The investigation began by modelling the major processes involved with measurement in the standardised test setup. These include, in particular, the excitation of a floor base construction using a hammering system, the diffusion of energy through the floor base as well as the sound radiation from the floor base. For the overall process, observations are made both with and without floor coverings, in order to provide insight into the various effects of the floor coverings. Amongst other tools, operational vibration analysis is used here.
Based on these findings, a compact method for the determination of impact sound reduction for lightweight covered floors can be developed. For this, it is extremely important that the receiving structure is reproducible in such as way as to enable standardisation. Furthermore, tests are carried out in order to establish whether the improvement values from board-shaped floor coverings on scaled-down constructions can be determined and which physical limitations exist for this.
The developed compact method for the determination of impact sound reduction is tested on real floor coverings and the results are compared to those achieved through standardised measuring procedures. During these measurements, diverse floor coverings are used in order to vary the impact sound reduction to such an extent that possible method limitations become evident. A draft standard is produced and incorporated into the standardisation process.
In addition, investigations are made concerning the feasibility of determining the laboratory value of the impact sound pressure level of wooden floor bases using a scale model. The output emitted by the scale model is calculated using the velocity of the lower surface and the radiation factor of the structurally identical large floor. The velocity can be deduced from measurements taken on a reduced scale, provided the basic characteristics of the original construction are correctly reproduced in the compact test construction. For these models, clear project rules are required. Very little is currently known concerning the radiation factor of timber joist floors. Therefore, a databank for the radiation factors of timber joist floors will be compiled during the course of the project. For this purpose, intensity measurement technology and a laser scanning vibrometer are used, in order to determine the radiation factors of wooden floor bases in real buildings. As the impact sound pressure levels of the real buildings are also determined, the difference between the sound pressure levels and the sound intensity-based sound levels in the receiving area enables conclusions to be drawn concerning flank transfer.
The use of vibration analysis on laminate floor coverings on the compact test rig for solid floors enabled the implementation of models which depict the vibration behaviour of the coverings. With the help of electromechanical analogies, the laminate coverings being tested can be modelled as a mass-spring system. Such a system is characterised by a typical resonance characteristic in its mobility. The mobility depicts the relationship of the applied force and the resulting vibration velocity at the discharge point. Figure 1 shows ten entry mobility values measured on laminate. The mobility of an ideal spring is depicted in red whilst that of an ideal mass is shown in blue. A series connection of these elements, in combination with a resistance term, results in the mobility progression shown in black, which clearly reflects the vibration behaviour of the tested laminate coverings.