Notes to Table 4.1.8.18.:
5.8.1.4. Detailed Method for Calculating ASTC (1) This Article sets out the detailed method for calculating the ASTC ratings of separating assemblies and adjoining construction referred to in Subclause 5.8.1.2.(2)(b)(i). (2) The sound transmission loss measured in accordance with ASTM E90, “Laboratory Measurement of Airborne Sound Transmission Loss of Building Partitions and Elements”, shall be used in lieu of the sound reduction index required in ISO 15712-1, “Building Acoustics - Estimation of Acoustic Performance of Buildings From the Performance of Elements - Part 1: Airborne Sound Insulation Between Rooms”. (3) The vibration reduction index for the junctions between separating assemblies shall be, (a) determined using the equations presented in Annex E of ISO 15712-1, “Building Acoustics - Estimation of Acoustic Performance of Buildings From the Performance of Elements - Part 1: Airborne Sound Insulation Between Rooms”, or (b) measured in accordance with Parts 1 to 4 of ISO 10848, “Acoustics - Laboratory Measurement of the Flanking Transmission of Airborne and Impact Sound Between Adjoining Rooms”. (4) The normalized flanking level difference shall be measured in accordance with Parts 1 to 4 of ISO 10848, “Acoustics - Laboratory Measurement of the Flanking Transmission of Airborne and Impact Sound Between Adjoining Rooms”. (5) The direct sound reduction index for the separating assembly in situ shall be determined from sound transmission loss in accordance with Clause (a) or (b), depending on the type of construction: (a) for a lightweight separating wall or floor assembly with wood or steel framing, the index shall be taken as equal to the sound transmission loss, without correction, (b) for a heavyweight separating wall or floor assembly of concrete or masonry, the index shall be determined in accordance with the detailed method for structure-borne transmission presented in ISO 15712-1, “Building Acoustics - Estimation of Acoustic Performance of Buildings From the Performance of Elements - Part 1: Airborne Sound Insulation Between Rooms”. (6) The flanking sound reduction index for each flanking path at each edge of the separating assembly shall be determined in accordance with Clause (a), (b) or (c), depending on the type of construction: (a) for a lightweight separating wall or floor assembly with wood or steel framing and connected lightweight flanking assemblies with wood or steel framing, the index shall be taken as equal to the normalized flanking level difference re-normalized for the ASTC field situation in accordance with Annex F of ISO 15712-1, “Building Acoustics - Estimation of Acoustic Performance of Buildings From the Performance of Elements - Part 1: Airborne Sound Insulation Between Rooms”, (b)  for a heavyweight separating wall or floor assembly of concrete or masonry and connected flanking assemblies of concrete or masonry, the index shall be determined in accordance with the detailed method for structure-borne transmission presented in ISO 15712-1, “Building Acoustics - Estimation of Acoustic Performance of Buildings From the Performance of Elements - Part 1: Airborne Sound Insulation Between Rooms”, (c) for a mixture of lightweight framed assemblies and heavyweight concrete or masonry assemblies, the index shall be determined in accordance with Clause (a) or (b). (7) Once the pertinent indices and measurements referred to in Sentences (2) to (6) have been determined based on the type of construction, the apparent sound reduction index shall then be determined in accordance with ISO 15712-1, “Building Acoustics - Estimation of Acoustic Performance of Buildings From the Performance of Elements - Part 1: Airborne Sound Insulation Between Rooms”. (8) The ASTC rating shall be calculated in accordance with ASTM E413, “Classification for Rating Sound Insulation”, using the apparent sound reduction index determined in Sentence (7), which shall be treated as equivalent to the values of apparent sound transmission loss measured in accordance with ASTM E336, “Measurement of Airborne Sound Attenuation between Rooms in Buildings”.