With the increasing construction of Cross Laminated Timber (CLT) buildings, the demand for enhanced acoustic performance is also rising. To improve the sound insulation, resilient interlayers are inserted in the structure, which decreases the flanking transmission. These interlayers are generally placed between the floor and the wall and are under a static load, which depends on the relative floor. Interlayers are usually viscoelastic materials with non-linear behaviour. This is why the vibroacoustic behaviour under different loading conditions is investigated in this paper. Through a fullscale mockup, the vibration reduction index Kij of some resilient material with different elastic modulus is measured by placing various static loads over the junction to evaluate different performances. The results reveal significant differences depending on the load applied to the junction. In particular, in the mid-high frequencies, the higher the load, the lower the Kij due to the increase in the dynamic stiffness of the resilient layer in the compression. This supports the importance of choosing the proper resilient material in the design step and carrying out laboratory measurements of Kij with the test conditions as close as possible to the actual conditions of use.