# A Psychoacoustic Investigation on the Effect of External Shading Devices on Building Facades
## 4 Summary and Conclusions  
This work represents a first approach to the evaluation of the variability of some psychoacoustic parameters over a building facade, due to the presence of a shading device, both with traditional and sound absorbing louvres. The experimental data were obtained during a measurements campaign conducted on a 1:1 scale model of a portion of a shading device to be installed over a building facade in a semi-anechoic chamber. The acoustic insertion loss given by the shading device model has been discussed in greater detail in [23]. The large amount of impulse response measurements were convolved with two different noise signals in order to calculate loudness, roughness and sharpness, which were evaluated with mutual comparison between the situation with the shading device, in its various configurations, and the blank facade (the floor of the laboratory). The results of the measurements and post-processing procedures generated a large amount of data, which were investigated with an analysis of variance to evaluate the statistical significance of the variations of the sound pressure levels and of the chosen psychoacoustic parameters. The ANOVA tests carried out on the different data-sets highlight that in general the measured differences are statistically significant, with respect to the variations of the sound source position and the louvres' tilt angles. The combination of the two factors is in general not statistically significant. There is a significant difference in the behaviour of the \(\eta_{\mathrm{p}}\)\({}^{2}\) in the separate analysis of the psychoacoustic parameters deriving from the presence of the traditional or the sound absorbing shading system. The effects of the louvres' tilt angle seem to be more relevant with respect to the sound source positions in the data set related to the standard louvres, while the tendency is reverse when the sound absorbing louvres are observed. It is possible to ascribe this fact to the poor sound absorption properties of the standard louvres made of simple plywood: for this reason they play an important role as a barrier when they are un-tilted and they can intercept the acoustic field that comes from below. The opposite tendency is observed for the sound absorbing shading system: this can be attributed to the fact that the expanded melamine used in the experiment modifies the content in frequencies of the sound pressure field arriving on the facade and the louvres' tilt angles are less relevant, in view of the quantity of sound absorbing material. The generated sound field is intercepted by the same amount of material with a small consideration of the louvres' tilt angle, while varying the sound source position. In conclusion, it is possible to affirm that the shading device plays an important role in the variations of sound pressure level and loudness, has quite a good effect on roughness, while it has practically no effect on sharpness. It is possible to say that the traditional shading system has a negative effect as it increases both the sound pressure levels and the loudness over the studied facade portion. The sound absorbing shading device, on the contrary, can reduce both the loudness and the sound pressure level, respectively, by up to 14 phons and 8 dB. The loudness reduction given by the sound absorbing louvres represents an important result, since loudness is a subjective acoustic parameter, more related to human noise perception, if compared with the sound pressure level in dB, or in dB(A). The external shading devices have an important role both in controlling the internal comfort of the building for its users and in reducing the cooling energy consumption. This research highlights that an acoustic optimisation of the louvres can additionally play an important role in reducing not only the sound pressure levels over the building facade, but in particular the magnitude perception of the noise. An accurate research activity is needed in order to study in greater detail the psychoacoustic analysis of the shading devices.