Surface electromyographic control of speech synthesis

Individuals with very high spinal cord injuries (e.g. C1-C3) may be ventilator-dependent and therefore unable to support speech breathing. However, their facial musculature is intact, given that these muscles are innervated by cranial nerves. We developed a system using surface electromyography (sEMG) recorded from facial muscles to control a phonemic interface and voice synthesizer and tested the system in healthy individuals. Users were able to use five facial gestures to control an onscreen cursor and the phonemic interface. Users had mean information transfer rates (ITRs) of 59.5 bits/min when calculating ITRs using the number of phonemes selected. To compare with orthographic systems, ITRs were also calculated using the equivalent number of letters required to spell the selected word. With this calculation, users had a mean ITR of 70.1. Results are promising for further development and testing in individuals with high spinal cord injuries.