University of Aizu, Graduation Thesis. March, 2012 s1160031 1

Articulatory Setting of the Tongue for Eastern VersusWestern JapaneseAtsushi Ueno s1160031 Supervised by Professor Ian WilsonAbstractThe underlying setting of the articulators in speechis called the articulatory setting. This setting variesacross languages and dialects. This research focuseson Japanese articulatory setting of the tongue, es-pecially the differences between eastern and westernJapanese. The method of this research is mainly col-lecting ultrasound data of subjects, and analyzing thetongue’s center of gravity using software such as Ed-getrak and MATLAB. Edgetrak is used for getting thecoordinates of the tongue surface and MATLAB isused for calculating the center of gravity. The results ofour analysis show that the distance from the center ofgravity of the tongue to the top of the ultrasound probeis greater, on average, for western Japanese subjectsthan for eastern Japanese subjects. In other words,the rest position of the tongue is higher for westernJapanese than it is for eastern Japanese. In addition,we found an effect of the preceding vowel on the restposition of the tongue.

1 IntroductionEven within the same language, there are different fea-tures of speaking (intonation, articulation, etc.) de-pending on the dialect. Of course, Japanese is no ex-ception, and the differences between those features areclear between eastern and western Japanese dialects.For example, in many eastern Japanese dialects, thepitch gradually declines toward the end of a declarativesentence. On the other hand, speakers of some westernJapanese dialects tend to raise the pitch of the wordat the end of a sentence. Thus, there are such distinc-tions between eastern and western Japanese. So, theinfluence of such distinctions on each articulator needsto be measured. It is hypothesized that these differentways of speaking (i.e., different dialects) have differ-ent articulatory settings. If speakers are aware of howthe settings differ across languages and dialects, it mayhelp them when they are acquiring a new language.

With the improvement of measurement techniquessuch as ultrasound, researchers have been able to studyand measure the articulatory setting of various lan-

guages. According to a study of the articulatory settingof French and English monolinguals and bilinguals [1],tongue tip height of English speakers was higher thanFrench speakers during speech rest position (betweenutterances). Furthermore, English speakers tended toprotrude upper and lower lips more than French speak-ers during rest position. As just described, it is ap-parent that there are differences between articulatorysettings across languages.

One of the key things that cannot be overlooked ishow we define the underlying tongue position (i.e.,the articulatory setting). The research noted above[1] focused on the tongue tip height from the ultra-sound probe during rest position between utterancesas the method of finding out articulatory setting of thetongue. One problem with that method is the difficultyin finding the alveolar ridge in the ultrasound images.If one cannot find consistent bone points in the ultra-sound image, it is difficult to consistently measure thesame point on the tongue. So, in this research, we con-sidered the center of gravity as the definition of tongueposition. The reason why we use center of gravity ofthe tongue is because it is easier to see the movementof the whole tongue and how different tongue rest po-sitions are affected by neighboring vowels.

Considering western Japanese, especially the peopleliving in Kansai, one feature of speaking is that assim-ilation in diphthongs, such as “sugee” for “sugoi” or“samii” for “samui” hardly occurs. On the other hand,eastern Japanese, especially the people living in Tokyo,often use assimilation of diphthongs like the above [2].In general, it is known that the tongue position whenJapanese pronounce long vowels such as “い [i]” and“え [e] ” becomes more forward [3]. Consequently, itis hypothesized that eastern Japanese tongue rest po-sition and its center of gravity would be slightly moreforward than western Japanese because they use longvowel frequently such as “い [i]” and “え [e]”.

Thus, the topics we cover in this research are as fol-lows: 1) Finding the difference between articulatorysetting of the tongue for eastern and western Japanese.2) Finding the effect of each preceding vowel on thetongue’s rest position.

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2 Method2.1 ParticipantsWe collected data from nine western Japanese subjects.We used the eastern Japanese data that had been col-lected for earlier research [4]. It is difficult to definethe border of eastern and western Japan because thereare many methods of how to divide up Japan dependingon the viewpoint (e.g. culture, food and language). Inprinciple, we need to decide that border from a linguis-tic point of view. Even that, though, is very difficultto do because there are so many dialects of Japanese.However, in this case, we defined Tohoku and Kantoas eastern Japan and Chubu, Kinki, Shikoku, Chugokuand Kyushu as western Japan. It is possible that one ortwo eastern subjects spoke with a western dialect, butnot likely. All the western Japanese participants wereundergraduate students and have the dialects of eachrural area.

