"Jitter" is a term that is often used regarding digital audio, specifically the digital to analogue converter (DAC). This article aims to clarify the actual effects of phase noise on audio, and in this context presents a relatively novel way to measure.

"Jitter" can mean several things. Here we use the term to mean: phase error. Phase error is specified with respect to an offset frequency from a carrier i.e. clock.

The result of close-in phase error is a widening in the frequency domain of a pure tone. A pure tone is represented in the frequency domain as a thin line, having an amplitude at the frequency and no amplitude at any other frequency. Phase error spreads this line increasing the so-called line width.

A pure tone may be transmitted digitally to a DAC. An FFT spectrum may be taken at the analogue output of the DAC. My measuring the linewidth, the amount of jitter in the DAC is determined.