Sound radiation of parallelly stiffened plates under convected harmonic pressure excitation

The radiation of noise from a parallelly rib-stiffened skin plate of aircraft cabin fuselage in the presence of external mean flow is theoretically investigated. An aero-acoustic-elastic model is developed and used to calculate the radiated sound pressure level (SPL) versus frequency curves with reference to sound radiation of a bare plate immersed in a steady fluid. The flexural and rotational motions of the rib stiffeners are described by applying the Euler-Bernoulli beam theory and torsional wave equation, respectively. Therefore, the coupling forces and moments between the ribs and the face-panel, caused separately by flexural and rotational motion of the ribs, are both taken into account. Given the periodicity of the structure, the Fourier transform technique is employed to solve panel vibration equations and acoustic equations. Systematic parametric investigation demonstrates that the presence of mean flow as well as rib spacings play significant roles in the sound radiation behavior of parallelly rib-stiffened plates. The proposed model provides a convenient and efficient tool for the factual engineering design of this kind of periodic structures with acoustic requirements.