Effects of Amplitude Distortion upon the Intelligibility of Speech

In order to study the effects of amplitude distortion upon the intelligibility of speech, articulation tests were conducted with non‐linear circuits introduced into otherwise high‐quality audio systems. The non‐linear circuits represented basic types of amplitude distortion and provided controlled amounts of each type. The test results indicated that: (1) Non‐linear distortion of the kind commonly introduced when audio amplifiers are overdriven has very little detrimental effect upon intelligibility. Speech which has been subjected to sharp symmetrical overload—peak clipping—is almost perfectly intelligible, even if it has been stripped down to one‐tenth of the amplitude it would have had with linear amplification. (2) The extreme tolerance for peak clipping is matched by an equally marked intolerance for center clipping. Cutting out even a small fraction of the part of the speech wave nearest the time axis impairs intelligibility. (3) Insofar as the severity of their effects upon intelligibility is conce...