ASSESSMENT OF NOISE-CONTROL MEASURES FOR A MODEL ADVANCED DUCTED PROPULSOR

This article presents a study of estimated full scale noise levels bas ed on measured Levels from the advanced ducted propulsor subscale mode l. Testing of this model was performed in the NASA Lewis Low Speed Ane choic Wind Tunnel at a simulated takeoff condition of Mach 0.2, Potent ial benefits of two noise control approaches were evaluated. The effec t of active noise control (ANC) on the effective perceived noise level (EPNL) was evaluated by artificially removing various rotor/stator in teraction tones. The effect of a passive exhaust duct liner on the fan EPNL was modeled by applying a predicted noise attenuation spectrum t o the measured data. The effect of hybrid active-passive control (whic h implements both the ANC and passive exhaust duct liner), was also ev aluated. EPNL values are approximate because the original source data were limited in bandwidth and in sideline angular coverage. The main e mphasis is on comparisons between the baseline and configurations with simulated noise control measures.