Speaker
Description
Façade sound insulation is a key feature to reduce sound immission in different kinds of buildings, ranging from standard dwellings to spaces dedicated to entertainment like music clubs, among other activities. In the last decade, since the publication of the standard ISO 16283-3:2016, an important claim has been highlighted: a dodecahedral sound source, as usually employed to measure airborne sound insulation according to the ISO 16283-1 standard, can be used to generate the excitation in the measurement of a whole façade (global method). However, the employment of such source introduces a new degree of freedom concerning the influence of its directivity pattern in high frequencies. It is hence expected that these directional properties could, for example, make us derive different sound insulation values only rotating the source on its axis, keeping its position constant with respect to that of the external microphone. In this paper, to corroborate this hypothesis, we present the results and conclusions arose from an experiment specially designed to evaluate the influence of the rotation of a dodecahedral source in the sound insulation, in a scenario where all the other parameters remain unmodified. The conclusions of our study indicate that, although the influence of the spinning of the source is moderated in terms of Single-Number Quantities (i.e., Dls2m,nT,w), the frequency-dependent sound insulation shows an important variation with respect to the rotation of the source, mostly in frequency bands around 2 kHz. These findings would suggest a limitation of the method if additional conditions are not incorporated.