2.2 StimuliThe stimuli that we used for data collection were shortJapanese sentences identical to those used in the east-ern Japanese data collection [4]. We did three trialsof 30 Japanese sentences each; each trial had the sameset of 30 sentences rearranged in random order. Oneexample of a stimulus sentence is 千葉さんは音痴(Mr.Chiba is tone deaf). Because we suspected thatarticulatory setting is affected by preceding and fol-lowing consonants and vowels, we controlled for thesound at the beginning and end of sentences (to bal-ance the numbers of each consonant and vowel). So,we used six PowerPoint slides for each sentence-finalvowel, i.e. あ [a],い [i],う [W],え [e],お [o], to bal-ance the numbers of vowels. Stimuli were displayedon a Mac laptop and presented to subjects in automaticPowerPoint presentation, one sentence at a time.

2.3 ApparatusUltrasound (Toshiba Famio 8) was used to record themovement of the tongue in speech. Two video cameras(JVC GZ-HD7 from the front and Panasonic HDC-TM750 from the side) were used to record the headmovement of each subject. The front image of the facewas collected for future analysis of lip movements.Two Mac computers (iMac and MacBook Pro) wereused, the latter for displaying stimuli, and the formerfor recording the combination of ultrasound movie andaudio. A microphone (Shure SM10A) was used torecord the subject’s utterances. An audio and visual

mixer (Canopus ADVC-700) combined the ultrasoundmovie and the audio of each subject. A specially madehelmet and glasses that I constructed were used totrack four pink dots that were attached to those and wecould determine the angle between the line of the up-per two dots and that of the lower two dots. Also, fourlip markers were used to measure the subject’s mouthaperture. Two halogen lights (LPL VL-1300+PRO4)were used to shine light on the subject indirectly usinglight reflectors.

Figure 1: Helmet holding ultrasound probe and glassesused for data collection

2.4 Procedure2.4.1 Data CollectionWe collected western Japanese data to compare withpreviously collected eastern Japanese data [4]. First,we explained to the subjects that what they should dois simply read some sentences, and we hid the purposeof this research from the subject (so as not to influencetheir usual speaking pattern). Second, the subject hadto put on some equipment (e.g., helmet, lip markers,etc.), as discussed above. Third, we checked whetherall equipment was working normally or not. Beforedisplaying stimuli, the subject had to swallow so thatwe had a record of where the palate is (for future re-search). Finally, we struck a clapper and displayed thestimuli.

2.4.2 Data AnalysisRest position frame For western Japanese, first ofall, we had to look for the rest position frame of thetongue from the ultrasound movie. The definition ofrest position was the condition in which the motionof the tongue stopped for more than 0.3 seconds (10frames) between each pair of sentences. The number

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of possible rest position frames for each subject was 30because one trial that we used for stimuli had 30 sen-tences. However, there were only from 5 to 15 usablerest position frames per subject because of swallowing,etc. With 3 trials (90 sentences) per subject, we couldcollect about 30 suitable rest position frames per sub-ject. For eastern Japanese, the same method [4] wasused.

EdgeTrak To calculate the center of gravity of thetongue, we first needed to find the edge of the tongue’ssurface in the ultrasound image and get the coordinatesof that edge. We could see the boundary of a white andblack line in ultrasound image. This black line showsthe actual tongue surface. Tracking this black line foreach rest position frame, we could get the coordinatesof the tongue’s surface at rest between sentences.

MATLAB calculations We used MATLAB andwrote code for calculating the center of gravity. Theprocess of calculating the center of gravity is as fol-lows: 1) Importing the coordinates of the tongue’s sur-face from EdgeTrak, 2) Specifying the Region Of In-terest (ROI), 3) Calculating the center of gravity of thatROI. In this research, we specified the ROI as boundedby 4 lines, the tongue’s surface, the left and rightstraight line of the ultrasound’s field of view and thelower parabola showing the surface of the ultrasoundprobe. Because of the sublingual air space (air underthe tongue tip), it is often difficult to see the tongue tipclearly with ultrasound. In specifying the ROI, we ig-nored the sublingual air space and included it as part ofthe tongue. For this reason, all center of gravity mea-surements have some error associated with them, butthis error is not systematic (i.e., it exists for all framesand should not affect the comparison results).

Correcting error for western Japanese The record-ing method that we used in this experiment had thepossibility of probe rotation from its initial position.If that were to happen, we would not be calculatingthe true center of gravity of the tongue. To tackle thisproblem, we used the following method. Each sub-ject was recorded from the side using a video camera.The reason for recording was to know the angle be-tween two blue bars: one firmly attached to the glasses(hence measuring head rotation) and the other blue barattached to wood that held the ultrasound probe (hencemeasuring probe rotation) - see Figure 1. The woodholding the probe was attached to a helmet that thesubjects wore. By knowing the angle between the blue

bars, we could calculate how much the probe rotatedrelative to the head in each rest position frame, andthen we could correct for this movement.

