Abstract: The present invention relates to a signal processing system for generating a nulling signal for attenuating a periodic noise component from an information signal. According to one aspect of the invention, the system includes two nested feedback networks. One network detects the phase angle and frequency of the noise component, and generates a nulling signal having a phase angle and frequency substantially equal to the phase angle and frequency of the noise component. The other network detects the amplitude of the noise component, and scales the nulling signal to have an amplitude substantially equal to the amplitude of the noise component. According to a further aspect of the invention, the system includes a combining network for attenuating the noise component by combining the information signal with the nulling signal. In this way, the invention preserves the high fidelity of the information signal except over a very narrow bandwidth, adjacent to the noise signal frequency.