Noise reduction of enhanced acoustic balconies on a high-rise building block

Abstract

A new device called 'enhanced acoustic balcony' is installed in a new housing estate in Hong Kong. It is intended to help reduce the impact of traffic noise on the residents. This balcony is basically an enlarged form of a plenum window and with three openings. Apart from the outdoor air inlet, there is the balcony door and a side-hung window on the interior balcony wall for natural ventilation of the indoor space. Sound absorption of NRC 0.7 is installed on the balcony ceiling and its sidewall facing the incoming traffic noise and an inclined panel is installed outside the balcony to provide noise screening. A site measurement of its noise reduction is carried out in the present study in a newly completed housing block. A 28 m long loudspeaker array is used as the sound source. The indoor noise levels are measured according to ISO standard. The results show that the difference between indoor and outdoor noise levels in the presence of this balcony form varies over a relatively narrow range between 10 to 13 dBA for an elevation angle from 25 to 60 deg. There is a weak increase of the noise level difference with elevation angle.