Estimating Impact noise through Cross Laminated Timber floors using the Transfer Matrix Method
Typ
Examensarbete för masterexamen
Program
Sound and vibration (MPSOV), MSc
Publicerad
2021
Författare
Jansson, Linnea
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
In 1994 the Swedish building regulations was updated, allowing tall buildings to be
built with wood as load bearing material. However, the sound protection regulations
was not changed, which meant that wooden buildings would be acoustically evaluated
according to the old standard, which was developed for heavy construction
materials, e.g. concrete.
Light and heavy constructions behave different acoustically. Due to this, wooden
constructions struggles to keep up with the standard’s requirements in low frequencies,
where they are bad at attenuating sound compared to heavy constructions.
In order to start building more with wood, it is necessary to be able to estimate the
acoustical behaviour of wooden constructions - especially in the lower frequencies.
The aim of the thesis is to investigate if the transfer matrix method is suitable when
estimating the impact noise through cross laminated timber (CLT) floors and if it
provides a reliable estimation compared to measured and simulated results.
The transfer matrix method can be used to calculate impact sound trough a stratified
medium. Each layer is expressed with a transfer matrix which is coupled together in
a global transfer matrix. The acoustical parameters on the output side is obtained
by solving the global transfer matrix. The final result is size corrected with the
radiation efficiency factor of a corresponding equivalent baffled plate.
The calculated results are first validated for heavy constructions with measurements
and simulated results from Bastian, a computer program used for e.g. estimating
impact noise through a building element. Then the transfer matrix method is used
to calculate the impact noise through CLT floors, which is compared to measured
and simulated data. The results show that the transfer matrix method is suitable for
estimating the acoustical behaviour of bare CLT floors and multiple layers. It is especially
reliable in lower frequencies but show larger differences in higher frequencies
compared to calculations on heavy constructions.
Beskrivning
Ämne/nyckelord
Impact noise, cross laminated timber, transfer matrix method, finite size correction