Improving the accuracy of vibration reduction index measurements: Assessing and correcting parasitic airborne noise effects

The vibration reduction index K ij , measured in accordance with ISO 10848, is used to assess the attenuation of vibration transmissions at junctions between structural elements. In particular, it is used to compare the performance of different junctions or as input data for predictive calculations in the ISO 12354 standards series. However, this measurement can be affected by parasitic airborne noise generated by the excitation source and acoustic radiation from the excited wall, leading to an underestimation of K ij , particularly for high-performance junctions such as those incorporating resilient strips. This article presents the results of numerical simulations based on the finite element method and experimental measurements carried out on two CLT mock-ups in two laboratories, one in Italy and the other in Belgium. These analyses highlight the influence of parasitic airborne noise on Kij measurements and underline the importance of minimising it as much as possible during testing to ensure the reliability of the values obtained. If this is not possible, a correction based on the subtraction of the contribution of unwanted airborne noise can be applied to improve the accuracy of the results. The conclusions of this study are generalizable to any type of construction element and also to in situ measurements. The issue of incorporating parasitic airborne transmission into the predictive calculations of ISO 12354 standards is therefore raised, particularly when the construction elements of junctions incorporating a resilient strip are not combined with a lining or floating screed.