System and method for controlling learning period for adaptive noise cancellation

A data acquisition system coupled to a mains power source that provides cyclical periods of power, comprising:

• a test probe configured to be coupled to a subject;
• an analog to digital converter that converts a signal from the test probe to samples;
• a noise replica generator that generates estimates of noise in the samples;
• a noise removal block that removes from each sample an estimate of noise therein;
• a period detector that detects starts of first and second cyclical periods of the power provided by the mains power source and generates a signal indicating each such start, wherein the second cyclical period precedes the first cyclical period;
• a stimulus generator that monitors the signal generated by the period detector and applies stimulation to the subject during the first cyclical period of the power, does not apply stimulation to the sample during the second cyclical period of power, and generates a gating signal during the second cyclical period of the power;
• and
• a gating module that monitors the gating signal and determines when the subject is undergoing stimulation, wherein the gating module provides the samples to the noise removal block and not to the noise replica generator when the subject is undergoing stimulation, and provides samples to both the noise replica generator and the noise removal block when the subject is not undergoing stimulation.