The objective of the work described in this paper is to set up and validate an adjoint based method for blade shape optimisation aiming at propeller noise reduction. As a first step toward a comprehensive propeller noise optimisation, the present study focuses on the loading noise of a single propeller isolated and without incidence. In this respect, an acoustic objective function is derived, based on the Hanson-Léwy steady loading noise formulation. After defining this function, the first step is to derive its sensitivities to mesh and aerodynamic field parameters. Once implemented in the ONERA adjoint based optimisation procedure, the acoustic function predictions are compared to a classical Ffowcs Williams and Hawkings approach, and the sensitivities are validated by comparison with the finite differences method.