Takeki Kamiyama

Jacqueline Vaissière

PERCEPTION AND PRODUCTION OF FRENCH CLOSE AND CLOSE-MID ROUNDED VOWELS BY JAPANESE-SPEAKING LEARNERS

Keywords: perception, production, focal vowels, French, Japanese-speaking learners !

A series of 3 experiments were conducted to examine the behaviour of Japanese-speaking learners of French (JSL) concerning the perception and production of French /u/, /y/ and /ø/, compared with English-speaking learners of French, in order to examine how L2 (second language) vowels which do not have phonemic and/or phonetic equivalents in L1 (native language) are acquired by learners.

The results indicate that JSL tend to produce French /u/ with a high F2 (> 1000 Hz), which is heard as /ø/ by native French (NF) listeners. They suggest that French /u/ is considered by JSL as phonemically similar to Japanese /u/ (as a high back vowel) and produced as such, while the phonetic realisation of French /u/ is new and different; and that /y/ is considered as both phonemically and phonetically new, and /ø/ as phonemically new but phonetically (acoustically) similar. Phonemically similar but phonetically new vowels seem to be most difficult to learn to produce accurately for foreign/second language learners.

Introduction

Learning the phonological system and its phonetic realisations in a second language is a challenge that learners face at some points of their learning process. As we all know empirically, and as many researchers have shown experimentally, some phonemes are more difficult to acquire than others. Unlike the acquisition of other components of language, such as word order of some constructions (English and German negation, for example, as summarised in [START_REF] Ellis | The Study of Second Language Acquisition[END_REF], the recent influential models of speech 1 Takeki.Kamiyama@univ-paris3.fr, jacqueline.vaissiere@univ-paris3.fr T. Kamiyama, J. Vaissière (2009). Perception and production of French close and closemid rounded vowels by Japanese-speaking learners. In Dommergues, J.-Y. (ed), Revue AILE -LIA 2, p. 9-41. a coronal context as in "tune" /tun/), but does not correspond to any vowel phoneme in these languages. Close-mid /ø/ is characterised by evenly distributed formants with no grouping, and with F2 around 1500 Hz (CALLIOPE 1989, Vaissière 2007, among others).

Note also that the open-mid /oe/ is another non-focal, "acoustically central" vowel similar to /ø/ [START_REF] Vaissière | La phonétique[END_REF], with slightly higher formants, at least in citation form. These two acoustically very similar vowels are in partially limited distribution (no /oe/ is found in word-final open syllables, and the number of minimal pairs in closed syllables is quite limited: e.g. jeûne /$øn/ and jeune /$oen/).

French /u/ (transcribed [u]) is often referred to as a "fine" example of a high back rounded vowel, and indeed, shares the same acoustic characteristics as cardinal vowel number 8 pronounced by Daniel Jones and Peter Ladefoged, i.e. grouping of the first two formants under 1 kHz [START_REF] Vaissière | Area functions and articulatory modeling as a tool for investigating the articulatory, acoustic and perceptual properties of sounds across languages[END_REF]. Japanese vowel /u/, which is phonemically high and back, usually does not correspond to phonetic realisations close to that of French /u/.

It is often described phonetically as an unrounded vowel [%]. F2 is typically located above 1 kHz (Sugito 1995, Mokhtari and[START_REF] Mokhtari | A Corpus of Japanese Vowel Formant Patterns[END_REF]. Figure 1 displays the formant values found by Sugito 1995. Note that F2 of /u/ ([%]), which is slightly higher than 1000 Hz, is higher than that of /o/([o]), and the F1 of /u/ is found between that of /i/ and that of /o/. Such values are fully explained by referring to articulation. The midsagittal profiles in [START_REF] Uemura | Nihongo no boin, shiin, onsetu: chouon undou no jikken-onseigakuteki kenkyû [Vowels, consonants and syllables in Japanese: an exprimental phonetic study on articulatory mouvements[END_REF] show that the tongue is more fronted and the lips are less rounded1 compared to a typical French [u], as illustrated in [START_REF] Bothorel | Cinéradiographie des voyelles et consonnes du français[END_REF]. Note that a weaker degree of lip rounding (as observed in Japanese) contributes to raising the first formant (F1), and that both tongue fronting and lip spreading contribute to raising the first two formants (F2) in the velar region (see the nomograms of Fant 1960 for detail).

