Open windows with better sound insulation

Nearly 1/3 of the Danish homes are estimated to be exposed to a road noise level greater than the limit threshold of 58 dB Lden. The Danish Environmental Protection Agency's guideline from 2007 "Noise from roads" introduces noise limits with open windows (opening area of 0.35 m2) for certain situations. With a moderate/high outdoor noise level from traffic, railway or industry these noise limits cannot be complied with for traditional windows, but requires windows with better sound insulation in open position. For this project three overall window types has been investigated; 1: Further improving the Supply Air Window with special attention to low frequencies, e.g. different types, placement and dimensions of absorbers and resonators have been verified. 2: Double window with focus on the inner cavity between the windows, where different kinds and length of sound barriers have been explored. 3: Single window with different types and placement of (outer) attachments, in the form of sound traps.The project has been initiated by a literature study followed by several laboratory measurement series. Compared to a single window opened 0.35 m2 the sound reduction improvements depending on window type (for Rw +Ctr) are in the magnitude of 18/7/10 dB.