Glass Glossary

Outdoor-Indoor Transmission Class (OITC)


Last Updated: November 23, 2023

OITC rating, calculated according to ASTM E1332, measures the capacity of a window or door to reduce the transmission of exterior noise to the interior of a building across the frequency range of 80 to 4000 HZ. This range is broader than the STC range and includes lower frequencies often associated with external noises like traffic and airplanes. A higher OITC rating indicates superior sound insulation against these types of noises.

For homeowners, OITC ratings are crucial when selecting windows and doors, particularly for those living near high-noise sources. Considerations include:

External Noise Reduction: Higher OITC-rated windows or doors provide better sound insulation against external noise sources like traffic and aircraft.

Location and Noise Levels: Homes near airports, highways, or busy urban centers benefit from higher OITC ratings, while those in quieter neighborhoods may not require the same level of insulation.

Comparing OITC and STC

  • Frequency Range: OITC covers 80 to 4000 Hz, emphasizing lower frequencies associated with external noise sources, while STC focuses on 125 to 4000 Hz, primarily covering human speech frequencies.
  • Noise Source: OITC is more suitable for assessing insulation against external noise (traffic, airplanes), while STC is more relevant for interior noise (conversations, televisions).
  • Application: For homes in noisy environments, OITC may provide a more accurate assessment of a window or door’s effectiveness in blocking outdoor noise, whereas STC might be more relevant in multi-family dwellings or situations where interior noise insulation is a priority.

Both OITC and STC ratings inform your window or door selection based on sound insulation needs. Assess your specific requirements and environment to determine which metric is more applicable for your situation.