Sound Field on Balconies
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Environmental noise caused by traffic, industrial and recreational activities is an increasing problem affecting more and more people in their homes, especially in urban areas. Balconies attached to building façades can be found all over the world. In addition to being an open-air area, balconies are often installed so as to decrease the noise reaching the building façade in order to reduce the indoor noise level. As reduction of environmental noise is difficult because it would require attenuation of the sound power level radiated from the sources , the use of balconies can be an efficient way to solve some of the problems caused by noise. The effect of the balconies on the incoming sound levels depend on several factors, such as the geometry of the balcony cavity, the acoustic properties of the materials used in the construction of the balcony, the position of the sound source etc. Will the balcony contribute to a reduction of the sound pressure level or quite the opposite? The scope of this thesis is mainly to investigate the sound field on balconies with different structures. Most of the balconies studied have a closed or partly closed parapet and roof. The aim of this thesis is to find a way to predict the sound field on balconies. The results can be used for further investigations of balconies in order to be able to make better standards for sound field corrections for balconies in the future. Measurements of sound pressure levels excited by a loudspeaker on the ground have been made at six different balconies. The results are analysed and evaluated, and comparisons to the same systems calculated in ODEON has been carried out. Both sound pressure levels in one-third octave bands and A-weighted equivalent sound pressure levels will be investigated. In addition, an analysis of the sound radiation from the sound source has been executed. To get an idea of uncertainties with these kinds of measurements, one of the six balconies examined has been measured three times with a replication of the measurement setup for each test. The results prove that the elevation angle of incident sound plays a significant role on the sound field on balconies. Similar patterns were shown in the frequency range of the sound field on squared balconies with closed parapets. For these balconies the amplification of the sound pressure levels at the façade was largest for measurements where the whole balcony roof was hit by direct waves with at large incident elevation angle. Comparison between measured and simulated sound pressure level values agrees well. The mean and standard deviation of the differences between measured and simulated sound pressure levels in octave bands were 4.03 and 3.64 dB, respectively. For A-weighted equivalent sound pressure levels the mean and standard deviation were 3.08 and 2.75 dB, respectively.