Turbulent boundary layer trailing edge noise is becoming an increasingly important problem in wind turbine applications. The wind turbine rotor diameter is expected to keep growing bigger in the future and trailing edge noise is known to scale with the relative rotor tip velocity to the power 5-6. One effective and yet relatively novel method to reduce this type of noise is the addition of perforated add-on devices to the rear end of the rotor blades. The perforated add-ons have been extensively tested experimentally in recent years. The experimental studies have been instrumental in developing design rules but currently, the precise mechanisms behind this noise reduction are not yet fully understood. The project objective is to obtain insights into the aero-acoustic flow physics responsible for the far-field noise reduction for perforated add-on trailing edge noise problems. To accomplish this, the first high-fidelity numerical LBM study in which the geometry of the per- forations is fully resolved is performed. The simulation is performed with the commercial Lattice Boltzmann method-based solver, PowerFLOW. A scaled 2.5D airfoil simulation is performed with an inflow of 20 [m/s] in lifting conditions. Three different airfoil add-on configurations are simulated. One baseline, one with a homogenous perforation spacing, and one geometry where this spacing is decreasing in the downstream direction. The simulation results are validated against experiments and a noise reduction of about 3 − 4 [dB] is found for in the lower frequency range Stc < 10. A distribution of sound sources was found over the add-on for all frequencies. The frequencies up to Stc = 10 show signs of destructive acoustic interference contributing to the observed noise reduction. Besides this phenomenon, two additional mechanisms were identified as contributing to the observed noise reduction. The second is the milder ∆p jump at the trailing edge caused by communicating boundary layers on both sides of the add-on. A good indication of this milder pressure jump is the correlation coefficient Rpp between two points on opposite sides of the add-on close to the edge. No development or growth of the zone of the correlation coefficient was found over the add-on except for the vicinity close to the trailing edge. A mean vertical upward flow is observed, flowing out of and extending above the perforations. This is believed to be relevant for the achieved noise reduction. The effect possibly has simultaneous positive and negative conflicting contributions to noise reduction. Lastly, it was concluded that the spectra of the homogeneous and linear perforated geometries showed too much similarity, therefore it was difficult to couple discrepancies in the near-field between the two cases to observations of the far-field spectra.