A. Rhythmic noise-vocoded speech sounds, consisting of five one-syllable words, were presented so that the p-center of all syllables (dashed lines) fell at one of eight different phases of simultaneously applied tACS. After each trial, participants selected images that correspond to the second, third and fourth word they thought to have heard, with eight possible options for each word. B. Electrode configuration in Experiment 1 (unilateral) and 2 (bilateral). For both configurations, connector positions are shown in black. For the bilateral configurations, parts of the outer electrodes covered by isolating tape are colored black. C. Blocked design used in both experiments. Participants completed 4 x 5 runs, with two possible run orders as shown here and described in detail in Section Experimental Design. D. Proportion of 16-channel vocoded speech used to construct vocoded stimuli (for which 16- and 1-channel speech were mixed; see Section Stimuli), separately for each participant and the four adaptive runs in the two experiments.