On the acoustical protection of acoustic balconies

Acoustic balcony is a recent development in Hong Kong for use as a noise screening device on high-rise building façades. It is in principle a balcony equipped with sound absorption materials (NRC 0.7) on its ceiling and side walls, as well as an inclined panel at its parapet. Windows are installed on the space above the parapet to block the direct noise intrusion path from outside to the indoor. In the present study, a full size balcony mockup is adopted in an open-air laboratory and the sound transmission loss of the balcony at different sound source orientations and elevations examined. A long linear loudspeaker array is used to mimic road traffic/ railway noise. The traffic/ railway noise transmission loss increases with source elevation under the effect of the inclined panel. For source elevation not larger than 45 deg, the difference between indoor and outdoor noise levels in the presence of the acoustic balcony with adjusted traffic noise spectrum varies from 10 dBA to 18 dBA while with adjusted railway noise spectrum varies from 11 dBA to 17 dBA.