Edinburgh Napier University

  Resilient bars provide cheap, effective sound insulation. They are increasingly popular
in timber floor/ceiling assemblies in the UK following the upgrading of Building
Regulations requirements. However, the behaviour mechanisms providing resilient bars
with their insulating properties are not well understood. The effects of specific detailed
features on their performance are assumed or estimated empirically. Myths relating to
property-performance correlation prevail among various product manufacturers.
Previous experimental studies revealed either overall effect or only covered the stiffness
in the vertical direction. Spring and rod models used elsewhere also failed to predict
three-dimensional, asymmetrical facets of resilient bar behaviour.
This research investigated the influence of various three-dimensional resilient bar
features through examining hypotheses: resilient bars act as springs (either vertical,
bending, cantilever or spring hinge), or stiffeners. As these hypotheses are associated
with certain material and geometrical features, the results revealed each's influence and
relative importance. Three types of test were designed: vibration transmission, apparent
stiffness and modal tests. Two representative but distinctly different resilient bar
products were chosen as test subjects, which covered the features of interest and
involved controversies. Vibration transmission tests were conducted on a series of
configurations based on small-scale structures, which could not only demonstrate
overall performance but allow detailed parametric investigations. Apparent stiffness
tests on small samples enable isolation of spring effects so that their individual
contribution could be evaluated. Modal tests revealed how resilient bars modified the
vibration modes of the attached plate. By synthesizing the data from the above three
angles together with data in the literature, the influence of key features was inferred and
evaluated. Mass-spring-mass modelling and statistical energy analysis were carried oout
which enhanced understanding of the system's behaviour.
The findings led to an optimised resilient bar design and a patentable acoustic hanger
system. The latter was prototyped and tested on a floor/ceiling assembly. The results
showed that it was more advantageous than current resilient bar systems.