ICPhS XVII Regular Session Hong Kong, 17-21 August 2011

MRI INVESTIGATION OF

Saeed Shar & John Ingram

School of and Cross Cultural Studies; University of Queensland, Brisbane, Australia [email protected]; [email protected]

ABSTRACT observe if these two parameters provide an articulatory basis for classifying gutturals into a Five native speakers of Assiri Arabic were imaged natural class [6]. Arabic do using magnetic resonance imaging (MRI) during not have a single common articulatory feature their production of gutturals. These Arabic back identifying them as a natural class except sharing consonants are characterized by articulation in the the same region of articulation, the pharynx. pharyngeal region that extends between uvular and Although, the [ʔ] and [h] larynx. The aim of this experiment is to examine lack constriction in this region, yet they are also pharyngeal width and larynx height in production classified as guttural ([6, 7]). of these consonants and observe if these two This experiment will identify pharyngeal parameters provide an articulatory basis for constriction by measuring change in pharyngeal classifying gutturals into a natural class in the width during articulation of each . feature geometry. Keywords: gutturals, magnetic resonance imaging 2. METHOD (MRI), Arabic, pharyngeals, articulatory feature 2.1. Subjects 1. INTRODUCTION Five subjects participated in the experiment. Subjects were not scanned in the same session. The Arabic gutturals are a group of consonants that first subject (the first author) was scanned in a trial share the pharynx as a . They session which was used to establish the protocol are classified into three subgroups: and measurement procedures while the other four Glottals subjects were scanned afterward in Wesley [ʔ] &[h] as in ʔum & hum “mother”, “they” hospital in Brisbane, Australia. All of the subjects Pharyngeals lived the majority of their lives in Saudi Arabia. [ʕ] &[ħ] as in ʕali & ħali “high” , “sweet” They had moved to Brisbane where they resided Uvulars for 1-2 years at the time when this experiment was []&[ʁ] as in ali & ʁali “empty” , “expensive” conducted. Subjects’ age range was between 25-35 years. All subjects were native speakers of Arabic Since they share the pharyngeal cavity as a and spoke the Assiri dialect which is spoken in the place of articulation, [6] suggests granting southern region of Saudi Arabia. gutturals the feature [pharyngeal] (where its place feature is broadly interpreted to extend to 2.2. Stimuli constriction in the pharynx and larynx). This hypothesis is built upon some phonological The target sounds to be examined in this study are evidence that demonstrate similarity between the set of gutturals; [ʔ] [h], [ħ], [ʕ], [] and [ʁ]. gutturals in Arabic. This hypothesis was Also, oral consonants [s], [t], [ð] and [d] were previously investigated using techniques such as tested to provide comparative measurements X-ray [5]. Also, they were investigated using between gutturals and this group of coronal endoscopy [7] and [2-4]. However these consonants. The reason for choosing this group of consonants have not been previously investigated oral consonants is that they have equivalent using MRI. emphatics that have secondary articulation in the Pharyngeal width and larynx height are pharyngeal region while these plain consonants considered two parameters in the articulation lack this constriction and are the most appropriate back consonants. The aim of this experiment is to oral consonants that can be compared with examine the role of pharyngeal constriction and gutturals. laryngeal height in the production of gutturals and

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ICPhS XVII Regular Session Hong Kong, 17-21 August 2011

