Audio distortion arises from level-dependent nonlinearity in the device’s transfer function

Evidence

To understand what is going on, first consider what the real problem is: non-linear behavior in the audio device. This means that the relationship between the input signal and the corresponding output from the device changes with level. If the input increases by a certain percentage, the output should change by the same percentage, no more, no less. However, the percentage does change, 274. the shapes of audio waveforms are altered from a little to a lot. When we hear these distorted waveforms we notice that new sounds (distortion products) have been created. When the non-linear device is driven by a known, well-specified signal, we can measure how different the output is from the input, and obtain a measure of the magnitude of the distortion—for that specific signal. But, instead of measuring the nature of the non-linearity itself—as an input-to-output transfer relationship—we have chosen to try to quantify what it does to audio signals. Put a known signal into the device and spectrally analyze what comes out. — Toole, Floyd E, Sound reproduction- the acoustics and…, 988

Categorization

• DEFINE: Defines nonlinear behavior in audio devices as the input-output relationship changing with level, and explains why distortion products appear as new sounds.