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dc.contributor.advisorChandler-Wilde, SN-
dc.contributor.authorMorgan, Philip Alan-
dc.descriptionThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 12/11/1999.en_US
dc.description.abstractThe performance of various designs of outdoor noise barrier has been investigated using numerical modelling and full scale experiments. The numerical modelling has been performed using a two-dimensional boundary element method. The model has been extended to allow the efficient simulation of barrier arrangements on ground having two distinct impedance values and cross-sections incorporating cuttings. It has been reported previously that the performance of a plane screen can be enhanced by adding a device to the top of the barrier to induce destructive interference. Full scale modelling and boundary element simulations have been performed on one such commercially available device. It has been shown that, taking the height increase into account, the major contribution to the improved performance is the presence of two diffracting edges rather than any interference effects generated. It is known that the performance of a single barrier is degraded following the introduction of a barrier on the opposite side of a source. Boundary element simulations of such parallel arrangements have been performed. Modifications have been proposed to reduce the over-estimation of multiple reflections within the model, together with a method for converting predictions to the equivalent point source values. Sound absorptive, tilted and median barriers have been shown to be effective in reducing the degradation. A multiple-edge barrier configuration is known to offer improved screening performance over a plane screen. Reported in-situ measurements have suggested the behaviour to be influenced by site geometry. Boundary element calculations have been performed to identify a more efficient variant of the device. The results suggest the addition of an inclined base panel to be most effective. The boundary element model has been used to investigate the effect of shape and surface treatment upon railway noise barriers. The model has been adapted to allow the use of dipole sources characteristic of railway noise. The cross-section of the rolling stock has been shown to affect the performance of rigid barriers. If the upper edges are coincident, the results suggest that simple absorptive barriers provide better screening than tilted designs. The addition of multiple edges further enhances performance.en_US
dc.description.sponsorshipEPSRC; Transport Research Laboratoryen_US
dc.publisherBrunel University, School of Information Systems, Computing and Mathematics-
dc.relation.ispartofSchool of Information Systems, Computing and Mathematics-
dc.subjectAbsorptive barriersen_US
dc.subjectDestructive interferenceen_US
dc.subjectDiffracting edgesen_US
dc.subjectMultiple-edge barrieren_US
dc.subjectInclined base panelen_US
dc.titleBoundary element modelling and full scale measurement of the acoustic performance of outdoor noise barriersen_US
Appears in Collections:Dept of Mathematics Theses
Mathematical Sciences

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