Distortion that is produced when higher harmonic components of the input audio signal sampled by a digital recording device, or generated within a digital sound source, lie above the Nyquist frequency. This happens when the sampling rate is less than twice the frequency of the signal being sampled. The effects of aliasing differ from some other types of distortion in that its pitch changes radically when the pitch of the intended sound changes.

Also called foldover.

See anti-aliasing filter.