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The 2.5-dimensional equivalent sources method for directly exposed and shielded urban canyons

Maarten Hornikx (Institutionen för bygg- och miljöteknik, Teknisk akustik, Vibroakustik) ; Jens Forssén (Institutionen för bygg- och miljöteknik, Teknisk akustik, Vibroakustik)
Journal of the Acoustical Society of America (0001-4966). Vol. 122 (2007), 5, p. 2532-2541.
[Artikel, refereegranskad vetenskaplig]

When a domain in outdoor acoustics is invariant in one direction, an inverse Fourier transform can be used to transform solutions of the two-dimensional Helmholtz equation to a solution of the three-dimensional Helmholtz equation for arbitrary source and observer positions, thereby reducing the computational costs. This previously published approach [D. Duhamel, J. Sound Vib. 197, 547–571 (1996)] is called a 2.5-dimensional method and has here been extended to the urban geometry of parallel canyons, thereby using the equivalent sources method to generate the two-dimensional solutions. No atmospheric effects are considered. To keep the error arising from the transform small, two-dimensional solutions with a very fine frequency resolution are necessary due to the multiple reflections in the canyons. Using the transform, the solution for an incoherent line source can be obtained much more efficiently than by using the three-dimensional solution. It is shown that the use of a coherent line source for shielded urban canyon observer positions leads mostly to an overprediction of levels and can yield erroneous results for noise abatement schemes. Moreover, the importance of multiple façade reflections in shielded urban areas is emphasized by vehicle pass-by calculations, where cases with absorptive and diffusive surfaces have been modeled.



Denna post skapades 2008-10-27. Senast ändrad 2014-10-27.
CPL Pubid: 76357

 

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Institutioner (Chalmers)

Institutionen för bygg- och miljöteknik, Teknisk akustik, Vibroakustik

Ämnesområden

Akustik

Chalmers infrastruktur