Division
of Engineering acoustics, Lund University,
Lund,
Sweden
Lightweight constructions made of timber
material have a number of advantages; they are cost effective and demand
relatively short production duration. One of the main drawbacks of lightweight
structures is related to sound transmission. The differences in weight,
density, stiffness and repartition compared to traditional materials have
repercussions on how the sound propagates in the rooms and in the structures
themselves. Sound transmission becomes an increasing nuisance. In order to be
able to reduce the sound transmission, a better understanding of how the sound
propagates through a real wood cross junction is needed. A series of in-situ
measurements using a taping machine and arrays of accelerometers have been
performed on a wooden frame building in Limnologen, Sweden. The multi-family
house has seven storeys and contains 34 apartments. While the ground floor is
cast in concrete, all the seven floors are made of wood, what makes this
building a perfect object of study for wood building elements. In particular,
the connections of the floor structures between two neighboring apartments have
been focused on, since they transfer the horizontal forces in the building.
A previous work had already be
presented, with the first measurements results. In the original work, we
focused solely on the propagation of sound and vibration from one room on the
first floor to the adjacent room on the same floor and to the two rooms above.
Here, we extend the investigation further by comparing the former results to
the transmission taking place between the fourth and fifth floors. As it was
expected, we have found strong similarities between both cases due to similar
floor plans. However, we could also observe significant particularities between
the former and the latter results. It appears for example that along certain
paths, the impact sound propagates much better in higher stories than it does
in lower ones. All the results are interpreted, and the results compared with
each other, in order to try to provide an explanation of the observed
differences. For this, the structure of the whole building has been taken into
account instead of just the structure of the concerned rooms. For example, it
appears that the structure elements are under much more stress for the lower
floors, due to the accumulated weight of the floors above, and that this load
might impact the response of the building elements to impact vibration
propagating horizontally and vertically through the structure elements.