Improving the noise reduction by green roofs due to solar panels and substrate shaping

The urban fabric largely consists of acoustically rigid materials. This not only affects sound pressure levels in streets, but also how sound propagates towards the back side of a building or to connected urban canyons. A green roof is a practical solution to have roof absorption, mitigating diffracting sound waves. Flat green roofs were shown to provide roughly 3？dBA urban road traffic noise reduction relative to a common flat rigid roof. Although already relevant, it has been numerically studied in this work how the green roof insertion loss of flat roofs can be further increased. Solar panels on green roofs were found to significantly decrease sound pressure levels at the shielded building facade, up to 5？dBA on top of the insertion loss of granular substrates. Polyurethane foam slabs as green roof substrates provide relevant shielding when placed on a series of hollow trapezium-like cores of sufficient height