Point source radiation through a composite medium

The paper considers the acoustic radiation due to a point source in the close vicinity of a composite medium consisting of different fluid strata in motion. The results are derived in general and agree with those obtained in special cases. The most interesting result of the analysis is the prediction of the existence of an “aerodynamic zone of silence” along the vortex discontinuities of the composite medium. Apart from producing the usual reflexion coefficient valid at an interface separating a fluid at rest from a fluid in motion (which is in agreement with the one obtained by Miles [1] and Ffowcs Williams [2]), the analysis also provides a general expression for the reflexion coefficient.