Investigation of prediction methods for low height noise barrier implementation
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Sound and vibration (MPSOV), MSc
Publicerad
2022
Författare
Eriksson, Patrik
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
In areas where the more common tall noise screens produce an unreasonably large reduction
on the quality of the urban environment, absorbing low height noise screens,
in short LHNSs, can be introduced. Due to the screens relatively low height and
the fact that they benefit from a placement as close to the source as possible, the
visual impact on the environment is small. Furthermore studies have shown them
to be cost effective and produce equal, or in some cases, higher attenuation than
their more traditional counterparts.
However, due to the scale and cost of projects regarding railway infrastructure
there is small room for error. Because of this, the current uncertainties in the
prediction methods are often enough to warrant the usage of other noise reducing
devices even though the LHNS could be viable solution.
To give the Swedish Transport Administration a solid basis on which to perform
calculated estimates an investigation is launched. A literature study shows that to
make good estimations of the sound field from a train screened with a LHNS, a
combination of more traditional methods and numerical simulations are required. It
also shows the importance of an accurate source model including the relative energy
distribution between the sub-sources of a train.
Based on the findings a model utilising the 2.5D boundary element method is
implemented to simulate the pressure field with and without screen for different
train shapes. Geometrical estimations of a X60 commuter train, an empty industrial
wagon and a case without a wagon are studied. The low height noise screen was
modelled after the dimensions of an S-block 250.
The simulations show that a reasonably good fit to measurement data from other
projects can be achieved in third-octave bands. However, in some cases, large deviations
can be noted. Because of this further validations with a designated test setup
is advised before drawing any definitive conclusions. Apart from the identified large
deviations the results calculated here consistently show that a considerable reduction
can be achieved by the implementation of LHNSs and that they warrant further
consideration in future infrastructure projects.
Beskrivning
Ämne/nyckelord
low-height noise screen, train, railway, STA, BEM, 2.5D-Geometry, Nord2000, insertion loss, NRD