fig8

Figure 8. EPG or EOS-based SSIs. (A) Working principle of EPG-based SSIs. The left part of (A): Adapted from Ref. [150], under CC BY 4.0 license; (B) EPG systems that can measure the contact between the tongue and the sensor. Adapted with permission from Ref. [52], Copyright 2022, ACM; (C) EOS systems for measuring contact and distance between the tongue and the sensor. Adapted from Ref. [151], under CC BY 4.0 license. EPG: Electropalatography; EOS: electro-optical stomatography; SSIs: silent speech interfaces.