Abstract: An electromagnetic vibration generator includes a housing, a U-shaped magnet core disposed in the housing and having parallel-extending legs each terminating in a pole face, and an excitation winding inserted on each core leg. The magnet core is encased in cast resin in the housing. The vibration generator further has an armature adapted to be vibrated by an excitation current flowing through the excitation winding. The armature is separated from the pole faces by an air gap. Arrangements are provided for reducing effects of heat expansion of components of the vibration generator on the air gap width.