Low speed axial fans are widely used in industrial application, such as in HVAC and cooling systems, but their acoustic signature can significantly impact comfort and noise regulation compliance. Fan noise generally consists of broadband and tonal components. Tonal noise is often perceived as more annoying due to its distinct, periodic character, making it a critical target for mitigation strategies. Traditional noise reduction strategies often involve complex modifications to blade design or active control techniques, which can be costly or impractical. This thesis investigates an alternative numerical approach for reducing tonal noise at the Blade Passing Frequency via a flow obstruction placed upstream of the fan.