This articulatory configuration and the resulting acoustic properties are found in [START_REF] Chiba | The Vowel: Its Nature and Structure[END_REF]Kajiyama (1955, first edition published in 1941), suggesting that it is not a recent phenomenon.

Figure 1 The first three formants (left: with phonemic transcription /u/ as the author put it) and the first two formants in two dimensions (right: the first formant -F1 -on the vertical axis, the second formant -F2 -on the horizontal axis; with phonetic transcription [%] as the author put it) of the five vowels (male voice) of Tokyo Japanese [START_REF] Sugito | Oosaka -Toukyou akusento onsei jiten CD-ROM: kaisetsuhen [CD-ROM Accent dictionary of Spoken Osaka and Tokyo Japanese[END_REF].

English /u/, on the other hand, has undergone fronting in the course of the second half of the twentieth century, as exemplified in [START_REF] Hawkins | Formant frequencies of RP monophthongs in four age groups of speakers[END_REF] for British RP (Received Pronunciation), and in [START_REF] Hillenbrand | Acoustic characteristics of American English vowels[END_REF] for American English. In Hawkins and Midgley's data, mean F2 of male speakers' /u/ ranges from 994 Hz (over 65 years old) to 1616 Hz (20-25 years old)2 . Similar figures are found in [START_REF] Deterding | The North Wind versus a Wolf: short texts for the description and measurement of English pronunciation[END_REF].

Hillenbrand et al. compared their findings with the comparable data of [START_REF] Peterson | Control methods used in a study of the vowels[END_REF], showing that the average values of the first two formants of /u/ pronounced in /hVd/ context were higher in their data both for male and female speakers.

The acoustic differences stated above among French /u/, Japanese /u/, and American English /u/ are illustrated in Figure 2 below. It can be seen that the first two formants of French /u/ are closely located together below 1000 Hz. In Japanese /u/, F2 is between 1000 and 1500 Hz, away both from F1 and F3. In American English, /u/ in the word "who" /hu/ is diphthongised, as is often the case even in isolation, with F2 lowering from above to below 1000 Hz and getting closer and closer to F1, as the intensity goes down toward the end of the vowel.

Figure 2

Wide-band spectrogram (on Praat; window length: 5 milliseconds) of French /u/ in isolation pronounced by a male French native speaker (left), of Japanese /u/ in isolation pronounced by a male native speaker of Tokyo Japanese (middle), of American English /u/ pronounced by a male speaker in the word "who" /hu/, taken from the CD-ROM of Jones et al. 2006 (right).

Indeed, the acoustic and perceptual similarity between Japanese /u/ [%] (and /uR/ [%%]: /R/ represents the second half of a long vowel in Japanese) and American English (AE) /u/ was proven by [START_REF] Nishi | Acoustic and perceptual similarity of Japanese and American English vowels[END_REF]. According to their acoustic data (4 male speakers of each language pronounced nonsense words [hVba] 3 times each in citation and sentence forms), both /u/ [%] and /uR/ [%%] in Japanese are acoustically (as far as F1 and F2 are concerned) closer to AE /u&/ than to any other AE vowel. Their perceptual assimilation experiment also showed that 12 native AE listeners assimilated both /u/ [%] and /uR/ [%%] to AE /u/ in at least 89% of the cases.

How, then, do native speakers of Japanese and English acquire the front rounded series /y/, /ø/ (and /oe/), and the high back rounded /u/ in French as a second / foreign language? [START_REF] Gottfried | Effects of consonant context on the perception of French vowels[END_REF] showed that American non-native speakers of French were significantly less accurate than native French in identifying and discriminating French vowels, especially front rounded ones. Strange et al.'s study (2004) on the perceptual assimilation patterns by American English speakers suggest that the front rounded vowels are perceived as more similar to back than front vowels. [START_REF] Levy | Perception of French vowels by American English adults with and without French language experience[END_REF] conducted an AXB discrimination experiment using the vowels /u y oe i/ pronounced by 3 native speakers of Parisian French in non-sense words /rabVp/ and /radVt/. The performances of 2 groups of 10 American English listeners (non French speakers -inexperienced -and those who had studied French extensively beginning after age 13 -experienced -) were compared. The experienced group performed better than the inexperienced on /u-oe/, /i-y/, and /y-oe/ (mean errors: Exp. 5% vs. Inexp. 24%), while they did not differ for /u-y/ (Exp. 30% vs. Inexp. 24%). It may be argued that one of the factors that could explain the even poorer discrimination of the pair /u-y/ by the experienced group (learners of French) is orthography: grapheme <u> corresponds not to phoneme /u/ but to /y/ (/u/ corresponds to the sequence <ou>).

