Determination in the field of structure-borne sound source strength of building service equipment – A pilot study with inter-laboratory comparisons and a proposal for a Nordtest method (NT TR 616)

Abstract

A pilot project with an inter-laboratory comparison (round robin) has been performed, where a modified heavy duty washing machine has been circulated for tests among 7 laboratories. The main goal of this pilot project was to find out whether a simple substitution method could be applied to determine the structure-borne sound source strength of typical building service equipments. The vibration levels of a test floor, measured when a machine operates on this floor, are compared to the vibration levels obtained on the same floor when the standardized tapping machine (ISO 140-7) operates. These vibration level differences may be used to estimate the actual machine force and the characteristic power according to prEN 12354-5. That standard also describes how sound pressure levels in a nearby room may be deduced from the measured data. The vibration level differences are assumed to correspond to sound pressure level differences obtained with measurements according to ISO 140-8, but this has not been validated. If they are found to correspond, they can be used to predict reduction of impact sound in nearby rooms according to EN 12354 part 2 in the same way as for floorings on top of a heavy slab. Some tests were also performed in order to enable comparisons to sound power obtained by the draft standard prEN 15657-1, where the source strength is determined by a reception plate method. However, it was not possible to determine the structural reverberation time and point mobilities of the slabs, thus that comparison could not be completed.