Methodologies for helicopter noise footprint prediction in maneuvering flights

This paper investigates different techniques for the evaluation of the acoustic disturbance emitted by helicopters in unsteady maneuvers. Nowadays, the simulation of noise emitted by helicopters is of great interest to designers, both for assessing the acoustic impact of helicopter flight on communities and for identifying optimal-noise trajectories. Typically, these simulations consists in the atmospheric propagation of a near-field noise model, extracted from an appropriate database determined through steady-state flight simulations/measurements. In this work, two steady-flight/unsteady-flight noise equivalence criteria are examined, in order to assess their suitability by comparison with noise predictions directly evaluated through a fully-unsteady aeroacoustic solver. They differ in the flight parameters used to select the near-field noise model within the database to be associated to a given unsteady-flight condition.