Efimtsov B., Lazarev L.

The acoustic field in a closed cylindrical shell of finite length with a regular orthogonal system stiffeners (stringers and frames) which models the propeller aircraft fuselage section is investigated. An analytical model accounting for frame discreteness and for their elasto-inertial properties is examined. The stringers in this case are “smeared”. The eigen-frequency density corresponding to this analytical model has maxima not only in the vicinity of the ring frequency but also in the vicinity of the frequencies characteristic of regular structures. Shell excitation by the aero-acoustic field of propeller and a formation of the sound field in the shell are described with account for the effects of a strong elasto-acoustic interaction between its oscillations and the sound-transmitting layers, the ambience and the medium in the limited volume. The analysis, of the acoustic field inside aircraft within the limits of this analytical model permitted determining the conditions at which the framed shell of the fuselage can be treated as orthotropic one and the conditions at which the frame discreteness and their elasto-inertial properties, are to be taken into account.