Please note this is a clear dome only polycarbonate cover for use with the VELUX flat roof kerb. Excellent rain noise reduction All VELUX flat roof windows provide excellent rain noise reduction. The special structure of the dome deflects the noise, while the combination of an exterior dome, double-glazed low-energy pane and insulated kerb reduces noise considerably. Together, they provide protection from rain and hail noise as well as aircraft and traffic noise, and other disturbances.