A Cephalometric Study of Velar Height as a Function of Voice Fundamental Frequency in the Normal Speaker

Abstract

An understanding of velar activity during vowel utterance has resulted from the use of several methods of study and observation. Both acoustic and perceptual methods have been used to describe velar activity. Acoustic characteristics have been related to nasality. Perceptual studies have enumerated variation in judged severity of nasality. Cinefluorographic techniques have been used to investigate the effects of vocal effort and fundamental frequency on velar movement. Intra-oral photographic techniques have also been employed to understand this relationship. Due to conflicting reports from the several techniques, the present study was undertaken to utilize a new approach of still cephalometric radiographs during sound production. The purpose of the present study was to use a cephalometric procedure to investigate velar height and velopharyngeal gap as a function of fundamental frequency in normal subjects. Four levels of fundamental frequency (10%, 25%, 50%, and 75% of the subject's total vocal range) at constant vocal effort were performed by 11 normal adult males on sequences of the vowel /a/. Each subject was carefully trained to utter the vowel sound at each of the four pitch levels as computed by a Honeywell Visicorder. A v-u meter indicated constancy of vocal effort. A lateral cephalometric headplate was taken under each of the four vocal pitch conditions. Velar height and velopharyngeal gap were measured by means of an acetate tracing from each headplate. The measurements were submitted for statistical interpretation. Major findings included:

Tracings and measurements could be done accurately. Vocal fundamental frequency productions were accurate. Vocal effort could be maintained constant. No significant difference between pitch levels for either velar height or velopharyngeal gap was indicated. Highly significant differences in measurements of velar height and velopharyngeal gap were noted between subjects. No significant correlation between 75% and 10% pitch levels was indicated by a Pearson product-moment correlation. A significant correlation between 25%, 50% and 75% levels was evidenced.