Four types of the stimuli used in this study.

<p>From the top to the bottom, the four types of stimuli are represented by the four lines: the 797-Hz pure tone, the 797-Hz pure tone smoothed by a 40-ms Hanning window, the missing fundamental harmonics with F0 = 797 Hz, and the Gaussian white noise. The left column shows the waveforms, and the right column shows the spectra.