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. (C) 1996 Academic Press Limited