10.58  impact insulation class. Single-number rating of impact sound insulation derived by fitting a reference rating curve to the normalized impact sound pressure level values measured for the 16 contiguous one-third octave frequency bands with nominal midband frequencies of 100 Hz to 3150 Hz, inclusive, by a standard method described in ASTM E989. Abbreviation, IIC.

Annotation              A similar field measurement in existing buildings, often subject to flanking transmission, is made with impact sound values obtained via ASTM E1013, rated according to ASTM E989 and named the “apparent impact insulation class,” abbreviation AIIC.

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