fig9

Figure 9. PMA or EMA-based SSIs. (A) Working principle of PMA-based SSIs. The left part of (A): Adapted from Ref. [4], under CC BY 4.0 license; (B) PMA system for SSIs. The PMA headset and one magnet in the left part of (B): Adapted from Ref. [158], under CC BY 4.0 license. The portable device and multiple magnets in the right part of (B): Adapted from Ref. [4], under CC BY 4.0 license; (C) Working principle of EMA-based SSIs. The left part of (C): Adapted from Ref. [159], under CC BY 4.0 license. Signals in the right part of (C): Adapted from Ref. [160], under CC BY 4.0 license; (D) EMA system for SSIs. The wave system in the left part of (D): Adapted from Ref. [158], under CC BY 4.0 license. The rest of (D): Adapted from Ref. [159], under CC BY 4.0 license. PMA: Permanent magnetic articulography; EMA: electromagnetic articulography; SSIs: silent speech interfaces.