Graphical Abstract Figure
Modal contributions to the narrowband (6.1 Hz binwidth) SPL at the 120 deg farfield microphone (FF019) at 60% speed settingtotal noise signature, m = 0, ±1, ±2, color coded as in legend, dash-dotted magenta line: cumulative contribution from m = 0, ±1; standard-array orientation.
Graphical Abstract Figure
Modal contributions to the narrowband (6.1 Hz binwidth) SPL at the 120 deg farfield microphone (FF019) at 60% speed settingtotal noise signature, m = 0, ±1, ±2, color coded as in legend, dash-dotted magenta line: cumulative contribution from m = 0, ±1; standard-array orientation.
Abstract
Acoustic data obtained using a small turbofan engine are further analyzed to improve the understanding of core/combustor noise. The relative impact of this propulsion-noise source for civilian-transport aircraft on airport community noise is expected to significantly increase in the future. Simultaneous high-data-rate acoustic measurements acquired using a circumferential infinite-tube-probe array at the core-nozzle exit in conjunction with a farfield microphone array are processed. The test matrix contains engine operational points from idle to the engine-maximum setting, with measurements repeated for different circumferential array configurations, as well as for redundancy. The combustor-noise contribution to the farfield noise signature is obtained using an advanced source-separation method that correlates the farfield microphone measurements with a modal decomposition of the unsteady pressure field at the core-nozzle exit. The advantages of the present approach compared to the classical two-signal source-separation method are discussed.
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