An analysis is made of sound generation by aerodynamic sources near an acoustically compact body (or compact surface feature on a large boundary) that can deform in an arbitrary manner. It is shown how such problems can be investigated by simple extension of the compact Green's function used in the treatment of compact rigid bodies. It is known that this method can furnish rapid and accurate predictions of sound generated by flows with extensive, non-compact distributions of sources in cases where a numerical treatment requires at best tens or hundreds of hours of CPU time. Illustrative applications are made to study (i) the sound generated by a nominally rigid circular lamina of time-dependent radius held in an irrotational mean stream, and (ii) the production of voiced speech by vorticity interacting with a simple model of the vocal folds. In case (ii), it appears that predictions are represented well by a quasi-static approximation that permits the particular results of this paper and previous investigations to be generalized to arbitrarily configured folds.
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Howe et al. (2007) studied this question.