As life moves faster and populations increase, noise pollution continues to rise. In buildings near airports, planes flying overhead make it hard to hear anything – teachers talking in classrooms, doctors meeting with patients, business seminars in session, orchestras playing in auditoriums.

Whether it’s a jackhammer outside your window, a busy expressway nearby or planes overhead, noise is more than a nuisance; it has been linked to stress, poor concentration, sleep issues and productivity loss in the workplace.

Use Coverboard to Reduce Sound Transmission
If there was a simple way to reduce sound transmission, why isn’t everybody doing it? Good question. Because at least for roofing professionals, the answer is a no-brainer: Apply coverboard.

Coverboard will add density, and density helps mitigate sound. When you add coverboard to your roofing assembly, you will reduce sound intrusion.

Choose Coverboard That Helps Attain an STC Rating of 60-Plus
Sound Transmission Class (STC) measures how effectively a building material or building assembly blocks airborne sound. It is measured in a specially designed laboratory chamber using test method ASTM E90 with classification through ASTM E413.

STC is a standardized, single-number rating system. The number applied to a tested material reflects its ability to decrease sound transmission. So, the higher the STC number, the better job it does.

Roof assemblies should have a minimum STC rating of 50 where noise is a concern. But to really reduce sound transmission, I would recommend using a roofing system with an STC rating of 60-plus. That is nirvana, and the inside environment will be considerably quieter.

STC Ratings and What You Would Hear

You would be able to hear and understand:

  • 25 = Normal speech
  • 30 = Loud speech

What you would hear and understand becomes increasingly muffled as STC ratings increase:

  • 35 = Loud speech audible but unintelligible
  • 40 = Loud speech audible as murmurs
  • 45 = Loud speech heard but inaudible
  • 50 = Loud sounds heard faintly
  • 60+ = Most sounds do not disturb neighbors – Good soundproofing


OITC And What It Means
While STC measures sound transmission from one room to another, Outdoor Indoor Transmission Class (OITC) measures sound transmission from outside of a building to inside. Because outside noises tend to emit

at lower frequencies, OITC focuses on measuring sounds such as construction vehicles, car horns and airplanes.

Like STC, OITC is a single-number rating. But the OITC rating is generally much lower than the STC rating because it weighs low- to mid-frequency sounds more heavily. OITC offers a secondary assessment, but STC is still the primary rating method to evaluate a material’s sound damping abilities.

LEED v-4.1 Raises the Bar on Acoustic Design
When you reduce sound transmission, the quality of life within a building improves. LEED v-4.1 addresses how important acoustics are to the health of those occupying a building. To meet the latest LEED certification for effective acoustic design, requirements have become more stringent.

Looking into the future, we can imagine that these criteria will continue to tighten as world populations multiply and silence becomes even more golden.

Mitigate Noise and Reinforce Your Roof
Along with mitigating noise, coverboard helps protect insulation, increase wind and fire resistance, enhance thermal performance and more. Watch for additional data in a future blog. In the meantime, stay well and don’t hesitate to contact me for more information.


Contact Brian G. Randall at Brian is the Director of Business and Technical Development for National Gypsum Company, based in Charlotte, N.C. One of the original inventors of Glass Mat Gypsum Panels, he has been an innovator and authority on building sheathing, roofing and building practices since 1980. In addition to serving on many ASTM committees, he has been a member of the three model building codes, the Gypsum Association, Exterior Insulation Manufacturers Association, NRCA, IIBEC and RICOWI. Randall is named on 21 patents for glass-reinforced gypsum board.