Helicopter Cabin Noise: Actual vs. Statistical Energy Predictions

Significant strides have occurred in basic understanding and development of analytic modeling techniques through work sponsored by the NASA Langley Research Center. This analytic technique, Statistical Energy Analysis (SEA), and its relationship to prediction of cabin noise, has been presented in the literature and at various workshops (References 1-4). A full scale measurement program performed on the Sikorsky S-76 has provided data for verification of the model. The NASA contract measurement program and the correlation of data and predictions are summarized. SEA predictions are shown to correlate well with full scale data. The material presented represents reasonable verification that the Statistical Energy Analysis method of rotorcraft cabin noise prediction is a feasible and relatively accurate approach, whose output provides not only prediction of velocity or sound pressure levels, but power flow information that reveals the paths taken by the vibratory input energy in the creation of cabin noise. It is now possible to assess the influence structural modifications have on energy flow and the resulting cabin acoustic levels. In addition, damping of structural elements can be evaluated by an efficient and systematic approach.