Evaluation of a non-invasive vocal cord vibration switch as an alternative access pathway for an individual with hypotonic cerebral palsy – a case study

Abstract

Purpose. A novel non-invasive vocal cord vibration switch for computer access was designed for an individual with hypotonic cerebral palsy. An evaluative case study was performed to compare the new device to an existing commercially available voice-activated switch in terms of sensitivity, specificity, speed, and user fatigue.

Method. The participant wrote pangram sentences with the two switches over 4 days with two sessions each day (morning and afternoon). The order of the switches was alternated and a new sentence was used each day. The user's perceived level of exertion was noted before and after each task and activation errors were logged for performance analysis. After using the device for 2 months, a qualitative survey was administered with the participant and his educational assistant.

Results. The vocal cord vibration switch outperformed the voice-activated switch in terms of sensitivity (p < 10⁻⁴, t-test), speed (p < 10⁻³), and user-perceived exertion (p < 10⁻⁴). Qualitatively, both the participant and his educational assistant were more satisfied with the proposed switch relative to his existing solution.

Conclusions. The results of this study show that the vocal cord vibration switch provides a promising new alternative for individuals with severe and multiple disabilities who are able to hum or produce vocalizations.

Keywords:

• Voice switch
• vocalization response
• augmentative and alternative communication (AAC)
• aided communication
• computer access

Acknowledgements

We thank Ka Lun Tam and Pierre Duez for their invaluable technical support. This research was funded by the Canada Research Chairs Program, the WB Foundation, and the Remad Foundation.