Neck and face surface electromyography for prosthetic voice control after total laryngectomy

Abstract

The electrolarynx (EL) is a common rehabilitative speech aid for individuals who have undergone total laryngectomy, but they typically lack pitch control and require the exclusive use of one hand. The viability of using neck and face surface electromyography (sEMG) to control the onset, offset, and pitch of an EMG-controlled EL (EMG-EL) was studied. Eight individuals who had undergone total laryngectomy produced serial and running speech using a typical handheld EL and the EMG-EL while attending to real-time visual sEMG biofeedback. Running speech tokens produced with the EMG-EL were examined for naturalness by 10 listeners relative to those produced with a typical EL using a visual analog scale. Serial speech performance was assessed as the percentage of words that were fully voiced and pauses that were successfully produced. Results of the visual analog scale assessment indicated that individuals were able to use the EMG-EL without training to produce running speech perceived as natural as that produced with a typical handheld EL. All participants were able to produce running and serial speech with the EMG-EL controlled by sEMG from multiple recording locations, with the superior ventral neck or submental surface locations providing at least one of the two best control locations.

Figure 1. Electrode Placement

The left panel shows example sEMG electrode locations as placed on participant S3 during experimentation. The right panel shows a schematic of the expected residual muscles after total laryngectomy superficial to sEMG electrodes, depicted on the right side only. Absent from this depiction is the platysma, which is located in the subcutaneous tissue of the neck.

Figure 2. sEMG Electrode Recordings

An example of the audio and raw sEMG data collected as a participant counted aloud using a typical EL. Traces indicated by EMG1 – EMG7 refer to sEMG collected from the seven electrode positions indicated in Figure 1.

Figure 3. Example Screenshot of sEMG Biofeedback

An example of the real-time visual feedback of the RMS sEMG and EMG-EL threshold settings is shown. The black line shows the sEMG envelope used to control the onset and termination of the EMG-EL. The two red lines specify the settings for onset threshold and offset threshold. The blue shading indicates time periods during which the device was activated.

Figure 4. Serial Speech Performance

The serial speech performance (average of the percentage of appropriately voiced words and the percentage of appropriately unvoiced pauses) is shown for each participant at each of the seven electrode positions.

Figure 5. Participant sEMG during Serial Speech

The difference between words and pauses in the percent above baseline RMS sEMG from each recording location during serial speech using a traditional EL (labelled as “Initial”) and during use of the EMG-EL with visual feedback (labelled as “During Feedback”) for each participant. Electrode positions for which each participant achieved at least 80% serial speech performance using the EMG-EL are indicated with background shading in grey.

Figure 6. Visual Analog Scale Perceptual Results

The results of the visual analog scale assessment are shown graphically, separated by speech task (“Sentences” and “Spontaneous”). Blue circles indicate average visual analog scale scores with error bars extending +/− one standard deviation. On this scale, normal natural speech is located at 0.