Over the years it has been found that high performance lightweight structures under test in the laboratory approached a limiting sound reduction index that was less than expected.This implied the presence of flanking transmission, which was not in compliance with ISO 1110 Part I, and so an investigation of the problem was necessary.Considering firstly the Horizontal Test Suite used for testing partitions; the original plan is shown in Fig. l.The 630 on concrete dividing wall is vibration isolated from the two rooms.The aperture perimeter was lined with 50 mm thick timber to provide easy fixing of partitions.When the

INVESTIGATION OF FLANKING TRANSMISSION IN THE HORIZONTAL AND VERTICAL TEST SUITES AT BRITISH GYPSUM