Principles of constructing a short test method for impact sound insulation measurements

The principles of short test methods for impact sound insulation measurements are analyzed and a method is outlined. The method is based on a frequency weighting and measurements of the overall level in the receiving room. The construction of a successful short test method is shown to depend on the basic standards, ISO 140 and ISO 717. The use of reverberation time as such or in calculating absorption causes difficulties when using a reference sound source. It is therefore preferable that comparisons between the basic ISO and short test results are made by using a reference source only. ISO 717 implies a weighting analogue which is generally useful. However, the weighting-based short test method is incapable of estimating the possible differences caused by the shifted reference curve system. Thus the short test results should be compared with those obtained with a specified weighting. To show the generality of the reference curve method, and to realize practical tests, an A-based weighting is introduced and converted to a reference curve. The actual method is constructed on the basis of ISO 140. The method is found to be analogous with the respective short test method for airborne sound insulation, but here the possible errors may be smaller because two additional parameters of the airborne sound case are absent. Finally, the method is applied to a real data set, and is seen to yield reasonably accurate results. The deviations are fairly well within the worst-case errors, calculated for varying absorption in the receiving room.