A novel periodic mono-material strut with geometrical discontinuity for helicopter cabin noise reduction

Abstract

In order to reduce the structure-borne noise in the helicopter cabin generated by the main gearbox, this paper proposed a novel periodic mono-material strut with geometrical discontinuity. To design the strut under the realistic requirements in helicopter, both the dynamics and statics behaviors of the strut are considered in the theoretical modeling based on the transfer matrix method and the theoretical formulation. On this basis, the mathematical relationships between the design parameters and the design requirements are obtained. The parametric effects are then analyzed to get the coupling relationships of the design requirements, which provide a basis for parameter selection. A sample strut is subsequently designed for a specific helicopter model. Like the periodic strut with multiple materials, the newly periodic strut with mono-material also has good broadband vibration attenuation characteristics in the targeted frequency range from 500 Hz to 2000 Hz. The measured acceleration attenuation can achieve up to 64% and the attenuations in some frequencies can exceed 40 dB, verifying the feasibility and effectiveness of the strut in attenuating the vibration transmitted from the gearbox to the fuselage.