A simplified model to evaluate noise reduction interventions in the urban environment

Traffic noise is a major problem in all large cities. The surface acoustical characteristics (e.g. referred to
roads, pedestrian traffic areas, building façades, building surfaces, in general) affect the noise propagation
in the urban environment. Through a better outdoor design and management (e.g. by means of green
areas, porous asphalt, speed control), or building refurbishment actions (acoustic plaster, absorbing
shading devices), the increasing of surface absorption could be useful to mitigate noise environmental
pollution, and therefore to reduce the sound levels in the proximity of the building façades for their
entire height. The reduction of the noise levels outside the buildings would determine lower indoor noise
levels, and therefore a better situation, without direct actions on the building walls. Through a series
of noise propagation calculations in urban environments, by means of a three-dimensional simulation
model, the influence of some configurations and the potential impact of some intervention solutions are
quantified. In the first stage of the research, the analysis of a simplified model is conducted, to evaluate
the influence of noise on the building façades, based on a simplified geometry of the urban environment
and of the surface acoustic features. The same analysis is validated by means of a more detailed model,
corresponding to the configuration of an existing built area, to verify if the analyses performed by
means of the simplified model can be extended to more complex layouts. Successively, calculations are
developed to quantify the noise levels that occur with different acoustic (absorption of façades, soil,
asphalt, or green elements) and geometric (road width, buildings height, presence of balconies, etc.)
characteristics to show the potential reduction given by some interventions. Solutions that can lead to
a more significant reduction of the noise in correspondence of the façades are then summarized. The
simplified geometrical model appears to be suitable for preliminary investigations as the maximum error
found for narrower roads is equal to 17%.