Nollmedelvärde

Nollmedelvärde, often translated as zero-mean or zero-average, is a statistical and signal processing concept referring to a signal or a set of data whose average value is zero. This means that over a given period or across a dataset, the sum of the positive values is equal to the sum of the negative values, resulting in a net average of zero.

Signals with a zero-mean property are common in various scientific and engineering disciplines. For instance, in audio processing, the waveform of a sound signal typically has a zero mean. If a signal consistently deviates from zero in one direction, it can introduce undesirable artifacts or biases in subsequent processing. Many signal processing algorithms, such as those used in image compression or noise reduction, assume or require the input signal to have a zero mean.

Achieving a zero-mean signal often involves a pre-processing step called DC offset removal or mean subtraction. This involves calculating the average value of the signal over a specific window or the entire dataset and then subtracting this average from each data point. This transformation does not alter the variability or the shape of the signal but shifts its baseline to zero. In some contexts, a signal that is not zero-mean might be referred to as having a DC component, which is then removed to obtain the AC component that has a zero mean. This concept is fundamental for understanding and manipulating various types of data and signals.