise from both organizations, merging laboratory precision with field-driven insight.

 

 

Why a Comparative GLT Study Now?

 

Despite the rapid acceleration of mass timber adoption, the industry still faces a significant lack of data—especially when it comes to GLT slabs. Many design teams are forced to rely on scattered reports, past experiences on different products, or adaptations of CLT-based test data. Given how sensitive wood systems can be to low-frequency sound, flanking paths, and connection details, these approximations introduce risk.

 

Recognizing this need, FPInnovations and AcoustiTECH set out to build a robust dataset rooted in real-world constructability. Their objectives were clear:

  • Address the limited acoustic data available for GLT systems
  • Test 40+ assemblies using consistent parameters
  • Use a 157 mm GLT slab paired with 15.8 mm plywood diaphragm as a baseline
  • Capture performance in realistic configurations, not theoretical models
  • Equip professionals with data to help them choose high-performance, buildable solutions

 

The result is a comparative reference built on a solid benchmark: a bare GLT + plywood assembly that returned AIIC/IIC 26, ASTC/STC 31, and HIIC 24. Unlike many overly permissive laboratory environments, FPInnovations’ conditions are intentionally aligned with real-world performance, increasing reliability when transferring results to the field.

 

Inside the Study: What the Data Reveals

 

The study’s strength lies in its side-by-side comparison of more than 40 assemblies, all constructed on the same GLT platform. This consistent baseline allows for a meaningful evaluation of product types, layer combinations, mass additions, fastening methods, and resilient interlayers.

 

Across the dataset, several insights emerge:

 

1. Low-Frequency Sensitivity

 

Mass timber’s inherent lightweight structure makes it especially responsive to low-frequency energy. This study highlights the frequencies that tend to act as limiting factors in achieving higher ratings on GLT.

 

2. Structural Connectivity Matters

 

Continuous elements—joists, sheathing, connectors—play a significant role in the pathways sound can take. Even small detailing changes can influence performance drastically.

 

3. Buildability Is Non-Negotiable

 

One of the core strengths of this study is that all assemblies were designed with realistic construction practices in mind. This helps ensure that high-performing assemblies are not only effective, but also feasible at scale.

 

4. A Foundation for Future Development

 

With over 300 mass-timber-specific tests already completed over the last decade, this study adds an essential new dataset to the growing body of knowledge surrounding mass timber acoustics.

 

Flanking Transmission: A Critical Piece of the Puzzle

 

Beyond direct transmission, the study reinforces the importance of understanding flanking transmission (Kij)—a theme increasingly central to mass timber acoustics research. Lightweight structures, high connectivity, and complex junction geometry make wood buildings more susceptible to flanking than traditional systems.

 

AcoustiTECH is closely involved in broader initiatives, including HGC’s large-scale Kij study supported by WoodWorks USA, the U.S. Forest Products Laboratory, and UNBC. Together, these research efforts aim to refine best practices and improve predictability in acoustic performance across mass timber typologies.

 

A New Tool for Designers, Engineers, and Developers

 

By bringing clear, comparative data to the industry, this study supports:

  • Architects, who need evidence-based details that preserve aesthetic goals
  • Acoustic engineers, who require consistent benchmarks
  • Developers and owners, who must balance performance, risk, and long-term value
  • Contractors, who benefit from assemblies that are grounded in constructability

 

This joint research effort embodies the best of what mass timber innovation looks like: scientific rigor, collaborative expertise, and a commitment to solving real-world challenges.

 

Accessing the Study

 

Professionals interested in exploring the full results can obtain the comparative study directly through:

 

As mass timber continues to evolve, research initiatives like this one will play an essential role in shaping the next generation of high-performance wood buildings. And with more data than ever before, design teams can move forward with greater clarity, confidence, and acoustic insight.

 

 


Andre Rioux
Co-Owner - Executive Vice-President Marketing - 
Product Marketing & Development - Brand Ambassador
AcoustiTECH