DC offset is a term used in signal processing to describe a mean amplitude displacement from zero. It is the mean amplitude of a waveform, and if the mean amplitude is zero, there is no DC bias. DC offset is usually undesirable when it causes clipping or other undesirable changes in the operating point of an amplifier. It can cause inaudible low-level distortion, audible clicks where audio sections are cut and pasted together, and can confuse level metering systems. DC offset can also cause damage to loudspeakers and headphones in some specific circumstances. In audio recording, a DC offset is an undesirable characteristic that occurs in the capturing of sound, before it reaches the recorder, and is normally caused by defective or low-quality equipment.
DC offset can be removed in real-time by a high-pass filter. For stored digital signals, subtracting the mean amplitude from each sample will remove the offset. As the DC-Offset signal' effectively has a frequency of 0Hz, a DC-Offset can be removed with a high-pass filter set to a few Hertz.
