STC vs OITC Ratings for Window Glass Packages
Window glass packages can vary dramatically in how well they reduce outside noise. Two common ratings are used when comparing sound performance: STC and OITC. STC is more commonly associated with mid-to-high frequency sound, while OITC gives more weight to lower-frequency outdoor noise such as traffic, aircraft, trucks, and heavy equipment. Ten decibles offers about a 50% reduction in loudness. Fifteen Decibles brings 63% sound reduction. Twenty decibles is a 75% reduction in loudness.
STC and OITC rating comparison for common residential window glass packages.
Dallas Windows Replacement Window Sound Rating Chart
| # | Glass Package | Typical Glass Configuration | STC Range | OITC Range | Typical Use and Noise Sources |
|---|---|---|---|---|---|
| 1 | Single Pane Glass | 3/32" annealed glass | 18–21 | 17–20 | Old single paned windows, circa 1900 to 1970s. |
| 2 | Standard Dual Pane | 3/32" glass / 1/4" air space / 3/32" glass, approximately 7/16" overall insulated glass thickness | 23–25 | 20–22 | Standard builders grade windows. Usually aluminum, circa 1980s to 2008. |
| 3 | Double Strength Dual Pane Double Strength Glass
1/8" glass with 1/2" spacer. |
1/8" glass / insulated air space w/ Argon Gas / 1/8" glass. 3/4" overall insulated glass thickness | 27–30 | 23–25 | Modern thicker insulated glass from the 2008 and most modern high quality replacement windows. Many builders grade vinyl windows have thicker insulated glass units as well. Most economy windows utilize 3/32" (single strength) glass. |
| 4 | Triple Pane Basic Glass Package Three single strength glass @ 3/32" and two 1/4" spacer bars |
Three thin glass lites with two smaller spacer bar cavities, 3/4" overall insulated glass thickness | 31–33 | 25–27 | Lower U values. Modest improvement to sound abatement over double pane. |
| 5 | Dissimilar Glass | 3/16" glass with 1/8" glass, 3/4" overall insulated glass thickness, 7/16" spacer | 35–37 | 28–30 | Available upgrade to modern windows. Helps disrupt more frequencies than equal-thickness glass. Also known as offset glass. |
| 6 | Laminated Exterior Lite | 0.030" (3/100") laminated exterior lite over 1/8" interior glass, approximately 3/4" overall insulated glass thickness | 39–41 | 31–33 | Major acoustic upgrade. Excellent for aircraft, freeway noise, traffic, barking dogs, and sharp exterior sounds. |
| 7 | Laminated Exterior Lite with Thicker PVB | 0.090" (9/100") laminated exterior lite over 1/8" interior glass, approximately 3/4" overall insulated glass thickness | 43–45 | 34–36 | Maximum industry improvement to noise abatement in common modern residential insulated glass packages. This is the top tier without using two windows stacked together. |
What Is the Difference Between STC and OITC?
STC: Sound Transmission Class
STC, or Sound Transmission Class, is a laboratory rating commonly used to compare how well a wall, window, door, or glass package reduces sound transmission. STC is most useful for comparing mid-to-high frequency sounds such as voices, televisions, alarms, and general indoor or outdoor noise.
OITC: Outdoor-Indoor Transmission Class
OITC, or Outdoor-Indoor Transmission Class, gives more weight to lower-frequency outdoor sounds. This makes OITC especially useful when comparing windows for traffic noise, aircraft noise, truck rumble, construction equipment, and other low-frequency outdoor noise sources.
Best Window Glass Packages for Noise Reduction
Triple pane glass may improve energy performance and lower U values, but it does not always outperform dissimilar or laminated glass for noise reduction. For traffic, aircraft, and freeway noise, laminated exterior glass packages generally offer stronger acoustic performance.