Frequency-domain tonal noise prediction models provide a rapid means of assessing rotational noise, which is particularly useful during the early stages of rotorcraft and propeller design and optimization. This paper presents a comprehensive review of the most widely used frequency-domain models, including four steady loading noise models, three unsteady loading noise models, and three thickness noise models. Unified and consistent formulations are provided for all models, and the contributions of individual terms are grouped and analyzed. The models are then compared under various operating conditions, including steady hover, unsteady hover, axial forward flight, and edgewise forward flight. Overall, the models show good agreement with measurement data, although certain deficiencies have also been identified. Finally, recommendations for model usage under different flight conditions are provided.
Gill et al. (Mon,) studied this question.