Regarding production, [START_REF] Rochet | Perception and production of second-language speech sounds by adults[END_REF] showed that French /y/ produced by 10 Canadian English speakers in monosyllables were judged by 3 native speakers of French to be [u] or [u]-like vowel, or a vowel between [y] and [u] 92% of the time (and as an [i]-like vowel or a vowel between [y] and [i] only 8% of the time). [START_REF] Lauret | Aspects de Phonétique expérimentale contrastive : "l'accent" angloaméricain en français[END_REF] reported that native speakers of American English learning French tended to produce, in place of /y/, a sequence similar to American English /ju/, where F2 decreases gradually during the vowel. [START_REF] Flege | The production of 'new' and 'similar' phones in a foreign language: evidence for the effect of equivalence classification[END_REF] investigated the production of more advanced American learners of French and showed that their /y/ was not far from native French speakers' target, but that their /u/ had a significantly higher F2 than that of native speakers. He then suggested that it might be more difficult to pronounce a "similar" L2 phone that has a phonemic equivalent in L1 but is phonetically different (/u/), than a "new" phone which does not have any equivalent in L1 (/y/). How, then, do native speakers of Japanese learn to produce French /y/, a "new" phone, and /u/, a "similar" phone? Do they produce a native-like /y/ more easily than a nativelike /u/? How do they cope with /ø/? A series of three experiments were conducted in order to investigate that issue.

Target

French vowels /u/, /y/ and /ø/ Before investigating production and perception of Japanese learners, native speakers of French were recorded and the data compared with that of previous studies (CALLIOPE Four native speakers of French from the northern half of France (2 male and 2 female: in the 25-35 age range at the time of the recording in July 2005) pronounced 10 French oral vowels in the carrier sentence "Je dis /V/ comme dans …" (I say /V/ as in …). Each vowel was presented in phonemic transcription with an example word written orthographically (e.g. "loup" /lu/ for /u/) on a computer screen, and the speaker was invited to say the sentence. Note that all speakers were familiar with phonemic transcription of French. The vowels were presented 3 times in a random order. The recording was carried out in a soundproof room through a headset microphone, and the sound data were stored at 16 kHz/16 bits. It is indispensable to measure formants at several different time points within a vowel, firstly to check if native speakers really produce vowels with stable formants (as they are in French), and secondly to study the differences possibly observed between native and non native speakers (See [START_REF] Lauret | Aspects de Phonétique expérimentale contrastive : "l'accent" angloaméricain en français[END_REF] for American English speakers). The first 4 formants of each target vowel were measured in 5 different time zones (1. from the beginning up to the 20% point; 2. the second fifth; and so forth. See Figure 3) using Praat (Boersma and Weenink 2008), and a script written by Cédric Gendrot and modified for the present study by the first author. Unlikely values due to errors in automatic formant detection were discarded after checking the spectrogram and/or spectral slice (20 out of 2400 values, i.e. 0.8%; 12 cases for /u/ and 6 for /i/: note that /u/ is characterised by close F1/F2, /u/, close F3/F4). As expected for French, all vowel tokens had relatively stable formant values, showing that none of them were diphthongised. Table 1 indicates the mean formant values of each speaker. The vowel /ø/ pronounced by Speaker FR1 (male native French) in the carrier sentence "Je dis /ø/ comme dans leu" (I say /ø/ as in leu". Oscillogram and wide-band spectrogram (window length: 5 milliseconds) on Praat. Note also that many acoustic studies on vowels, especially on English vowels, measure only the first two formants, but that F3 value is indispensable to represent vowel systems with front-rounded vs. front-unrounded opposition. For instance, some speakers may show similar F1 and F2 values for /i/ and /y/, with only F3 differentiating the two vowels.

It is also known that F4 makes it possible to describe some cross-linguistic differences of similar phonemes: French /i/ is characterised by a grouping of F3 and F4, while English /i/ is characterised by a high F2 (higher than in French /i/, but F3 and F4 are generally not grouped: see [START_REF] Gendrot | Les voyelles /i/ et /y/ du français : focalisation et variations formantiques[END_REF]. In Japanese, the first two formants are largely sufficient to simply distinguish the 5 vowels, but it has been shown that the vocal tract during vowel production is modelled best with the fist four formants [START_REF] Mokhtari | Principal components of vocal-tract area functions and inversion of vowels by linear regression of cepstrum coefficients[END_REF]). In the present study, the first four formants are presented in tables and figures in order to better visualise the whole acoustic characteristics of vowels produced by native and non native speakers (e.g. F3 and F4 located away from the first two formants in French /u/ pronounced by native speakers vs. evenly distributed formants of the same vowel pronounced by JSL, as we shall see).

