An analytic secondary source model of edge diffraction impulse responses

Citation
Up. Svensson et al., An analytic secondary source model of edge diffraction impulse responses, J ACOUST SO, 106(5), 1999, pp. 2331-2344
Citations number
20
Categorie Soggetti
Multidisciplinary,"Optics & Acoustics
Journal title
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
ISSN journal
00014966 → ACNP
Volume
106
Issue
5
Year of publication
1999
Pages
2331 - 2344
Database
ISI
SICI code
0001-4966(199911)106:5<2331:AASSMO>2.0.ZU;2-E
Abstract
A new impulse-response model for the edge diffraction from finite rigid or soft wedges is presented which is based on the exact Biot-Tolstoy solution. The new model is an extension of the work by Medwin et al. [H. Medwin et a l., J. Acoust. Sec. Am. 72, 1005-1013 (1982)], in that the concept of secon dary edge sources is used. It is shown that analytical directivity function s for such edge sources can be derived and that they give the correct solut ion for the infinite wedge. These functions support the assumption for the first-order diffraction model suggested by Medwin et al. that the contribut ions to the impulse response from the two sides around the apex point are e xactly identical. The analytical functions also indicate that Medwin's seco nd-order diffraction model contains approximations which, however, might be of minor importance for most geometries. Access to analytical directivity functions makes it possible to derive explicit expressions for the first- a nd even second-order diffraction for certain geometries. An example of this is axisymmetric scattering from a thin circular rigid or soft disc, for wh ich the new model gives first-order diffraction results within 0.20 dB of p ublished reference frequency-domain results, and the second-order diffracti on results also agree well with the reference results. Scattering from a re ctangular plate is studied as well, and comparisons with published numerica l results show that the new model gives accurate results. It is shown that the directivity functions can lead to efficient and accurate numerical impl ementations for first- and second-order diffraction. (C) 1999 Acoustical So ciety of America. [S0001-4966(99)02111-6].