Quick-Step Quiet-Step is the most superior underlay on the market. The underlay provides a 30% reduction in reflected foot noise, which is most suitable in multi storey commercial buildings or residential buildings that require sound insulation. The Quiet-Step Combi-Lay is the first floating floor underlay in Australia to take reflected foot noise under serious consideration. The underlay has achieved an excellent L’nw + C1 = 47 rating in multi-storey applications. The Quiet-Step Combi-Lay also comes in a 4 mm thickness.