Table 1 The first 4 formants (in Hertz) of the 10 oral vowels of French pronounced by 4 native speakers of French from the northern half of France (mean of 5 measuring points x 3 repetitions). Speakers FR1 and FR2 are male, FR3 and FR4 are female speakers. Concerning vowels /u/, /y/, and /ø/ the following tendencies are found:

1) /u/, along with /o/, has very low first two formants, way below 1000 Hz both for male and female speakers, at least in citation form. These characteristics are also found in CALLIOPE. In Gendrot and Adda, F2 is above 1000 Hz; the difference probably lies in Takeki KAMIYAMA & Jacqueline VAISSIÈRE the fact that these data were collected from connected speech in radio broadcast corpora, in which vowels were generally pronounced in various (mainly anterior) consonantal and prosodic contexts. It follows that those tokens pronounced in a fronting context (e.g. between two coronals, such as in "toute" /tut/) contributed to making the mean value higher than that of /u/ in isolation. It is interesting to note that French listeners are mostly exposed to non focal realisations of /u/ in everyday speech.

2) /y/ shows close F2 and F3 between 1750 Hz and 2100 Hz for male speakers, approximately 2000 Hz and 2500 Hz for female speakers. CALLIOPE's data are quite similar to ours. In Gendrot and Adda, F2 is similar, but F3 is higher (2425 Hz for male, 2746 Hz for female speakers) than CALLIOPE's and ours. F3, which mainly depends on the front cavity in front vowels (particularly for /i/), becomes affiliated with the back cavity in hyperarticulated /y/ due to lip rounding and protrusion (for further details and references, [START_REF] Vaissière | Area functions and articulatory modeling as a tool for investigating the articulatory, acoustic and perceptual properties of sounds across languages[END_REF]: the high F3 in Gendrot and Adda's data might be due to weaker lip rounding or protrusion in many tokens in connected speech.

3) /ø/ is pronounced with no grouping of formants, with F2 around 1500 Hz (1276 and 1372 Hz for male, 1570 and 1431 for female speakers). F2 is lower than in CALLIOPE's (1417 Hz for male, 1605 Hz for female speakers) and Gendrot and Adda's data (1474 Hz and 1693 Hz for male and female speakers, respectively), but unlike /u/ and /y/, this vowel is characterised in all cases by the fact that F2 is located halfway between F1 and F3 (as is also the case with /oe/).

The values found and examined in the present section will be compared with those of Japanese learners' productions.

Preliminary study: Japanese learners' production

A first preliminary production experiment was carried out with a small group of Japanese speakers learning French (JSL) in a relatively well-controlled condition.

Method

The vowels /u/, /y/ and /ø/ were among the French vowels pronounced by the learners.

They were embedded in the same carrier sentence as the previous experiment ("Je dis /V/ comme dans …"), but the sentences were presented visually. The target vowel was represented by its phonemic transcription, and the example word, which appeared at the end of the carrier sentence, orthographically. The speakers were invited to read the sentences one by one, twice in a row.

The speakers were 3 native speakers of Japanese (2 male, 1 female). They had studied French at the University of Tokyo for one semester and volunteered for the present study.

The oral data were recorded in a soundproof booth through a headset microphone and were stored at 16 kHz/16 bits. The first 4 formants were measured using Praat, as in the previous experiment. The mean of 2 repetitions for 5 time zones during the vowel (as for native speakers' data) was calculated.

Results

The results in Figure 6 indicate that none of the 3 learners pronounced /u/ with a low F2 (< 1000 Hz), unlike native speakers. Besides, the spectrograms show that it is not a mere difference of F2 value. Figure 9.a (left and middle) illustrates a typical French /u/, in which the energy is highly concentrated around the first two formants located under 1000 Hz, and a typical token of /u/ pronounced by a Japanese learner, in which formants are distributed at similar distances, without any particular concentration of energy. This tendency is further illustrated in Figure 9.b (right), which shows energy distribution in different frequency zones.