The process of correcting error for western Japanesewas as follows: 1) Find the rest position side-videoframe at the same time as the ultrasound tongue restposition frame. 2) Calculate central coordinates ofeach pink dot. 3) Calculate the angle between the linedefined by the upper two dots and that defined by thelower two dots. 4) Correct the error and rotate the cen-ter of gravity. For finding the central coordinates ofeach pink dot in step 2, a C language program wasused [5]. As for steps 3 and 4, we used MATLAB tomake those calculations.

Correcting error for eastern Japanese As for east-ern Japanese, we used a somewhat different method.That was because the head motion had been trackedusing a Vicon MX point-tracking system instead of avideo camera. Therefore, we used Vicon coordinatesof the glasses, chin and probe. The Vicon data had 3-D coordinates. However, we used only the y-z planebecause we were interested in rotation in the midsagit-tal plane (i.e., the same type of coordinates as the sidemovie). The process of correcting error for easternJapanese was as follows: 1) Find the coordinates froma CSV file for the markers on the glasses, chin andprobe at exactly the same time as the ultrasound restposition frame. 2) Calculate the angle between the ex-tended line of glasses and chin coordinates and the ex-tended line of two probe coordinates. 3) Correct theerror and rotate the center of gravity.

Rotating tongue’s center of gravity Based on theangle data as discussed above, we rotated the coordi-nates of the center of gravity based on the angle in thefirst rest position frame.

Calculating average and normalization Finally,we calculated the average of each subject’s center ofgravity coordinates for rest positions sorted by preced-ing vowel, i.e. あ [a], い [i], う [W], え [e], お [o].In addition, we calculated the distance between top ofprobe to center of gravity (see Figure 2). As for thisdistance, we had to normalize because each subject’sface size is not the same. In general, vocal tract size iscorrelated with face length. So, if we set the standardof face size, we can normalize easily.

The process of western Japanese normalization wasas follows: 1) Find a clear image of each subject fromthe movie. 2) Find the center point between the left

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Figure 2: Left figure is the original ultrasound image of the center of gravity in red. Right figure is the binary imageof the tongue’s center of gravity in red. The distance d is from the probe to the center of gravity of the tongue.

and right eye, and calculate the distance between thatcenter point and the chin. 3) Set the basis value equalto one, i.e., set the distance of the subject who hasthe longest face equal to one. 4) Calculate the rela-tive value from the basis value, i.e., divide other sub-ject’s distance by the distance of the subject who hasthe longest face. 5) Divide the distance between thetop of the probe and the center of gravity by that rela-tive value.

As for eastern Japanese, the method of calculat-ing the average was the same, but normalization wasslightly different from western Japanese. The only dif-ference was how to find the center point. We found thecenter point by using left side and right side glassesmarkers because we did not have video images of east-ern Japanese subjects. It was same method after step2.

3 ResultsWe show the following results: 1) the average distancebetween the tongue’s center of gravity to top of theprobe, 2) the actual coordinates of the center of gravity,3) X and Y coordinate difference between the center ofgravity and the top of the probe.

The first results can be seen in Figure 3. As forthis result, we calculated the average for eastern andwestern Japanese speakers. According to this result,the western Japanese distance is approximately 7 mmlonger than eastern Japanese.

The second results can be seen in Figure 4. This re-sult is shown by scatter plot. It shows the average loca-tion of the tongue’s center of gravity for each subject.In addition, two big points show the average of eastern

and western Japanese. Seeing the coordinate locationsof the center of gravity, the difference between easternand western is clear.

The third result can be seen in Figures 5 and 6. Fig-ure 5 focused on the X coordinates, and Figure 6 fo-cused on the Y coordinates. Looking at Figure 5, wecan see the difference of length across the vowels. Forexample, the rest position of the tongue after vowels “う [W]” and “お [o]” is farther back than the positionafter the other three vowels. As for Figure 6, however,all of the bar heights do not change so much.

4 DiscussionFirst of all, the complicated nature of this experimentalresearch caused us to greatly reflect on our methodol-ogy. We considered that the experiment needed stan-dardization of experimental methodology across allsubjects. One difficulty that we had is that the num-ber of subjects was small for both eastern and west-ern Japanese, making it difficult to generalize the re-sults to larger populations. In hindsight, we shouldhave prepared more western Japanese subjects in ex-pectation of obtaining data that could not be used. Inaddition, we should have used the same head track-ing method for eastern Japanese as was used for west-ern Japanese so that normalization of subjects wouldbe more straightforward. Furthermore, the geographi-cal area was too large for simple labels such as easternand western Japanese. It is not correct to say that alleastern and western Japanese speak one dialect respec-tively. Therefore, there may exist various articulatorysettings among eastern and western Japan respectively.By narrowing the geographical area to, for example,

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Figure 3: Distance between tongue’s center of gravityand top of probe. The right bar is eastern Japanese andthe left bar is western Japanese.

