A semi-analytical model for the prediction of the broadband noise due to the interaction between turbulent rotor wakesandarotorincontra-rotatingopenrotorsispresented.Theunsteadyloadingoftherearrotorismodeledusing classicalisolated flat-platetheory.Striptheoryisusedtotreatthespanwisevariationsofaerodynamicquantitiesand blade geometry. The turbulent wake is assumed to be homogeneous and isotropic turbulence that is modulated by a train of wake profiles. The model is presented in detail and insight into its modal behavior is provided. A parameter study is conducted to investigate the effects of blade number, rotor–rotor gap and rotor speeds on broadband noise emissions due to rotor–wake/rotor interaction in contra-rotating open rotors. Scaling laws for sound power levels have been established analytically and show good agreement with the results of the parameter study. Nomenclature a = empirical wake parameter Bi = blade number of theith rotor bW = half-wake width, m Cd = drag coefficient of front airfoils c0 = speed of sound, m:s � 1 ci = blade chord, m cl