The Velotrace: A Device for Monitoring Velar Position

Abstract

This paper describes the Velotrace, a mechanical device designed to allow the collection of analog data on velar position. The device consists of two levers connected through a push rod and carried on a pair of thin support rods. The device is positioned in the nasal passage with the internal lever resting on the nasal surface of the velum and the external lever positioned outside the nose. The movements of the external lever reflect the movement of the internal lever as it follows velar movement and are recorded as an analog signal using an opto-electronic position-sensing system. Results of evaluation studies indicate that the Velotrace accurately reflects the relatively rapid movements of the velum during speech. Since the size of the velar port determines the oral or nasal nature of speech sounds, there has long been interest in studying the velopharyn-geal region (see Fritzell, 1969, for an extensive historical review). The various techniques used to study the velopharyngeal mechanism have examined a number of its dimensions, one result of which is the recognition that the size of the open velar port is reflected in the position of the velum, although velar position may also vary when the port is completely closed (see, for example , M011 and Daniloff, 1971; Henderson, 1984). These adjustments of velar position above the level at which closure occurs result from the anatomical relationship between the velum and the levator veli palatini (LVP) muscle. That is, since the superior attachment of the LVP muscle lies well above the level at which port closure is complete, increasing contraction of that muscle will continue to raise the velum even after the velopharyngeal port has been closed. As a result, changes in the vertical position of the velum throughout its range of movement may be con—