Extended Data Fig. 3: Additional BCI speech synthesis performance metrics.
a. Mel-cepstral distortion (MCD) is computed across 25 Mel-frequency bands between the closed-loop synthesized speech and the target speech. The four subpanels show MCDs (mean ± s.d) between the synthesized and target speech for different speech tasks in evaluation research sessions. b. Human perception accuracy of BCI synthesized voice during mimed speech trials. 15 naïve listeners selected the transcript matching the synthesized speech from 6 possible sentences of the same length for each of the 58 evaluation sentences. Individual points on the violin plot show the average matching accuracy of each evaluation sentence (random small vertical jitter is added for visual clarity). The bold black line shows median accuracy (which was 100%) and the thin blue line shows the (bottom) 25th percentile.