Acoustic Terms and Definitions: Impact Isolation Class Rating (IIC)

Impact Isolation Class Rating (IIC) is a rating of impact sound insulation. Impact sound is the sound of impact on a floor surface, like the sound of footsteps on the floor above. It only applies to sound transmitted down through a floor and ceiling. It does not apply to walls.

The International Building Code (IBC) requires that a floor-ceiling separating condominiums, apartments, hotel rooms, or other dwelling units be designed for an IIC of 50 or higher.

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