An instrument for the non-invasive assessment of lip function during speech

This paper describes the development of an instrument using infrared light as a non-invasive means of detecting lip opening, the extent of the opening and also the forward protrusion and backward movement of the lips during speech. The design criteria were to build a simple stand alone means of assessing lip function, which could also link to the group's commercially available Super Nasal-Oral Ratiometry System (SNORS+). SNORS+ allows objective assessment of the function and co-ordination of key articulators, with lip function previously monitored using a video camera. Synchronised tests were carried out using the new Lip Function Monitor and the video camera simultaneously, in order to verify that the signals produced related directly to the activity of the mouth. A small trial was then conducted to show that the system provides reproducible results throughout a range of 'normal' subjects. These subjects were of different gender and race to create a sample group within which there was a variety of lip sizes and face shapes. Technical aspects of the instrument and trial results are presented here. These suggest that the simple visual output and feedback of the instrument will prove useful in the assessment and management of speech disorders.