A single skin construction, has relatively low mass and the internal surface is effectively directly coupled with the external surface.
For airborne noise there will be very little energy absorption and the majority of sound reduction will be due to internal reflection. Increasing the gauge of the cladding, the profile or the purlin spacing will slightly alter the stiffness and the resonant frequency of the panel, which will change the position of the coincident dip.
Rain impact noise will also be directly transmitted through the single skin and internal rain noise levels will be high.
The use of the Coverworld ‘Non-Drip’ backing would give a further sound reduction of 2dB as it provides an additional layer and due to its composition it helps to absorb more sound.