Rudder quiet during cruise in calm air
Rudder position during cruise in calm air is steady (centered at zero except when rudder trim is inserted to balance a directional asymmetry such as an engine out). The rudder will only move in response to disturbance inputs or in conjunction with pilot or autopilot commands to maneuver laterally. In addition to Dutch Roll damping at approximately 0.25Hz, some modern commercial transports include rudder control to damp structural modes with frequencies up to about 3.5Hz in order to provide ride quality improvement, but neither of these functions moves the rudder in the absence of atmospheric disturbance or maneuver command input. Control surface oscillations without disturbance inputs would indicate limit cycling that is not permitted by design requirements.
I am not aware of any commercial flight control systems that have control surface command processing loops that run at frequencies higher than 100 Hz. Alternating current electrical power may is available with higher frequencies, but the fastest control surface command update loops run with frame times of 10ms or longer.