3.8 Summary and motivations
Although the articulation of English/r/has been widely studied inrhoticEnglishes, literature onnon-rhotic Anglo-Englishis distinctly lacking, as we observed inChapter 2. For one thing, there is a perception thatAnglo-English/r/is always produced with a tip-up tongue posture, although very little empirical evidence exists to back up this supposition. We first aim to fill this gap in the literature by accounting for the lingual gesture inAnglo-English/r/in a larger cohort of speakers than in previous articulatory studies onAnglo-English/r/(e.g., Delattre &
Freeman, 1968) usingUltrasound Tongue Imaging(UTI). UTI has been used by the linguistics community for phonetics research since the 1960s (Gick, 2002a) but has gained in popularity as a technique in the last 20 years (Kochetov, 2020). When an ultrasound transducer is placed under the chin, ultra-high frequency sounds waves emitted from a crystal contained within the transducer travel through the tongue body tissue and are reflected back from the tongue surface in the form of echos (Stone, 2005). The echos are then converted into two dimensional images of the tongue surface, either sagittally or coronally. The fact that ultrasound cannot image bone or air means that it can only provide images of the tongue surface, and not, for
93
example, images of the jaw, pharyngeal wall or palate.2 However, ultrasound is able to image the moving tongue in its near-entirety, producing high quality images, with good temporal resolution (30 fps or more) without causing discomfort or risk to the subject (Gick, Bernhardt, Bacsfalvi, & Wilson, 2008). As we are predominantly concerned with tongue shape, as opposed to its exact position in the vocal tract, UTI as a technique is well-suited to phonetic studies on English/r/and has been used in a variety of previous studies including Heyne et al. (2018), Lawson et al. (2013) and Mielke et al. (2016) to name a few.
Although the labial articulation of /r/ has received less attention than its lingual one, we predict that by varying the degree oflip protrusion, speakers may attain similar acoustic outputs across the different tongue shapes for /r/. Systematic trade-offs have already been observed for English/r/between the length of the front cavity and the length and size of the lingual constriction (Guenther et al., 1999) and a similartrading relationhas been proposed between thesublingual spacefor tip-up/r/and a more posterior palatal constriction for tip-down/r/
(Alwan et al., 1997). We predict that tip-down tongue shapes with negligiblesublingual space will compensate with increasedlip protrusionin order to maintain a large sized front cavity and therefore preserve a low third formant frequency in the resulting acoustic output.
To test to what extentlip protrusioncontributes to the production of/r/, we will present lip, tongue and acoustic data fromAnglo-Englishproductions in both non-hyperarticulated and hyperarticulated speech. By eliciting hyperarticulated productions, we predict that speakers will be forced to enhance the discriminability of/r/, which will result in the lowering of the third formant, the most prominent acoustic cue for English/r/. Iflip protrusioncontributes to the lowering of F3, hyperarticulated/r/may result in increasedlip protrusionand therefore produce even lower F3 values than those observed in non-hyperarticulated productions of/r/.
Lip protrusionwill be measured using profile lip camera videos synchronised with both the ultrasound and the acoustic signal.
The labial articulation seems particularly pertinent toAnglo-English/r/because labiodental variants are becoming increasingly common across England. Docherty and Foulkes (2001)
2The palate may be imaged indirectly by recording participants swallowing a bolus of water (Stone, 2005).
3.9. Research questions 95
defined a change in progress whereby the labial component ofAnglo-English/r/is ‘retained at the cost of the lingual articulation’ (p. 183). They hypothesised that this change may be a ‘function of the heavy visual prominence of the labial gesture’ (p. 183). Underlying these claims are the following premises: firstly, thatAnglo-English/r/is produced with a labiodental articulation even when accompanied by a coronal gesture, and secondly, that this labiodental gesture is visually prominent. We intend to verify both of these claims with two further experiments. In Experiment 2, we will provide a detailed phonetic description of the labial gesture inAnglo-English/r/by comparing it to that of/w/, whose articulation is unequivocally considered rounded. If/r/is labiodental, its labial posture should differ considerably from that of/w/. The labial postures of/r/and/w/will be studied from front and profile lip camera data taken in Experiment 1. In a third experiment, we will assess the visual salience of the labial gesture inAnglo-English/r/in a perception experiment. English participants will be presented with auditory-only, visual-only and congruous and incongruous audio-visual stimuli of/r/and/w/. If the labial gesture of/r/is labiodental and different to that of/w/, we expect the perception of/r/to be enhanced with visual cues. Subjects may even be able to distinguish between/r/and/w/from the visual cues alone if the visual difference is particularlysalient.
In incongruous audio-visual stimuli in which auditory/w/will be paired with visual/r/and vice versa,visual capturemay be anticipated if their respective visual cues are unambiguous and are moreperceptually salientthan the phonetic cues in the acoustic signal.
This thesis will not only contribute to the literature on the production of English/r/, but will have theoretical implications for the nature of speech perception in general, as well as for the role of visual speech cues in diachronic sound change.
3.9 Research questions
Given the observations gleaned from our review of the literature on the articulation of English /r/, on the phonetic implementation of labialisation and on multimodal speech perception more generally, the following research questions emerge:
1. Is the tip-up tongue shape typical of post-alveolar approximant/r/inAnglo-English?
(a) Is tongue shape subject to coarticulation with the following vowel as in other varieties of English?
2. How doeslip protrusioncontribute to the production ofAnglo-English/r/?
(a) Canlip protrusionenhance F3 lowering?
(b) Is there a relationship between the degree oflip protrusionand lingual articulation?
3. IsAnglo-English/r/produced with a labiodental articulation even in the cases where there is an observable tongue body gesture?
4. Is the labial posture forAnglo-English/r/perceptually salient?
Part IIpresents two production experiments which will address questions 1-3.Part IIIconcerns the perception of Anglo-English /r/and will therefore address the final research question, question 4.