Variations in Sound Insulation in Nominally Identical Prefabricated Lightweight Timber Constructions

Abstract

Variations in sound insulation necessitate higher safety margins to the legal requirements, which results in higher production costs. Increased knowledge about variations leads to lowered costs and better sound quality. In-situ measurements of 30 nominally identical apartments of a lightweight timber construction were performed, to assess and quantify the variations in airborne sound reduction and impact sound pressure level. The construction is an industrially prefabricated system of complete volumes. Different sound insulation was found between floor numbers as the apartments on the highest floor achieved significantly better sound insulation. This difference was assumed to be due to the extra weight on lower floors affecting the elastic connections used to structurally connect the apartments. The variation between apartments on the same floor was therefore evaluated using the Root Mean Square Error, resulting in a standard deviation of 0,9 dB and 1,4 dB for the airborne and impact sound insulation, respectively. The measurement variance was subtracted from the total variance. The remaining, unexplainable, variation of 0,8 dB in airborne sound insulation can be attributed to workmanship.