(1) In recording and reproducing, the unwanted disturbance within a useful Frequency band, independent of whether or not a signal is present. The signal is not to be included as part of the disturbance. (2) In receivers, the random oscillation in the absence of signal Modulation on the carrier. ambient oscillations detected, measured, or recorded with the signal become part of the background noise. Included in this definition is the Interference resulting from Primarypower supplies.