2.3. Apparatus vertebra. The vertical movement of the larynx was observed by measuring the change of distance The static MR images were obtained using a between the two vertebral reference points and the Siemens 2.0 T Signa magnet; 6-mm thickness horizontal line. This change of distance was sagittal slices were captured using the fast spin- labeled Laryngeal height. Elevated laryngeal level echo technique with the following parameters: was characterized with a positive sign while a time repetition (TR) = 52 ms, time echo (TE= 4.8 depressed laryngeal level was characterized with a ms, Flip Angle (FA) = 20 degree, field of view negative sign. (FOV)= 200 Phase: 81.3 and Bandwidth = 176 hx The second variable that was observed from the /pixel. Acquisition times were 11 seconds and the MRI images was pharyngeal width on two levels; number of slices was 6 per acquisition. This at the level of root (pharyngeal width) and relatively long acquisition time represents a at the level of epiglottis (epiglottal width). In order practical limitation on the use of static MRI in to measure these parameters, two reference points research. were identified on the front surfaces of the second The static MRI was chosen for this experiment and third vertebrae, exactly above the vertebral rather the dynamic one for couple of reasons. The cartilages that are located on the underside of each main one is that the dynamic MRI is composed of the two vertebrae. Change in pharyngeal width can single images from different times of the be calculated from horizontal movement of the production of a sound, and these images are put tongue root and the epiglottis. In addition to these together to make an animation. Since the fixed reference points, the movement of the tongue individual images have low quality resolution, root and the epiglottis were determined by drawing dynamic MRI cannot be used to find exact vertical lines on their back surfaces. The distance dimensions of pharyngeal width and larynx height. between these vertical lines and the two front Additionally, dynamic MRI was not available at vertebral reference points can be measured during the University of Queensland at the time this study ‘rest position’ (supine position in MRI without was conducted. speech) of each subject and during production of 2.4. Method of MRI image capture and data target consonants. analysis Figure 1: Measuring larynx height and pharyngeal constriction width: 1. A long horizontal line represents In this experiment, 11 seconds was the acquisition larynx height in a straight level; a short vertical line time to record 6 images, 1.83 second per image. In represents the total distance between two reference an effort to overcome the difficulty caused by long points. 2. A long vertical line is used to measure capture times required for static MRI imaging, all pharyngeal width during the horizontal movement of subjects were trained to maintain a static target the tongue root. posture for the production of each sound. Target sounds were printed and distributed among the subjects. During production of sounds, subjects were trained to hold the initial position of each target sound for 11 seconds which is the necessary time for acquiring images. These training sessions were repeated until the investigators became sure that all subjects were aware of what they were going to do during the time of MRI scanning. In this experiment, we are concerned with two variables: larynx height and pharyngeal constriction. As shown in Figure 1, laryngeal height is determined by an extended horizontal line which was drawn on the top surface of the arytenoid cartilage. This horizontal line intersected 3. RESULTS a vertical line linking two stable reference points. Results were plotted in Figure 2, which shows in The first stable reference point is on the upper millimeters the average change of pharyngeal surface of the fifth vertebra and the second point is width, epiglottal width and laryngeal height with specified on the lower surface of the same respect to the resting position of the articulators of

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ICPhS XVII Regular Session Hong Kong, 17-21 August 2011

each subject. To evaluate the three parameters - A second ANOVA was conducted to pharyngeal width, epiglottal width and laryngeal investigate the role of subject and epiglottal width height - a series of two-way ANOVAs were in differentiating these two types of consonants. conducted. One aim of these ANOVAs was to The results showed the subject factor was investigate whether these parameters have a significant (p = 0.036) there was a highly significant role in distinguishing gutturals from significant main effect for epiglottal width (p = plain consonants or not. Also, the subject factor 0.001). The significant effect for subject is was investigated for individual differences and, considered small when compared with the lastly, the interaction between the three parameters significant role of epiglottal width. There was no and the Subject factor was examined to observe if interaction between subject and epiglottal width (p there were any interaction effects involved. = 0.90). Figure 2: Changes (shown in millimeters) in The third ANOVA was conducted to pharyngeal width, epiglottal width and laryngeal investigate subject and laryngeal level. This two- height. Minimized pharyngeal width and elevated way ANOVA also investigated whether there laryngeal level was granted positive value while was any interaction between them. Here, it can widened pharyngeal and depressed laryngeal level was be seen that the subject factor was highly granted negative value. significant (p = 0.00000019). This finding may be ascribed to individual differences between subjects who differ physiologically so that the horizontal levels of the larynx naturally are different. Larynx level is also significant (p = 0.03), however, this effect is small in comparison with the highly significant effect of subject. The ANOVA results show a significant interaction between subject and the laryngeal (p = 0.003). This interaction was plotted in Figure 3. Figure 3: Interaction between subject factor and laryngeal level during production of gutturals and plains (oral consonants).

