Accession Number : ADA122023


Title :   Acoustic Propagation and Barrier Diffraction Over an Impedance Plane.


Descriptive Note : Doctoral thesis,


Corporate Author : PENNSYLVANIA STATE UNIV UNIVERSITY PARK APPLIED RESEARCH LAB


Personal Author(s) : Nobile,Matthew A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a122023.pdf


Report Date : 13 Oct 1982


Pagination or Media Count : 217


Abstract : The primary objective of this study was to derive a more exact solution to the problem of acoustic point-source propagation over a locally-reacting, impedance or ground plane. This objective was met with the derivation of an asymptotic series solution. One of the most important features of this solution is that higher-order terms can be calculated from preceding terms in the series by the use of recursion formulae, also derived here. Comparing data predicted from this solution with that from a numerical integration of the exact expression showed the asymptotic series to be extremely accurate, even for very low values of the parameter kR. As expected, the plane wave solution often showed major deviations from the exact integral solution. A secondary goal was to incorporate the new propagation solution into a barrier model so that ground reflections in addition to edge diffraction could be accounted for. Only the first term in the asymptotic ground propagation solution was used for this purpose, as it was shown to be sufficiently accurate for many practical cases. Thus, an Edge-Plus-Images barrier diffraction model was developed in the second phase of this study. The results of preliminary sensitivity tests reported here are very encouraging, and indicate that the barrier model should afford a higher degree of accuracy than available with similar models employing the plane wave reflection coefficient.


Descriptors :   *ACOUSTIC WAVES , *NUMERICAL ANALYSIS , *WAVE PROPAGATION , *SOUND TRANSMISSION , *ACOUSTIC IMPEDANCE , THESES , DIFFRACTION , COEFFICIENTS , NUMERICAL INTEGRATION , ASYMPTOTIC SERIES , RECURSIVE FUNCTIONS , BARRIERS , DIFFERENTIAL EQUATIONS , GEOMETRY , PLANE WAVES , FORMULAS(MATHEMATICS)


Subject Categories : Theoretical Mathematics
      Acoustics
      Radiofrequency Wave Propagation


Distribution Statement : APPROVED FOR PUBLIC RELEASE