An electronic process used to reduce noise levels in audio and video. In video, the most effective noise reduction is accomplished by digitising the video signal and carrying out a computerised pixel by pixel analysis of the data. In audio, the most effective systems employ an encode/decode scheme, performed before and after recording, such as the Dolby audio noise reduction system. Noise reduction can be performed on an existing audio signal using systems such as DNR (dynamic noise reduction) but are less effective because they also affect the audio signal.