1. A method of detecting noise in an output provided by a sensor configured to modulate a carrier signal in response to the proximity of a stimulus, wherein the output is synchronously demodulated with the carrier signal and filtered by a demodulation filter having a demodulation filter bandwidth, the method comprising the steps of: sequentially applying the carrier signal to the sensor at a plurality of different frequencies comprising at least a first frequency and a second frequency to thereby produce at least a first output and a second output, respectively, wherein a difference between the first and second frequencies is less than the demodulation filter bandwidth; filtering an effect produced by the stimulus from at least the first and second outputs to thereby produce at least one filtered output; and determining noise contained within the at least one filtered output.