We study the motion and sound of a thin elastic plate actuated at its leading edge by small-amplitude periodic pitchingand heaving, and subject to uniform low-Mach flow. When the frequency of actuation coincides with an eigenfrequencyΩ_(res) of the unforced plate, a resonance motion is excited and the plate oscillates at the corresponding eigenmode. Thedynamical description is used to formulate the acoustic problem, where the sources of sound include the plate velocity andfluid vorticity. Acoustic radiation of a dipole type is calculated and discussed in the limit where the plate is acousticallycompact. It is found that plate elasticity has opposite effects on sound radiation, depending on the forcing frequency: atfrequencies close to Ω_(res), the near-resonancemotion results in the generation of high sound levels; however, at frequenciesfar from res, plate elasticity reduces the amplitude of plate deflection (compared to that of a rigid plate), leading to noisereduction. The results identify the trailing edge noise as the main source of sound, dominating the sound generated bydirect plate motion. The analysis is suggested as a preliminary tool for examining the acoustic signature of flapping flight,common in insects and flapping micro-air-vehicles.
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