Index of content:
Volume 120, Issue 2, August 2006
- AEROACOUSTICS, ATMOSPHERIC SOUND 
On the modeling of sound propagation over multi-impedance discontinuities using a semiempirical diffraction formulation120(2006); http://dx.doi.org/10.1121/1.2216905View Description Hide Description
Several approximate extensions of the semi-empirical De Jong model [De Jong et al., J. Sound and Vib.86, 23–46 (1983)] are considered for the prediction of sound propagation over multiple impedance discontinuities. A limitation in the original formulation of the De Jong model is highlighted and a modified form that overcomes this limitation is derived based on reciprocity. This leads to the development of a model for multiple impedance discontinuities that can be used for the investigation of sound-wave propagation above a mixed, striped soft ground that is created by either porous absorbent strips, embedded grooves, or wells with different depths. The accuracy of the model is validated against the boundary element method. It is then used to evaluate the importance of the imaginary part of the admittance of the ground strips on sound attenuation along welled surface. It is shown that the attenuation performance of a surface with multiple impedance discontinuities is high when the imaginary part of the average admittance is large and negative (with an convention), but the magnitudes of the attenuation peaks are also substantially affected by diffraction from the impedance discontinuities.