Similar and different tongue surface contours: intra-speaker controls in ultrasound analysis

Abstract

Ultrasound studies of speech production analyse differences in dependent variables reflecting the tongue surface’s location and shape. Inferential statistics distinguish theoretically-relevant from random effects, somewhat independently of the descriptive size of significant effects. Experimental designs induce measurable dependent changes by manipulating independent variables such as prosody, phonemic target, etc. This paper presents descriptive statistics quantifying holistically all 15 pairwise differences between six monophthongal long vowel phonemes of one variety of English, comparing these to experimental noise differences attributable to the use of two identical blocks of data collection in sequence. Eight speakers were recorded, using two different ultrasound systems, and analysed in AAA using both edge-tracking and DeepLabCut pose estimation. The smallest phonemic contrast (~2mm) was greater than the experimental noise (~1mm), and was well evidenced by AAA’s t-test of radial difference.