Scale model study on acoustical benefits of plenum window at various azimuthal sound incidences

Noise problem due to traffic roads has become more and more serious in densely populated cities. As the noise level keeps on increasing, opening the windows for natural ventilation has become nearly not possible. A staggered inlet and outlet openings design window, called as plenum window which can provide a good sound insulation as well as allow some natural ventilation passing through window itself was investigated in the present study. The acoustical insertion losses offered by plenum windows under the exposure to traffic noise when windows were not parallel to the line source was investigated using 1:4 scale down model and a 5m long loudspeaker array. The influence of sound incident angles onto plenum windows are found to be significant in protecting traffic noise because of its staggered design. There was about 6dBA to 8dBA variation of insertion loss over the studied angle range. Higher insertion loss obtained when the devices placed nearly normal incidence to the line source.