Concerning /y/, F2 and F3 are close in the productions of Learners JSL1 and JSL2, even if F2 is higher (over 2000 Hz) than for the native speakers. By contrast, JSL3 produced a diphthong similar to the sequence /ju/ in Japanese, with F2 decreasing gradually toward the end of the vowel (see Figures 7 and8).

As for /ø/, Learners JSL1 and JSL2 produced a vowel with close F2 and F3, probably because of the English spelling <eu> /ju/ which is interpreted as Japanese /juR/, which, in turn, is associated with French /y/. JSL 3 pronounced this vowel with an F2 around 1500 Hz, making it similar to native speakers' productions. To sum up, /u/ was pronounced in a native-like manner by none of the learners, while /y/ was, to some extent (in spite of slightly high F2), at least by two out of the three learners.

/ø/ was produced in a native-like manner by one of them. Are these tendencies observed with a larger number of learners? Is there some more variability? How do they perceive these vowels? Are the tendencies observed in production explained by the learners' perceptual difficulties? A series of 3 experiments were conducted to tackle those issues:

AXB discrimination test including pairs /u-y/, /y-ø/, /u-ø/ with 14 JSL; production of /u y ø/ by 47 JSL; evaluation of JSL's /u y ø/ by 16 native French listeners.

Experiment 1: JSL's perception (AXB discrimination)

Experiment 1 consisted of an AXB discrimination task in which 14 Japanese-speaking learners listened to triplets composed of pairs including /u-y/, /y-ø/, and /u-ø/. The aim was to clarify the perceptual difficulties that JSL face and relate the discrimination results to those of production tasks.

Method

Seventy-two triplets of vowels presented in isolation were composed of six pairs of vowels /u-y/, /y-ø/, /u-ø/, as well as /i-e/, /u-o/ and /(-a/: 6 pairs x 4 combinations and orders of tokens x 3 speaker conditions: 1) all 3 stimuli in the triplet were pronounced by the same speaker (female FR3); 2) the second one was pronounced by another speaker of the same sex (female FR4); 3) the second was pronounced by another speaker of the opposite sex (male FR1). The vowel contrasts /i-e/ and /o-u/ were included since some cases of incorrect identification were observed in [START_REF] Kamiyama | La production et la perception des voyelles orales françaises par les apprenants japonophones : une étude pré! liminaire[END_REF]. On the other hand, it is predicted from the results of the same study that /(-a/ will be discriminated almost perfectly. The mean duration of the vowel tokens was 180 milliseconds (ms). The intrastimulus interval (between the stimuli in each triplet) was set to 1 second, so that the stimuli would be processed as linguistic (phonemic) units rather than physical (acoustic) ones; the goal of the acquisition of L2 sound system is to establish phonemic categories of L2, not to develop the ability of discriminating any pairs of sounds based on their acoustic differences. The inter-stimulus interval (between triplets) was set to 5 seconds.

The whole experience lasted 19 minutes.

The subjects were 14 high school students studying French (as a second foreign language) at Musashi High School (Tokyo, Japan). Half of them had studied it for 15 months ("level 1"), the other half for 27 months or more ("level 2"). They listened to 2 repetitions of the triplets (144 trials). They were asked to choose either the first or the third sound in each triplet as identical to the second one, and gave their answers on a sheet of paper. They were seated in a classroom, and heard the stimuli through a pair of loudspeakers installed in the room. It should be noted that in the usual classroom situation learners listen to L2 sound material either directly from the instructor or through loudspeakers, except in language laboratories, where each workstation is equipped with a headset.

Results

The results of the experiment are shown in Figure 10. The mean score of all 14 JSL (the two levels included) was better for /u/-/y/ (94.9%) than for /y/-/ø/ (91.1%), and /u/-/ø/ (84.8% correct) was the most difficult of the three pairs. When we look at the difference between the two groups of learners, it is almost inexistent for /u-y/, but larger for /u-ø/, and still larger for /y-ø/ although statistically non significant. These results suggest that the distinction between /u-y/ is the least difficult to acquire, that /u-ø/ is the most difficult, and that there is an effect of learning for /y-ø/.

We can also observe that /( -a/ was discriminated almost perfectly. As for /o-u/, the score was as low as that of /u-ø/ for both learner groups, while the advanced group obtained better score (as high as /u-y/) than the other group (as low as /u-ø/) for the pair /i-e/ (see [START_REF] Kamiyama | Apprentissage phonétique des voyelles orales du français langue étrangère chez des apprenants japonophones[END_REF] for further details on these pairs). How, then, are these perception results related to the production of these vowels?