The first ANOVA was carried out to investigate the role of subject and pharyngeal width in differentiating between gutturals and oral plain consonants. The results show the subject factor is significant (p = 0.04), and that pharyngeal width has a highly significant role in distinguishing To further verify the ANOVA results, post-hoc gutturals from plain consonants (p = 0.0003). tests were carried out. These tests indicated that, Although there is a significant main effect of of the three parameters, pharyngeal width plays the subject, its magnitude is considered small most significant role in distinguishing the gutturals compared with the high significant role of (p = 0.0006). Epiglottal width is also significant, pharyngeal width. There was no interaction however it is less significant pharyngeal width t (p between subject and pharyngeal width (p = 0.56). = 0.0019); and laryngeal level is not significant (p = 0.1573).

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4. DISCUSSION 5. CONCLUSION Generally, it can be said that pharyngeal and To conclude, it can be said that group of gutturals, epiglottal widths are distinctive articulatory with the exception of the glottals, have different gestures of gutturals. Conversely, laryngeal height constrictions in the pharyngeal region. Pharyngeals is a gesture that does not correlate directly with the have constriction in the lower part of the pharynx; production of gutturals. uvulars have constriction in the upper part of the During the production of the glottal stop [ʔ] and pharynx. Furthermore, the laryngeal level is highly fricative [h], there is no clear constriction point in influenced by the natural physiological position of the pharynx even though they are produced with a individual subjects. At the same time, Average narrower pharyngeal width and retracted epiglottis. findings of MRI suggest that laryngeal height is a These findings support the results of previous variable that controls the of studies by [2, 4] and [7] which found that the oral gutturals; however this articulatory feature cannot consonants, [s] and [k], are produced with a be considered as a phonetic basis to distinguish narrower pharyngeal width than the glottal gutturals as a natural class of sounds. consonants [ʔ] and [h]. In contrast, these studies do not agree with [5] who explained retraction of the 6. REFERENCES epiglottis towards the pharyngeal wall observed in [1] Bukshaisha, F. 1985. An Experimental Study of Some one X-ray image as a constriction formed to Aspects of Qatari Arabic, Ph.D. dissertation, University produce the glottal stop [ʔ]. This claim is perhaps of Edinburgh. [2] Esling, J.H. 1996. Pharyngeal consonants and the supported by observations of a similar retraction of aryepiglottic sphincter. Journal of the International the epiglottis toward the pharyngeal wall during Phonetic Association 26, 65-88. the production of the plain alveolar fricative [s]. [3] Esling, J.H. 1998. Laryngoscopic analysis of pharyngeal A raised larynx is a noticeable gesture during articulations and larynx-height quality settings. the production of pharyngeals, as previously Proceedings of the 5th International Conference on Spoken Processing Sydney, ASSTA 2, 543- observed in studies by [1] and [7]. The pharyngeal 546. [ʕ] is characterized by the maximum [4] Esling, J.H. 1999. The IPA categories “pharyngeal” and elevated larynx among the group of gutturals while “epiglottal”: Laryngoscopic observations of pharyngeal the pharyngeal fricative [ħ] is characterized with articulations and larynx height. Language and Speech 42, 349-372. the maximum pharyngeal constriction. [5] Hess, S. 1998. Pharyngeal Articulations. Ph.D. The [ʁ] and the voiceless dissertation, University of California, Los Angles. uvular fricative [] are produced with constriction in [6] McCarthy, J. 1994. The phonetics and phonology of the uvular region due to retraction of the tongue semitic pharyngeals. In Keating, P. (ed.), Phonological Structure and Phonetic Form: Papers in Laboratory dorsum towards the uvula. The constriction in this Phonetics. Cambridge, Mass: Cambridge. region is accompanied by minimized pharyngeal [7] Zawaydah, B.A. 1999. The Phonetics and Phonology of width. Both uvulars [ʁ] and [] are articulated with Gutturals in Arabic. Ph.D. dissertation, Indiana almost equal pharyngeal width; however the uvular University, Indiana. [] is produced with more retracted epiglottis and higher laryngeal settings. MRI data show that laryngeal height does not correlate directly with production of gutturals; however it relates mostly to the physiological natural level of the laryngeal structure Figure 3. At the same time, the average findings of MRI data agree with Esling’s findings ([2-4]) which suggest that is associated with larynx height in the articulation of pharyngeal and stops while a lowered larynx is associated with in production of the pharyngeal fricative. Esling suggests that larynx height controls the manner of articulation of back consonants by permitting the epiglottis to move differently to the posterior wall of the pharynx.

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