Velocity dependent comparison of tonal propeller noise prediction methods against flyover measurements of small propeller aircraft

Abstract

This study presents and applies a noise prediction toolchain for propeller aircraft, specifically designed for the preliminary design environment. The work compares two aerodynamic modeling approaches for propeller load prediction: a simple BEMT method and a full 3D aerodynamic model. Additionally, it evaluates tonal noise predictions from Hanson’s and Farassat’s models against flyover noise measurements of a Do 228 aircraft under various operating conditions. The comprehensive analysis assesses model performance across different velocity regimes to refine PANAM’s capabilities for accurately predicting propeller noise characteristics of small aircraft, thereby advancing acoustic assessment methodologies in preliminary aircraft design. Key findings reveal that maximum sound pressure levels increase with both airspeed and rotational speed. Flight speed significantly influences the radial position of the thrust peak, shifting it outward from approximately 65 % to 85 % of the blade radius as speed increases. However, this outward shift does not significantly affect tonal noise emission. While both noise models successfully predict the velocity trend, simulations consistently underpredict noise levels by 3 dB to 5 dB compared to experimental data.