Study of vertical noise profile through Helium filled-balloon measurements in the city of Milan

Considering the actual “vertical” housing development in the last few decades, the number of people living in high-rise building is continuously increasing. At present in the city of Milanmore than 500 (0.4% of total) buildings exceed the height of 50 m, with a number of residents of about 14000 (1% of total). For this reason, we planned an experimental campaign to study the vertical noise profile through air-balloon measurements in the city of Milan. Results show that the noise levels increase with the height with respect to ground-reference measurements, as a result of the contribution from an extended area. The highest levels are reached at about 90 m. Critical issues regarding this measurement technique are also outlined.