The Total Sound Approach: Solving Acoustical Challenges in Modern Construction

Have you ever been in an airport and couldn’t understand a PA announcement? Out for dinner and can’t keep up a conversation with the person across the table? 

Poor acoustics and the resulting loud noise can drastically affect your life, and it’s not just a matter of missing a gate change or being a bad date; it can affect your health as well.

Research shows that chronic noise exposure can harm the central nervous system and brain. The health implications are significant, with increased risks of stroke, dementia, cognitive decline, neurodevelopmental disorders, depression, and anxiety.¹

Given this impact, acoustics must be an integral part of a building’s design. Despite this, outside factors like controlling costs and tight construction schedules will deprioritize acoustics, often in favor of visual aesthetics and other traditional design imperatives.

The Mass Timber Challenge

Mass timber is known for its visually striking exposed-structure design, but the materials and construction assemblies in these buildings make for unique acoustic challenges, particularly around sound absorption and sound transmission. These challenges must be addressed in the design phase of a project or risk excessive noise later.

Achieving Sound Absorption

Suspended acoustical tile ceiling systems are effective at controlling reverberation, but will hide the mass timber wood structure above. This is an issue because not only is mass timber a more sustainable solution for building construction, but it’s also a valued aesthetic choice, showcasing beautiful wood grain throughout the building’s interior.

Instead of hiding the entire wood grain floor-ceiling with a suspended ceiling system, specialty ceiling products, like a baffles array, offer both aesthetic cohesion and acoustic absorption for standout ceiling features that enhance rather than obscure the main draw of mass timber.

Mitigating Sound Transmission

Without a full ceiling system in place for acoustic control, some key issues would need to be addressed for meeting sound transmission class (STC) and impact isolation class (IIC) requirements without compromising aesthetics. Suspended drywall ceilings can provide the necessary STC/IIC ratings, but, again, covering a mass timber building in a ceiling system would not be an ideal solution that achieves both aesthetics and performance. 

 To effectively reduce airborne and impact sound transmission in mass timber buildings, turn your focus to flooring solutions. Adding mass to the floor, in the form of poured concrete, can improve STC, but it will have little effect on IIC. Additionally, the weight of traditional poured concrete can create structural issues, and its long curing times can delay construction schedules.

Instead, opt for a poured gypsum underlayment, along with decoupling through sound mats and resilient layers.  Poured gypsum cures faster than traditional concrete and enables the floor assembly to achieve high STC and IIC ratings with the incorporation of a sound mat between the gypsum and subfloor.

Making Sense of Acoustic Data

So much of acoustical performance is defined in data, numbers, and ratings. Understanding acoustic metrics and data is critical for accurate specifications, but these numbers rarely resonate with clients and can make design decisions challenging. What’s more, there are misconceptions about acoustic data that lead to confusion and misinformed specifications.

NRC vs. Array NRC

One area where confusion arises is the sound absorption of ceiling baffles. The industry hasn't had a consistent way of calculating noise reduction coefficient (NRC) for baffle arrays until the standardization of a value known as Array NRC, as defined in ASTM C423.

Array NRC is intended to provide a similar value to the more common NRC ratings of ceiling panels. But since array NRC hasn't made its way into most manufacturers’ literature, there are still a lot of misleading claims due to alternate, non-standardized methods of calculating NRC for baffles that can artificially inflate their acoustic ratings. 

The new standard calculation of Array NRC the total absorption of the baffles array (in Sabins) divided by the total area covered by the array, and the spacing of the individual baffles has a significant influence on the Array NRC. For example, a 2” x 10” baffle system may achieve an Array NRC of 1.3 at 6” on-center spacing but drops to 0.9 when spacing at 12” on-center.  

Misunderstanding Sound Transmission

Wall construction details matter more than most realize, and while people often interpret drywall as the most significant influencer of STC, there are often other factors at play, such as the framing system. 

This misunderstanding can have a drastic effect on the STC ratings of a wall system. Differences in wallboard types may amount to a 1-to-3 point shift in a wall STC, but framing system spacing can cause a difference of 10 points or more.  

Another common misconception is adding resilient channels over existing drywall to improve STC. When the resilient channels are “sandwiched” between the panel layers, this does very little to increase STC. In order for resilient channels to provide real STC benefit, they need to be attached directly to framing with drywall layers attached to those channels. 

Start Thinking Like an Acoustical Consultant

All of these acoustic data points and considerations may seem to be a lot to take in, but many projects cannot afford the luxury of having an acoustical consultant. This is why it’s important to embed acoustic principles from the start of a project as a design imperative. 

When you start thinking like an acoustical consultant early, it can help answer questions in the pre-design phase rather than further down the line when changes cannot be made easily.

Here are three ways to embed acoustic thinking into your design process:

Step 1: Identify project types and utilize design guides

Luckily, there's a design guide for just about every vertical and application you may be designing for; the Facility Guidelines Institute™ helps determine requirements for healthcare facilities, and the Acoustical Society of America has developed a guide for educational facilities.

These guides are your starting point for getting acoustics right. 

Step 2: Space planning that accounts for noisy and quiet zones 

Consider the activities planned for each space. Identify sound-critical spaces and ask yourself, “Where do we need quiet? Where is speech intelligibility or privacy essential?” 

In short, keep loud and quiet areas separate. If you're designing a sound-sensitive multimedia conference space and you're planning to put it right next to a large mechanical room, you will need high-STC construction, which can be both complex and costly. 

Step 3: Use digital tools that help bring data values to life

Digital planning tools can be a difference maker in making the most of a space’s acoustic performance. USG offers tools like Ceiling Technix™ and Assembly Builder™, and resources like Design Studio to help architects and designers meet various acoustic requirements, while the Virtual Acoustic Experience™ immerses users in a virtual environment that helps simulate how different products affect the built environment. 

The USG Solution

Acoustics should matter to your materials manufacturer. Partner with USG to balance budget, aesthetics, and acoustic performance from the start. Your project becomes our project, incorporating acoustic performance considerations as a critical design component rather than an afterthought.

Watch the full Total Sound series on YouTube for expert insights from USG’s Principal Researcher in Acoustics, Andrew Schmidt.

Source(s)

1. https://www.sciencedirect.com/science/article/pii/S0160412022002331?itid=lk_inline_enhanced-template#f0005