Non-linear

Overview

The term "distortion" is used broadly to describe the result of audio passing through a non-linear process.

Basics

Some examples are clipping, analog tape saturation, "hard limiting" with very fast attack and release times, or distortion caused by transformers or tubes. Other examples of distortion in analog audio systems are harmonic and intermodulation distortion. Harmonic distortion (as the name implies) refers to the generation of harmonics of the input signal by the audio system. Intermodulation distortion is typically caused by an interference signal interacting with the input signal and is not harmonic in nature; making it my more audible at lower levels than harmonic distortion.

Non-linear processes in digital audio equipment can also cause distortion; and like intermodulation distortion, tends to be not harmonic in nature and also more audible at much lower levels than harmonic distortion as a result. On example of this type of distortion is the effect of jitter in clocking of conversion.