In the framework of building acoustics design, sound propagation between rooms is a major
factor in determining the acoustic insulation levels. Acoustic waves can be directly transmitted
through common perimetral surfaces or propagate through indirect transmission paths
via the building’s structure.
These indirect transmission paths are the reason why acoustic waves can travel between
seemingly unconnected far regions of buildings. The amount of energy the acoustic wave
loses when it propagates though a structural junction is quantified with the sound reduction
index of that propagation path. In order to determine these indexes, the vibration reduction
index of the path between two structural elements that are connected by a structural junction
is required. This vibration reduction index is an energetic measure of how different the
average displacement values of those two regions are when the structure is oscillating at a
determined frequency.
Current european regulations have expressions to estimate the vibration reduction index
of geometrically simple three-dimensional junctions with extrusion symmetry. In reality,
such structures are more complex. Structural junctions are usually delimited by other
surfaces and elements that cannot be included in an extrusion symmetry. Existing tables
and formulas do not take into account how the geometrical complexity of a 3D environment
will affect the vibration transmission between two of its parts.
This project will analyse how this geometrical complexity modifies the vibration transmission
indexes. A set of three-dimensional cases will be defined and simulated with finite
element methods, obtaining the vibration reduction indexes for those specific scenarios.
These will be compared with the vibration transmission index of the simplified (extrusion
symmetry) version of those cases, which the codes can estimate, in order to analyse whether
complete three-dimensional geometries entail a significant difference in the vibratory behaviour.
