title: Finding optimal geometries for noise barrier tops using scaled experiments.
abstract: Scaled acoustic laboratory experiments are used to develop a methodology for obtaining the acoustic characteristics of different barrier top designs and for identifying geometries that may have advantages over the traditional thin vertical screen. The idea is to use a short impulsive spherical sound pulse possessing a broad frequency spectrum. If the duration of the pulse is sufficiently short, the entire primary signal, which travels by the shortest direct route diffracting at the top of the barrier, arrives at the receiver much earlier than any secondary signals reflected from the surroundings. Secondary signals may therefore be ignored and only the information from the primary signal can be analyzed. When the typical frequency band of the sound pulse is about an order of magnitude higher than typical traffic noise spectra, then scaled acoustic modeling using the same scaling factor for lengths and distances is possible. The results of such experiments are reported here for barriers with six different geometries. Using spectral analysis, insertion losses as functions of frequency were calculated for different source-receiver positions and barrier tops. The results were then rescaled for full-size traffic barriers and, using a typical traffic noise spectrum, single number ratings of barrier performance were obtained.
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: Sergey I
authors.initials: SI
authors.lastname: Voropayev
authors.affiliation: Department of Mathematics, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Ovenden
authors.affiliation: Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA.
authors.forename: Harindra J S
authors.initials: HJ
authors.lastname: Fernando
authors.affiliation: Illingworth-Rodkin Inc., 1 Willowbrook Court, Suite 120, Petaluma, California 94954, USA.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Donovan