Investigation of alternative methods for measuring and evaluating airborne sound insulation

Abstract

The reproducibility of airborne noise insulation testing is poor, as documented by various interlaboratory studies. This is compounded by the definition of Sound Transmission Class (STC), the dominant single-number rating used in North America, which over-emphasizes the wall performance at and around the 125 Hz third-octave band. Small variations in performance at these frequencies can result in substantial changes in STC rating. To address these concerns, changes to both the measurement method and the single number ratings may be appropriate. For the former, the authors have begun an investigation of measuring the vibro-acoustic characteristics of walls, including measuring the vibration on the surfaces of the separating assembly and the flanking assemblies. This may result in increased precision of sound insulation measurements. For the latter issue, the authors have performed statistical evaluation of published wall sound insulation tests to clarify the effects of idiosyncrasies in the definition of STC and investigated whether different rating methods may better describe the performance of wall assemblies.