Gilles A. Daigle
Inst. for Microstruct. Sci., Natl. Res. Council, Ottawa, ON K1A 0R6, Canada
Henry E. Bass
Univ. of Mississippi, University, MS 38677
Propagation of sound in the atmosphere is governed by a number of interacting physical mechanisms including geometrical spreading, molecular absorption, reflection from a complex impedance boundary, refraction, diffraction, and scattering. Accurate predictions of sound transmission loss from a source to a receiver must somehow account for all of these phenomena simultaneously. Although this goal is beyond current capabilities, the application of numerical techniques to solve the full wave equation has led to significant advances. Current implementations agree well with experiments for low turbulence and flat ground. At moderate ranges, even the effects of turbulence can be accounted for. Members of NATO Panel 3 Research Study Group 11 began an effort in 1990 to compare predictions of the various models and different implementations of the same model with the goal of identifying any differences and sources of those differences and to provide benchmark cases which future researchers can use to check new models. Further, the amount of well-documented experimental data to which the numerical solutions can be compared is very limited. During the summer of 1991, a Joint Acoustic Propagation Experiment (JAPE) was organized in order to extend the database. This paper will summarize the benchmark effort, review the available experimental data and comparison to theory prior to the JAPE, and finally, summarize the JAPE.