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Noise Reduction Coefficient (NRC) is a measure of sound absorption. This is an important consideration for controlling acoustics within a confined area. Tests are conducted according to ASTM C423.

• ASTM C423: Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method

Ceiling Attenuation Class (CAC) applies to the sound attenuation of acoustical ceilings with a shared plenum between horizontally adjacent spaces. Tests are conducted per ASTM E1414 and classified per ASTM E413.

• ASTM E1414: Standard Test Method for Airborne Sound Attenuation Between Rooms Sharing a Common Ceiling Plenum

• ASTM E413: Classification for Rating Sound Insulation

Sound Transmission Class (STC) is a widely used rating of sound attenuation performance of wall and floor systems. Laboratory tests are conducted per ASTM E90 and classified per ASTM E413.

• ASTM E90: Standard Test Method for Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements

• ASTM E413: Classification for Rating Sound Insulation

Impact Insulation Class (IIC) is a numerical evaluation of a floor/ceiling assembly’s effectiveness in retarding the transmission of impact sound, also determined from laboratory testing. Laboratory tests are conducted according to ASTM E492 and classified per ASTM E989.

• ASTM E492: Standard Test Method for Laboratory Measurement of Impact Sound Transmission Through Floor-Ceiling Assemblies Using the Tapping Machine

• ASTM E989: Standard Classification for Determination of Impact Insulation Class (IIC)