Ubbink 125mm Sound Attenuator This sound attenuator from Ubbink has been designed to help to minimise the sounds that are produced by fans and other machinery used in heating, cooling and air conditioning systems. The sound attenuator is flexible to allow easy installation and movement in and around complex structures. The Ubbink 125mm sound attenuator consists of 3 layers: a non-woven cloth inner layer, a 25mm glass wool insulation layer, and an aluminium laminate outer layer.