International audience ; Lightweight buildings are increasingly popular in Europe due to their lower carbon footprint, speed of construction and flexibility in the design of spaces. However, the inherent lightness of its structure affects sound and vibration insulation properties, especially at low frequencies. Washing machines represent a difficult equipment to insulate, due to their complex dynamic behaviours and the variety of phases during their working cycle. A unique solution is not yet available to tackle the washing machine noise problem in which the elements to account are multiples: machinery (source), structure (receiver), coupling condition (connection) and annoyance perceived by users. In this case study, part of the ITN project ?Acoutect?, the behaviour of a washing machine situated over a real lightweight wooden joists floor has been analysed. Measurements with accelerometers and binaural recordings have been performed in a two-storey masonry house in the Netherlands, in which the first floor (source room) is used as laundry while the room underneath (receiving room) is used as bedroom. The core idea of the approach is to split the characterisation of the problem in two binaries, merging technical solution and user perception. The results from a subjective evaluation serve as basis for the design of the optimal solution, targeting the specific frequency range of the different washing cycles causing major disturbance on the users.