The purpose of this paper is to demonstrate that at small values of the Mach number a harmonically rich radiated field will result from the simple harmonic (sinusoidal) motion of an oscillating body when the amplitude of oscillation is large. An asymptotic solution of the equations of inviscid compressible flow is obtained which is valid in the small Mach number limit. To a given order of approximation, the effects of fluid nonlinearity (nonlinearity in the equations of motion and the equation of state) do not enter, and the harmonic distortion is due entirely to large-amplitude boundary motion. In higher approximations, where both the effects of boundary motion and fluid nonlinearity enter, the former effect can still control the amplitude of certain harmonics of the radiated acoustic field. The results are obtained by the method of matched asymptotic expansions, which is ideally suited for the purpose of distinguishing the harmonic distortion due to large displacements from that due to fluid nonlinearity. The method is used to make the connection between the field far from the source, and the nonpropagating hydrodynamic flow field near the oscillating body. Subject Classification: 25.55; 20.15, 20.60.
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Frost et al. (1975) studied this question.