Understanding STC and OITC: The Definitive Guide to Acoustic Ratings

When designing commercial spaces, recording studios, or high-end residential properties, controlling noise is paramount. However, evaluating the effectiveness of soundproof windows, doors, and partitions requires understanding specific acoustic metrics—most notably STC and OITC.

What is STC (Sound Transmission Class)?

STC is an integer rating that determines how well a building partition attenuates airborne sound. It is primarily used to evaluate interior walls, ceilings, floors, doors, and interior windows. The higher the STC rating, the better the sound isolation.

• STC 30-35: Loud speech can be heard and understood.
• STC 40-45: Loud speech can be heard but not understood. Normal speech is inaudible.
• STC 50+: Very loud sounds (like musical instruments or shouting) are barely audible. This is the standard for premium acoustic environments.

What is OITC (Outside-Inside Transmission Class)?

While STC is excellent for interior noise (like speech), it falls short when measuring low-frequency exterior noise such as traffic, construction, or aircraft. This is where OITC comes in. OITC places more emphasis on low-frequency sounds, making it the superior metric for exterior windows and facade elements.

Choosing the Right System

At Kiran Slido Craft, our acoustic engineering focuses on both high STC and OITC performance. Our premium soundproof sliding doors and casement windows utilize advanced compression seals, specialized laminated glass, and decoupled frame structures to achieve STC ratings upwards of 50+, ensuring total acoustic isolation regardless of the external environment.