TREATED CABIN ACOUSTIC PREDICTION USING STATISTICAL ENERGY ANALYSIS

The purpose of this paper is to demonstrate the application of statistical energy analysis (SEA) to the modeling and design of helicopter cabin interior noise control treatment. The information presented is derived from work sponsored by the NASA Langley Research Center for the development of analytic modeling techniques and basic understanding of the complex nature of cabin noise. Previously reported efforts focused on SEA modeling of the untreated aircraft configuration. The interior treatment configurations modeled in the present paper are a Utility and an Executive. The Utility and Executive interior models are developed directly from existing S-76 aircraft designs. The Utility interior design priority is light weight with reasonable acoustic benefits; while in the Executive interior, emphasis is primarily on improving the acoustic environment while allowing for increased interior weight. The relative importance of panel transmission loss (TL), acoustic leakage, and absorption to the control of cabin noise is demonstrated using the SEA modeling parameters. It is shown that the major cabin noise improvement below 1000 Hz comes from increased panel TL, while above 1000 Hz it comes from reduced acoustic leakage and increased absorption in the cabin and overhead cavities. Laboratory measurements of typical Utility and Executive interior panels are shown to compare well with SEA predictions. Additionally, a very good correlation exists between SEA model predictions and their corresponding aircraft flight noise levels. Thus a viable technique for aircraft noise control design is established from which new concepts can be evaluated with relative ease.