A stator or rotor of an electric motor or generator comprises a core formed of ferromagnetic material having a plurality of teeth arranged circumferentially about an axis. In one aspect of the invention, at least one retaining member connects the end portions of at least two of the teeth to each other in a manner inhibiting relative movement between said tooth end portions. By inhibiting relative movement between said tooth end portions, vibration is reduced. Vibration can also be reduced by welding interior surfaces of a core to each other. Reducing the vibration reduces the noise emissions of the rotor or stator during operation.