# Exploring the Age Effects on European Portuguese Vowel Production: An Ultrasound Study
## 3 Results  
In this section, a summary of the main findings on EP vowel tongue configurations by age group is presented. In addition, some considerations about vowel context effect, and inter and intra-speaker differences are reported. Note that for some older speakers (see Table 3), there are no tongue contours available for some vowels, which does not allow a more comprehensive comparison between age groups to be carried out. In this section, the scaled US data are used (i.e., TA and TH obtained after normalization). The analysis starts with a brief inspection of the tongue contours. Thus, some examples of tongue contours for all vowels by context are presented in Figure 6 for one speaker (speaker Y1). Considering the articulatory measures, Figure 7 summarizes the TH (Figure 7a) and TA (Figure 7b) values obtained by vowel for each age group. In this first analysis, both contexts (vowels in pVCv sequence and isolated) are considered. In general, concerning TH, the older females showed higher values, except for vowel [\(\circ\)]. In general, the front vowels presented higher TH values, and the vowels [a] and [\(\circ\)] presented the lower values, mainly for the older females. For young females, the central vowels [\(\circ\)] and [\(\circ\)] showed similar TH, while for older females, the vowel [\(\circ\)] presented higher TH values than vowel [a]. In addition, old females presented identical values of TH for vowel [a] and [\(\circ\)]. Regarding TA, the lowest values (in module) were obtained for the old group. For both groups, the front vowels tend to present the lowest TA, and the vowels [\(\circ\)] and [\(\circ\)] revealed the highest TA values (in module). Variability tends to be higher in TA in comparison with TH values, mainly for young females (i.e., the variability of TA tends to decrease with age). To complement this initial analysis, the individual variability is also explored through the articulatory vowel space and the vowel articulatory cluster size by speaker and vowel context. Figure 5: Top: Illustration of normalization measures for TH (**a**) and TA (**b**). Bottom: Sustained vowels [a] contours of all speakers rotated (**c**) and scaled (**d**). Figure 8 represents the articulatory vowel space defined by scaled TA and TH values of the cardinal EP oral vowels ([a], [i], and [u]) for each speaker and vowel context (i.e., pVCv and isolated vowel). Each vowel is represented by the mean TH and TA. As four old females (O1, O2, O4, and O5) presented incomplete data, it was not possible to define the articulatory space of all speakers by vowel context. Furthermore, the young females also showed great variability in the shape of the articulatory vowel space. Concerning the vowel context, it can be observed that articulatory space tends to be smaller when vowels occur in pVCv sequences comparing with isolated vowels, namely for the speakers Y2, Y3, Y5, and O3. Figure 6: Example of one tongue contour by vowel for each context for speaker Y1. (**a**) pVpv context; (**b**) pVtv context; (**c**) pVkv context; (**d**) isolated context. Figure 7: Boxplots of TH (**a**) and TA (**b**) values by vowel and age group. Since our main goal is the study of age effects, in Figure 9, the articulatory vowel space of the two age groups is compared separately for each production context. The articulatory space was defined by the mean of the TA and TH values of the cardinal EP oral vowels for each speaker by vowel context. Figure 8: _Cont._  
The vowel articulatory space tends to be different, in shape and size, between the younger and older females in both contexts. Old females produced vowels with higher TH and a notable decrease (in module) of the TA (i.e., the highest point of the tongue contour tended to be more advanced). Consequently, these results are in line with some of the observations made above. The vowel articulatory space differences observed between both contexts is more pronounced for the young females.