The sound insulation across the plenum window with staggered sound scatter arrays

In this study, experiments and simulations were carried out by a scaled-down model in a semi-anechoic chamber to investigate the acoustic effect of the staggered sound scatter array on the sound insulation of a plenum window. The 1/4 scaled-down plenum window has a gap of 98 mm and the diameter of the sound scatter cylinder is 19 mm. Firstly, the reverberation times of the verified case and reference case were presented to explore the possible effect of the installment of the sound scatter array on the reverberation of the room model. Next, the effect of four sound scatter array arrangements on the sound insulation of the plenum window was analyzed experimentally and numerically. Results show that the installment of the staggered sound scatter array can enhance the sound insulation of the plenum window. Below 600 Hz, enhancement of the staggered sound scatter array on the sound insulation of the plenum window is lower than 2.2 dB. Beyond 600 Hz, the extra transmission loss increases with the frequency and is up to around 6.0 dB. In addition, the trapped mode was observed inside the window cavity and it excited a second higher gap mode which helps improve the sound insulation of the plenum window.