Abstract
This second part, of a two part paper, presents and analyses the results of an Inter-Laboratory Test (ILT) for a heavy single leaf wall. Significant differences were found in the measured sound reduction index (SRI) for the participating laboratories. These differences were not caused by the measurement technique. During the ILT the damping of the test wall in terms of the total loss factor in each laboratory was measured in addition to other measurements.
The damping of the test element was controlled by the design of the transmission suite supporting walls. It is shown that the results of the damping measurements can be used to reduce the variations of SRI. Other influences of the transmission suite such as flanking transmission are also discussed. It is found that the principle reason for the differences in the sound reduction index is the type of construction of the transmission suite.
From this study suggestions for the improvement in the reliability of sound insulation measurements are given, which could provide improvements in standardisation.