Perceptually validated auralization of brushless direct current motor-propeller noise via torque ripple-induced rotational speed fluctuation modeling

Psychoacoustic assessment of aircraft under development is hindered by the difficulty of obtaining comprehensive noise data before physical prototypes are available. For the brushless direct current motor-propeller systems that are primary noise sources on these aircraft, this study develops and validates a physics-based auralization framework that models rotational speed fluctuations induced by electromagnetic torque ripple. The model incorporates both stochastic (rotational speed fluctuation strength) and deterministic periodic [iterative polynomial function (IPF)] components. A key feature is that the IPF is mathematically derived from motor pole pairs (Nf=k·Np), linking electromagnetic physics directly to acoustic modulation. Physical validation confirmed the model's improved accuracy in predicting high-frequency tonal components compared to conventional constant-speed approaches. Perceptual validation with 61 participants was conducted through two psychoacoustic experiments. The subjective response test provided statistical evidence that listeners did not reliably distinguish between the measured sounds and the auralized sounds incorporating the ripple model. Annoyance tests confirmed loudness-dominated responses with strong psychoacoustic model correlations. These findings establish that the validated framework can effectively substitute for physical measurements in psychoacoustic assessments. This enables perception-informed design of acoustically acceptable electric vertical takeoff and landing vehicles before physical prototypes are available.