A plurality of pulse signals (trigger signals) responsive to driving of a power plant are directly supplied to respective adaptive control circuits each having an adaptive digital filter for controlling components of periodic or semi-periodic vibrations and noises ascribed to related component parts of a vibration/noise source. Further, the adaptive control is performed while varying a sampling frequency in response to changes in parameters of operating conditions of the power plant. Optionally, a control signal from the adaptive digital filter is corrected for gain. Further, periodic signal-eliminating means is provided for determining a transfer characteristic of a system to which the adaptive control is applied, based on a residual component signal from the periodic signal-eliminating means, a random signal having a low amplitude level, etc.