Effect of airborne sound on installation noise. Pt.2: Practical application

The noise excitation of buildings by service equipment takes place by both structure-borne and airborne sound. Mostly sound transmission is determined by the structure-borne portion. For some sources, however, the contribution of airborne sound can't be neglected. A typical example is the EMPA-hammer, defined in the swiss standard SIA 181 as a standardized source for the simulation of user noise. If airborne sound contributes substantially, conventional measures for noise reduction based on elastic isolation between source and building won't work properly. In order to develop efficient measures for that kind of excitation, structureborne and airborne sound must be separated and investigated in context with each other. The practical consequences of airborne sound transmission were investigated using water installations (bath tubs, etc.) excited by an EMPAhammer as example. Since the resulting sound level in the installation room can reach up to 100 dB(A), special measures for noise reduction are required. Apart from the description of appropriate measures as e.g. damping of the vibrating surface by coating, the sound generated by the EMPA-hammer is compared with real user noise. Furthermore the measuring results are discussed with respect to basic investigations using a simplified experimental set-up consisting of two parallel plates