Sine-wave speech can be thought of as a sort of auditory illusion, a sensory edge case in which one’s experience has a clear “before” and “after” moment, like going through a one-way door.

You may click on any underlined ratio to hear a sound example. In each case, the fundamental frequency is 100 Hz, both carrier and modulator are sine waves, and the modulation index is swept from 0 to ...