OITC (ASTM E1332) weights low frequencies from 80 to 4,000 Hz more heavily than STC does, because traffic, aircraft and trains carry most of their energy in the bass. A window with STC 35 might have an OITC of only 28.
- Use OITC to compare windows, doors and facades near roads, railways and airports.
- Laminated glass and wide air gaps between panes improve OITC most.
- Seal around frames: a small gap undoes an expensive window.
See windows and STC.