“…In addition to current speech recognition applications, silent speech recognition can also be applied to communications involving people with speech disorders, in noisy environments, and when greater security is required [2]. To enable speech recognition without sound, a variety of sensors have been utilized, such as electromyography (EMG) [3,4,5], electromagnetic articulography (EMA) [6,7,8,9], non-audible murmur (NAM) microphones [10,11,12], ultrasound transducers with video cameras [13,14,15,16], and ultrasound Doppler sensors [17,18]. …”