External mean flow influence on noise transmission through double-leaf aeroelastic plates

The transmission of external jet noise through the double-leaf skin plate of an aircraft cabin fuselage in the presence of external mean flow is analytically studied. An aeroacoustic-elastic theoretical model is developed and applied to calculate the sound transmission loss versus frequency curves. Four different types of acoustic phenomenon (i.e., the mass-air-mass resonance, the standing-wave attenuation, the standing-wave resonance, and the coincidence resonance) for a flat double-leaf plate as well as the ring frequency resonance for a curved double-leaf plate are identified. Independently of the proposed theoretical model, simple closed-form formulas for the natural frequencies associated with the preceding acoustic phenomena are derived using physical principles. Excellent agreement between the model predictions and the closed-form formulas is achieved. Systematical parametric investigation with the model demonstrate that the presence of the mean flow as well as the sound incidence angles substantially affect the sound transmission behavior of the double-leaf structure. The influences of the panel curvature together with cabin internal pressure on jet noise transmission are also significant and should be taken into account when designing aircraft cabin fuselages.