Full scale model investigation on the acoustical protection of a balcony-like façade device (L).
The acoustical insertion losses produced by a balcony-like structure in front of a window are examined experimentally. The results suggest that the balcony ceiling is the most appropriate location for the installation of artificial sound absorption for the purpose of improving the broadband insertion loss, while the side walls are found to be the second best. Results also indicate that the acoustic modes of the balcony opening and the balcony cavity resonance in a direction normal to the window could have a great impact on the one-third octave band insertion losses. The maximum broadband road traffic noise insertion loss achieved is about 7 dB.
NUMERICAL MODELLING OF THE SOUND FIELD NEAR A TALL BUILDING WITH BALCONIES NEAR A ROAD
A two-dimensional, boundary element numerical model is used to study the sound field in the region of balconies in a tall building close to a roadway. The sound pressure level relative to the free field level is calculated within the balconies on the first four floors, and at positions 1 m outside the external facade. The effects of shielding of the source by the balcony wall are found to be largely cancelled by the strong reflected sound from the ceiling and rear wall of the balcony. The insertion loss resulting from eight different applications of an efficient sound absorbing material to the building surfaces is calculated. It is found that treatment of the ceiling or the rear wall of the balcony is the most efficient in terms of noise reduction, producing values of between about 5 and 8 dB for a broad band spectrum characteristic of A-weighted road traffic noise. The maximum effects obtained for a combination of surface treatments is 10 dB. Spectra of the sound pressure level relative to the free field level are compared for a receiver position in one balcony and it is observed that the main effect of an absorbent is to reduce the high frequency resonance peaks.
THE THEORETICAL MODEL TO OPTIMIZE NOISE BARRIER PERFORMANCE AT THE WINDOW OF A HIGH-RISE BUILDING
This paper attempts to design the horizontal noise barrier near the window at the building facades. Previous results have showed that the insertion loss by the barrier declines for the occurrence of reflection. In this paper, some remedial measures have been studied using the theoretical prediction by Macdonald's and the image receiver theory. The theoretical model results were verified by the scale models tests. By designing an absorptive top screen using the theoretical models, an insertion loss of 17 dB at a frequency of 500 Hz, 20 dB, at a frequency of 1000 Hz and 25 dB and at frequency of 2000 Hz could be obtained. Such performances are higher than the previous windows screens and are comparable with tall barriers or partial enclosures on the roadside. This is particularly useful in high-rise buildings when tall barriers cannot be built.