Measurements on the Aerodynamic Noise Generated from a Tiltrotor

틸트로터에서 발생하는 공력소음의 측정에 관한 연구

In this paper the aeroacoustic characteristics of a tilt-rotor system is measured by using a sealed model tilt-rotor. With a microphone array system and the do-dopplerization algorithm, the location and the characteristics of rotor noise are successfully measured. The most of high frequency noise (4kHz) is found to be located at rotor blade tips, but the low frequency tonal noise is dominant on the middle of the rotor blades. The measured tonal noise characteristics are compared to the results of theoretical calculation. At 0.5m distance from the rotor plane, measured and calculated data are relatively well matched regardless of rotating speed and collective pitch angie for the azimuthal angles between $0^{\circ}\;and\;60^{\circ}$. However, the data on the azimuthal angles between $70^{\circ}\;and\;90^{\circ}$ are not quite comparable. In addition, the compared data for far-field case (1.5m) are quite different. This is probably due to the unsteady effect which if not included in the theoretical calculation.