Determining the Acoustic Far Field for Multirotor Aircraft

Keon Wong Hur, Damaris R. Zachos, Kenneth S. Brentner, Eric Greenwood

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Guidelines exist for the far-field acoustic measurement of conventional helicopters on the basis of prior experience. However, it is not clear that this experience can be translated to novel aircraft configurations having multiple rotors operating at different rotation rates. This paper develops a computational approach for predicting the onset of the far field for rotorcraft, which can be used to inform far-field noise measurement procedures for multirotor aircraft. The proposed procedure is applied to several configurations, including a helicopter main rotor, several small multirotor uncrewed aircraft configurations, and a lift+cruise electrical vertical take-off and landing aircraft. The proposed approach is found to be consistent with the conventional wisdom for helicopter rotors. When applied to small multirotor aircraft with varied sizes and numbers of rotors, the far-field distance was found to scale well with vehicle diameter rather than rotor diameter. However, this far-field distance scaling did not hold for the larger multirotor lift+cruise aircraft, due to the significantly different operating conditions of the rotors. The far-field distance for the lift+cruise aircraft was consistent for both hover and level flight conditions. These results suggest that different far-field measurement guidelines may need to be developed for different classes of multirotor aircraft.

Original languageEnglish (US)
Title of host publicationAutonomous VTOL Technical Meeting and Electric VTOL Symposium 2023
PublisherVertical Flight Society
Number of pages18
ISBN (Electronic)9781713887843
StatePublished - 2023
Event2023 Autonomous VTOL Technical Meeting and Electric VTOL Symposium - Mesa, United States
Duration: Jan 24 2023Jan 26 2023

Publication series

NameAutonomous VTOL Technical Meeting and Electric VTOL Symposium 2023


Conference2023 Autonomous VTOL Technical Meeting and Electric VTOL Symposium
Country/TerritoryUnited States

All Science Journal Classification (ASJC) codes

  • Aerospace Engineering

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