Abstract: A vibration assembly comprising a housing (12) having a central cavity (20) and a pair of side cavities (22, 24) of radially smaller dimension than that of the central cavity, all of which extends axially about an axis (26) from opposed ends of the central cavity. A piston (50) is housed within the cavities (20, 22, 24) and includes a mass (52) disposed within the central cavity (20) and a pair of supports (54, 56) which are disposed within respective ones of the cavity pair (24, 22) and which extend axially from the mass. The supports (54, 56) have radial dimensions which are substantially the same as those of the pair of cavities (22, 24). The mass (52) and the supports have axial dimensions which are substantially less than those respectively of the central cavity means and of the pair of cavities (20, 22, 24) for enabling the piston (50) to move axially within the cavities.