Air-source heat pumps typically feature an external unit with an axial fan to blow airthrough the heat exchanger. Due to the annoyance (and regulations) ofthe noise emissions of the fan, manufacturers try to achieve as low-noiseconfiguration as possible while keeping the target pressure and volume flow. Thisproject aimed to develop a low-noise fan with reasonable efficiency at a set ofoperating points within structural and geometric constraints.To obtain a low-noise fan design, an automated optimization procedure wasdeveloped. This optimization is multidisciplinary as the merit functionincorporates the effects of aerodynamics (RANS CFD), acoustics (tonal andbroadband models), structure (FEM), and geometric constraints. For theoptimization, an adaptive surrogate-based optimizer was utilized. This type ofoptimizer not only samples the design variable space and creates an initial surrogatemodel based on the evaluated points, but adaptively improves the surrogate whennew evaluations of the merit function are calculated.The automatically created designs were imported into a CAD system and geometricdetails were added with the goal of reducing the noise emissions even further. Thefinal geometries were 3D-printed with selected laser sintering and mounted on amodular test rig developed in the scope of this project.Our project partners at Empa and OST measured the acoustic and aerodynamicperformance of the different designs, respectively. Additionally, similar fans fromdifferent manufacturers were measured as a reference. The comparison betweenour best designs and the reference shows that we could improve the acousticperformance even more while keeping the required volume flow and fan pressure.