The aeroacoustic characteristics of tilt rotor in hover were investigated based on acoustic test and numerical computation. The test was conducted with isolate model tilt rotor

and the acoustic data of different collective pitch angles and blade tip Mach number were measured. The numerical computation was made based on CFD (computational fluid dynamic) and FW-H(Ffowcs Williams-Hawkings) equation

and the calculation accuracy was validated by test data. The acoustic results of different observation positions were compared

the effects of thrust coefficients and blade tip Mach number on tilt rotor noise were analyzed

and the acoustic characteristics of isolate rotor and dual rotors were calculated. Results showed that

the overall sound pressure level of tilt rotor increased with thrust coefficients and blade tip Mach number

the decrease of tilt rotor blade tip Mach number can reduce overall sound pressure level although the thrust coefficient was increased to maintain rotor lift; the acoustic directivity of dual tilt rotors was longitudinally symmetrical

the local maximum overall sound pressure level occurred at several azimuths

due to the superposition in noise radiation and aerodynamic interaction of the two rotors.