The effect of a frame around glass fixed windows on outdoor-indoor transmission class (OITC) was studied here. Three frame materials were selected, i.e., timber, Aluminum and unplasticized Poly Vinyl Chloride (uPVC). The use of real open window (to differentiate it from partially open double layered window) for natural ventilation was also studied. The top hung style was selected due to common usage and the possibility of noise blockage by the shutter. Laboratory test complies with ASTM E-90 was employed. The study showed that weight and density, which play significant roles in sound insulation quality of a material was not borne out for the window frame. Here, timber as the heaviest material gave lowest OITC and transmission loss (TL) contour. This was due to the absence of sealant and rubber strips which are unusual for timber caused by large thermal expansion coefficient. Top hung openings of 5° and 10° showed similar transmission loss contours, but the OITC of the 5° open window was slightly higher than the 10°.
