An Investigation of Impulsive Rotor Noise Using a Model Rotor

The investigation of gust induced impulsive rotor noise was made using a 3 bladed 9ft. diameter model rotor. The gust was produced by a series of air-jets placed under the rotor disc and the noise characteristics were determined for a range of gust lengths and amplitudes. The main emphasis was placed on experimental measurements and. theoretical prediction of discrete noise. The theoretical estimation of discrete noise was made using a simple point dipole theory and a more complex rotational noise theory. The theoretical results have been compared with measurements and show good agreement both in amplitude and characteristics over the full range of gust profiles used in the experimental programme. Broadband noise characteristics have also been reviewed in relation to possible blade stall.