(A) Segments from each condition (nat, 8-channel, and 1-channel) in the time domain (see also Video 1). Overlaid is the amplitude envelope of each condition. (B) Spectrogram of the speech samples from (A). The effect of spectral vocoding on the fine spectral detail in all three conditions. (C) The superimposed amplitude envelopes of the samples for each condition are highly similar, despite distortions in the fine spectral detail. (D) Behavioural performance on the comprehension statements reveals that comprehension is unperturbed in the nat and 8-channel conditions, whereas the 1-channel condition elicits chance performance. (E) Coherence spectrogram extracted from bilateral temporal sensors reveals a peak in cerebro-acoustic coherence at 7 Hz, across groups and conditions. The shaded area depicts the frequency range of interest in the current study. The topography shows the spatial extent of coherence values in the range 4–9 Hz. Enhanced coherence is observed selectively in bilateral temporal sensors. (F) Source reconstruction of the raw coherence confirms that cerebro-acoustic coherence is strongest in the vicinity of auditory cortex, bilaterally, extending into superior and middle temporal gyrus. (G) Statistically thresholded maps for the contrast between natural and 1-channel vocoded speech show an effect of intelligibility (p<0.05, FWE-corrected) in right STG. (H) Enhanced envelope tracking is observed for EB versus SI in a bilateral parieto-occipital network along the medial wall centred on Precuneus (p<0.05, FWE-corrected). (I) The statistical map shows the interaction effect between blindness and intelligibility: Early blind (EB) individuals show enhanced synchronization during intelligible (nat) versus non-intelligible speech (1-channel) as compared to SI in right calcarine sulcus (CS) (p<0.005, uncorrected). (J) Boxplots for three regions identified in the whole-brain analysis (top panel, STG; middle panel, parieto-occipital cortex; bottom panel, calcarine sulcus).