New Investigations into Measurement Techniques Using the Pendulous Hammer to Assess Acoustic Insulation in Relation to User-Generated Noise in Residential Buildings

With the release of the revised version of the Swiss standard SIA 181:2006 "Protection Against Noise in Buildings", a measurement technique was introduced for simulating user-generated noise in bathtubs, shower cubicles, wash basins etc. employing a pendulous hammer. Despite the undoubted advantages of the measurement method, over the past few years questions have increasingly been raised regarding various issues involved in its use. The characteristics of the pendulous hammer are insufficiently well specified in the standard and a procedure specifying a periodic check of the instrument is lacking. The measurement method itself is described in inadequate detail, so that (for example) depending on the choice of the excitation, potentially very diff erent results may be obtained. In addition, no information is given regarding the measurement uncertainty. The standard gives level corrections for diff erent excitation scenarios. This allows a comparison of the diff erence between the level of the original noise and that generated by the pendulous hammer. The validity of these level corrections is now, to a certain extent, being challenged. In addition, it has been suggested that – depending on the constructional details - the airborne noise emitted by acoustic radiation from the component under investigation is excessive, thereby potentially falsifying the measured values. These issues have been investigated by Empa and, based on a comprehensive set of laboratory and field measurements, clarified. Measurement protocols are given for various components, and the measurement uncertainty has been evaluated. The eff ect of airborne noise has been shown to be acceptable for tests conducted in accordance with the SIA 181 standard. Sufficient measurement data is now available to allow the level corrections to be determined. Finally, specifications for the pendulous hammer itself have been formulated.