Calculation of flanking sound transmission according to ISO 15712-1—Comparison between the simplified and the detailed method

Abstract

The 2015 edition of the National Building Code of Canada (NBCC) specifies sound insulation requirements between dwelling units in terms of Apparent Sound Transmission Class (ASTC). The ASTC includes both the direct sound transmission through the separating element between adjacent rooms as well as the sound transmission via flanking paths. One of the ways to establish compliance with the NBCC involves a calculation procedure based on ISO 15712-1, in which the flanking sound transmission is predicted from the measured sound transmission through individual building elements combined with the attenuation at their junction. The calculation can be performed in third-octave bands (“Detailed Method”) or using single-number ratings such as the STC (“Simplified Method”). This presentation will describe the two calculation procedures, before focusing on the differences between. In extended studies at the National Research Council Canada, it was found that the simplified method sometimes leads to misleading results. An alternative method for calculating the ASTC of walls with linings was proposed, which ensures that the simplified method yields more conservative results than the detailed method. To achieve the best possible estimate of the sound insulation performance of buildings systems with linings, the detailed method should be used.