# Exploring the Age Effects on European Portuguese Vowel Production: An Ultrasound Study
## 4 Discussion  
This study contributes to increasing knowledge on EP aging speech, providing an articulatory perspective of the effects of age in all oral vowels of the EP based on articulatory measures: TH and TA. The present study extends in many ways our previous pilot research by reporting articulatory data from more female speakers and by ensuring an inter-speaker comparison through the application of normalization procedures. In addition, the automatic method of contours tracing was improved. In general, the results of this articulatory study reveal that the highest point of the tongue tends to be higher for the older females and more advanced compared to the younger females (except the TH of the vowel [3]). The increase of the TH is in accordance with our previous acoustic study [16] of aging speech for EP. In other words, the tongue raising (higher TH) is correlated with a decrease in F1 [9; 56], which has been reported for  
Figure 10: Vowel articulatory cluster size of all EP vowels of two speakers in pVCv sequences (top) (**a**,**b**) and in isolated context (bottom) (**c**,**d**). Left side: young female (Y2); Right side: old female (O3). both EP [15, 16] and other languages [4, 5, 44, 77, 78] with aging. However, [PERSON] et al. [17] reported higher F1 values for vowels produced by older EP females. Regarding TA, the results indicate a tendency to tongue advancement in the older group, which is correlated with an increase in F2 [9, 56]. The tongue advancement observed for older females is not in line with our previous acoustic study [16], where a tendency for F2 decrease with aging occurred. Yet, some studies have reported vowel-specific changes with age and gender [5, 11, 17, 78, 79]. For EP, [PERSON] et al. [17] observed a trend for F2 decrease in back vowels and an increase in front vowels. Nonetheless, [PERSON] et al. [23] reported a reduction in tongue retraction on the vowel [a] in older adults, and they suggested that older speakers tend to hold the tongue in a more anterior position in the mouth than younger speakers. The authors [23] attributed this reduction in tongue retraction to a normal compensatory tongue motion, which is apparently due to alterations in the function of the suspensiony muscles of the tongue [80]. Beyond the observed displacement of the articulatory vowel space with age (i.e., more advanced) (see Figure 9), the vowels' space tends to be more reduced in younger than in older females. For EP, [PERSON] et al. [17] also reported an acoustic space that is more reduced for younger females. Although formant frequencies can be affected by other articulatory adjustments than the tongue movements, it would be interesting to study the acoustic-articulatory relationship of the data. Furthermore, [PERSON] and [PERSON] [44] suggested that the lowering of formants with age might be due to the lengthening of the vocal tract with aging, but in the present study, a tongue raising and a tongue advancement were observed for the older females. Additionally, the articulatory measures show great variability, as it can be observed by the different format of the individual articulatory vowel spaces and the vowel articulatory clusters. The comparison of the amount of variability within and across speakers in both age groups needs to take into account the fact that older speakers present less data, which does not allow drawing solid conclusions. In addition, there does not appear to be a direct relationship between speaker size (BMI) and the length of the tongue contour or the size of the acoustic triangle obtained. Concerning the vowel type, our results indicate a significant difference in tongue height position between the EP oral vowels examined, mainly between front and back vowels. As expected, for each block of vowels, the TH is higher for close vowels and lower for open vowels. An interesting observation is that for young females, the central vowels [v] and [a] show lower values and similar TH among each other, while for older females, the vowel [v] presents higher TH than vowel [a].