The sound reduction of open windows is limited and therefore noise break-in can be a real issue, restricting the opportunity for simple natural ventilation opportunities on projects with higher noise levels. MACH has therefore taken the next step in enhancing the acoustic performance of open windows, allowing natural ventilation to be utilised on more acoustically challenging sites. This case study therefore provides details of in house FDTD modelling and acoustic testing window Baffles options specifically designed to maximise natural ventilation options.