Design and development of appliances for pressure electropalatography

Objectives: Electropalatography is an instrumental technique employed by phonetic scientists to investigate tongue behaviour during continuous speech. Widely recognised in clinics and laboratories around the world as a key diagnostic and treatment tool, the electropalatograph (EPG) has proved beneficial to many patients with speech disorders. Current systems enable information concerning the spatial and timing aspects of tongue contact with the hard palate to be communicated to the user via personal computer or by a portable acquisition and display system. These systems however do not provide any measure of contact pressure between the tongue and the palate. The aim of this research was to develop sensors and construction techniques for producing the first pressure-sensitive EPG. Method: A number of commercially available and custom made pressure sensors were evaluated for use in the construction of a pressure sensitive electropalatograph (PPG) device. The custom fabricated sensors developed were a miniature Hall effect pressure sensor (HEPS) combing a Hall-effect transistor and a Neodymium magnet bonded to a polyester cantilever to record pressure contacts with the tongue. The HEPS are incorporated into an individual acrylic appliance using modified dental processing techniques. Results: The commercially available sensors were unable to be adapted for intra-oral use due to lack of sensitivity or poor response times. The calibration results with the HEPS showed that the sensors recorded pressure levels expected to be experienced during speech. Trials on patients indicated that the PPG incorporating the HEPS provides spatial, timing and pressure aspects of contact between the tongue and palate in real-time. Conclusion: The construction of individual patient PPG appliances provides information in real-time that the therapist can use to illustrate to patients the nature of their impediment and assist them in developing correct sound production techniques. This research was supported by a NHMRC research development grant.