Zipper Noise

A rapid stepping effect that sounds like a type of distortion. It’s sometimes audible when changing parameters in a digital device, especially things like filters, delay times, and gain settings. It is an artifact caused by the quantization of digital control signals for various parameters. In digital controls the changing values are spaced apart and stepped, whereas in analog they are continuous. It becomes noticeable when the resolution of the digital control signal being used to change the parameter is too coarse to avoid audible stepping between successive levels.