Propellers usually operate in non-uniform flows, which is expected to modify the behaviour of the emitted noise field. In this framework, an experimental campaign with far-field noise measurements of a two-blade propeller, immersed in a non-uniform flow, has been performed in the anechoic facility at the University of Southampton. A parametric analysis of the effects of different flow non-uniformities, generated by different masks positioned at the nozzle exhaust, was performed at constant thrust. Results show that non-uniformities in the incoming flow exalt the interaction tones. Tonal peaks, starting from the third blade passage frequency harmonic, register variations in the order of tens of decibels, up to a maximum of 12dB. Experimental outcomes are compared with tonal noise predictions obtained by using a frequency domain formulation, based on integrating the aerodynamic sources on the proper surface of the blade. The model captures the main features of the interaction tones and a good agreement is reached between measured and predicted values in both sound pressure levels and directivity.