Figure 4: A plot of the coordinates of tongue’s cen-ter of gravity. Small points show each subject’s aver-age, and the two big points show eastern and westernJapanese average. The units are in pixels where 4 pix-els = 1 mm.

Figure 5: The average difference of X coordinate dis-tance between center of gravity and top of probe. Itshows all vowel average at the top, and rest positionafter each vowel below that.

Figure 6: The average difference of Y coordinate dis-tance between center of gravity and top of probe. Thegraph order is the same as Figure 5 but rotated 90◦.

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Tokyo and Osaka, we could eliminate the difference ofarticulatory setting within our groups and would focusresearch on articulatory setting of limited areas.

We can say the data collection of western Japanesewas accurate because the change of the angle of theprobe relative to the head was almost nothing and sowe did not need to rotate the images. The maximumdifference of the angle in all western data was about0.9◦, and the difference of X coordinates before andafter rotating was about 0.4 mm. Therefore, rotationcould be ignored. This result proved the data collectionsystem using the helmet and glasses accurately main-tains the probe angle relative to the head.

Another challenge we encountered when doing thisexperiment was that we needed to normalize the data,but because both normalization method were not ex-actly the same, we had a doubt about the accuracy. Butbecause eastern and western Japanese average headsize are not different, we solved that problem by cal-culating the average over all subjects. For calculatingaverage, some female data became an obstacle becausethere is a distinction of head size between male andfemale. Thus, data from two female subjects of east-ern Japanese were ignored. In addition, three westernJapanese subjects’ data were not available because ofdefects in the experiment (e.g. pilot data, difficult tosee the tongue surface in Edgetrak, etc.)

We expected that each vowel’s tongue position af-fects the rest position that follows. For example, therest position after pronouncing “う [W]” or “お [o]”would be more back as compared to other vowels be-cause those two are back vowels. As expected, voweltongue position does affect rest position as shown byFigure 5. In addition, eastern Japanese seem to be moresusceptible to the vowel tongue position because thechange of X coordinates by vowel is bigger than thatfor western Japanese. However, the Y coordinates didnot change so much, as shown by Figure 6. It meansthat rest position is more susceptible to forward andback movement.

Contrary to our expectation, the tongue’s center ofgravity for eastern Japanese did not become more for-ward than western Japanese. As shown by Figure 4,eastern Japanese average rest position tended to be lowand back. In contrast, western Japanese average restposition tended to be high and forward.

5 Conclusions and future workIn conclusion, we could find the difference of articula-tory setting for eastern and western Japanese. First, wefound western Japanese tongue’s center of gravity washigher and more forward than eastern. Furthermore,we found a relationship between the tongue’s rest posi-tion and each preceding vowel position. For both east-ern and western Japanese, rest position is susceptible tothe forward and backness of the preceding vowel posi-tion. However, it is insusceptible to the vowel height.

In future, I would like to do research comparingJapanese articulatory settings in a more limited areabased on the results of this research, and look at the ar-ticulatory setting of lips, which was beyond the scopeof this research.

AcknowledgementsFirst, I would like to express deep gratitude to Profes-sor Ian Wilson, my supervisor, for all his help. Profes-sor Yuichi Yaguchi advised about rotating the images.Naoya Horiguchi advised about my research and madethe dot tracking program. I also thank all students whoparticipated in data collection. Thanks to their help,my research was achieved.

References[1] I. Wilson, B. Gick, “Articulatory Settings of

French English Monolinguals Bilinguals”, 4thJoint Meeting of the Acoustical Society of Amer-ica and the Acoustical Society of Japan, 2006-12-01.

[2] 日本語版 wikipedia, “近畿方言 [Kinki dialect]”,http://ja.wikipedia.org/wiki/近畿方言

[3] National Language Research Institute, “日本語の母音, 子音, 音節: 長音運動の実験 音声学的研究 [Japanese vowel, consonants, syllables: Exper-imental Phonetics research of articulatory move-ments]”, Shuei Shuppan, 1990.

[4] I. Wilson, N. Horiguchi B. Gick, “Japanese artic-ulatory setting: the tongue, lips and jaw”, UltrafestIV - 2007-09-29.

[5] N. Horiguchi. “How L2 Pronunciation LearnersInterpret Articulation Instructions: An UltrasoundStudy of the Tongue”. MSc Thesis, University ofAizu, 2012.