Airborne sound insulation - Roofs Where a school is to be located in an area affected by aircraft noise, special measures are necessary and an acoustic consultant should be appointed. Noise intrusion from heavy traffic or aircraft can be reduced by using Hardrock Dual Density Roofing Boards as part of the roof system, creating a quieter ambience within the building.For High performance acoustic specifications, the use of a mass layer may be required. The combination of Hardrock Dual Density and Rockwool Acoustic Membrane results in improved sound insulation levels across the frequency range. Hear the difference in noise levels of airborne sound. we recommend to use speakers to get the best experience