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Helicopter airframe vibration transmission modeling using statistical energy analysis (SEA)

1983; Acoustical Society of America; Volume: 74; Issue: S1 Linguagem: Inglês

10.1121/1.2021101

1520-9024

Charles A. Yoerkie,

Vehicle Noise and Vibration Control

Predicting helicopter cabin noise is a complex issue. It involves sources which are both acoustic/aerodynamic and vibratory in nature as well as a compact, highly interconnected airframe structure. Energy transmits to the cabin via both airframe structureborne and airborne paths. Since a large number of resonant structural and acoustic modes are excited, a statistical approach, which treats the response of the modes collectively in groups, is desirable. The method described for modeling the helicopter airframe and cabin interior is Statistical Energy Analysis (SEA). An SEA model, funded by a NASA Langley Research Center contract, is presented for the Sikorsky S-76 (a4-13 passenger commercial helicopter). This overall source-to-receiver modeling approach allows for evaluation of various noise control measures in the conceptual design stage. Expressions have been developed for SEA parameters and the coupling loss factor has been related to the more familiar vibration transmission coefficient. A full scale measurement program was conducted on the Sikorsky S-76. Data are presented showing the SEA parameters and comparisons with the analytic model. These data include vibration transmission along the beam/panel structure and transmission through intermediate acoustic spaces connected by both resonant and nonresonant conditions. In addition, data are presented concerning the effects of coherent and noncoherent source excitations at distant response points. [Work supported by NASA Langley.]