Vibration damper machines; machines for reducing vibration in buildings; active mass dampers for reducing vibration in buildings and other structures; active mass dampers for reducing vibration in the floors of buildings; vibration damper machines for reducing vibration in buildings and other structures; machines for reducing vibration in buildings and other structures; machines for reducing vibration in the floors of buildings; machines for active vibration control; machines for active vibration control of floors of buildings; parts and fitting for the aforesaid goods.