Recent advances in aircraft source noise synthesis

For several decades, research and development has been conducted at the NASA Langley Research Center directed at understanding human response to aircraft flyover noise. More recently, a technology development effort has focused on the simulation of aircraft flyover noise associated with future, large commercial transports. Because recordings of future aircraft are not available, the approach taken utilizes source noise predictions of engine and airframe components which serve as a basis for source noise syntheses. Human subject response studies have been conducted aimed at determining the fidelity of synthesized source noise, and the annoyance and detectability once the noise is propagated (via simulation) to the ground. Driven by various factors, human response to less common noise sources are gaining interest. Some have been around for a long time (rotorcraft), some have come and gone, and are back again (open rotors), and some are entirely new (distributed electric driven propeller systems). Each has unique challenges associated with source noise synthesis. Discussed in this work are some of those challenges including source noise characterization from wind tunnel data, flight data, or prediction; factors affecting perceptual fidelity including tonal/broadband separation, and amplitude and frequency modulation; and a potentially expansive range of operating conditions.