Freeway noise and high-rise balconies

The sound levels on balconies above the 8th floor of high-rise buildings situated 200 ft or so from freeway edge-of-pavements were found to be about 10 dB higher than those occurring on the ground floor. Equivalent sound levels on these balconies during the day were in the range 70–80 dBA depending on the size of the freeway; these sound levels are as high as those at ground level 50 ft from the edge-of-pavements of the freeways concerned. However, the use of sound absorptive material on a normal front-walled balcony was shown to produce substantial noise reductions: treatment of the ceiling alone resulted in a 4–5 dB reduction, while a 7–8 dB reduction occurred with the addition of absorption equal, in Sabins, to a little over one-third the area of the balcony surfaces.