Experiment 2: JSL's production

Experiment 2 consisted of an acoustic analysis of the 3 French vowels /u/, /y/, and /ø/ pronounced by 50 JSL studying French in 4 different classes. The aim of this experiment was to confirm the tendencies observed in our preliminary study, and to compare the results with the previous perception experiment.

Method

French oral and nasal vowels including /u/, /y/, and /ø/ were embedded in the carrier sentence "Je dis /V/ comme dans …" as in the preliminary study. The sentences were arranged in a random order. They were presented in the same experimental session and the subjects were invited to read the sentences one by one. At the end of the list of sentences, a dummy sentence was inserted so that all the other sentences would be read with a similar rhythm and intonation.

The 50 subjects were groups of students attending 4 different classes in French as a foreign language in universities of the Tokyo area. Group 1 (elementary) was mainly composed of learners who had learned French for one semester (3 hours a week), Group 2 (intermediate) of those who had studied it for 2 years (9 to 12 hours a week), Group 3 (intermediate) of those who had studied it for 1 to 1.5 years (9 hours a week), and Group 4 (upper intermediate) of those who had studied it for one semester (7.5 hours a week) at the university, with some prior learning experience (e.g. 2 to 8 hours a week for three years in high school).

The recording was carried out in a CALL (computer assisted language learning) laboratory. The subjects read the sentences at their own pace, using a headset microphone, and the sound was stored on the network at 22.5 kHz/16bits. They were asked to repeat the list 5 times. Some repeated it 6 times, others less than 5 times. The data of those who did not follow the instructions (e.g. those who did not pronounce the target vowel) were discarded. The data of 47 learners (out of 50; 40 female and 7 male) were thus retained.

The first 4 formants of /u/, /y/, and /ø/ were measured near the beginning, in the middle, and near the end of the vowel. The mean values throughout the vowel were also measured and compared with the mean of the three values measured at three points. Some parts of the vowels were excluded for reasons of recording quality or transitions from the preceding word in the carrier sentence. In order to determine quantitatively if the vowel is diphthongised (in particular, /y/ pronounced like Japanese /ju/), F2 was compared at the beginning and at the end of the vowel ("F2 change": F2 at the end divided by F2 at the beginning).

The two measures (1. mean of all values measured every 6 milliseconds during the whole vowel, and 2. mean of the three measures; toward the beginning, middle and end) were compared, and the error was calculated for each formant and each speaker by dividing the difference between the two measures by the mean of the three-point measure. The maximum error between them was 6.8% (0.7% in average). In 78% of the cases, the error was smaller than 1%. Assuming that such error is negligible, the mean of the whole vowel was used as the formant value.

Results

Figures 10-12 show the mean first 4 formants of the three vowels /u y ø/ pronounced by (FR3 and FR4). The data of the 7 male learners were not included in the calculation of the mean, since the formant values are known to be different for male and female speakers except those due to Helmholtz resonance such as F1 of French /i y u/, F2 of French /u/ [START_REF] Fant | Acoustic Theory of Speech Production: With Calculations based on X-Ray Studies of Russian Articulations[END_REF]. In spite of the large intra-and inter-speaker variability observed in the data By contrast, as many as 20 students our of 47, including elementary level learners (Group 1), succeeded in pronouncing a /y/ token with close F2 and F3 (with F2 not higher than 2400 Hz) without diphthongisation in at least one of the repetitions, even though their production is highly variable except for upper-intermediate learners (Group 4). The mean formant values of the 40 female learners show that the difference between the learners and the native speakers is smaller than that of /u/. Group 4 presents closer F2/F3 than the other JSL groups, making them similar to the native speakers' values in spite of higher F2/F3, probably due to insufficient lip protrusion compared to French native speakers (Figure 12). These findings suggest that JSL learn to produce /ø/ in a native like manner more easily than /y/, which in turn is easier than /u/.

How, then, are these vowels actually perceived by native speakers of French?

Experiment 3: native speakers' perception of vowels /u y ø/ produced by JSL

Experiment 3 consisted of a test of identification and rating of JSL's /u y ø/ by native listeners of French. The aim of this experiment was to examine how the acoustic properties of these vowel phonemes produced by JSL and observed in the previous experiment are perceived by native speakers of French.

Method

First, 6 tokens of /u/ in isolation pronounced by the 3 JSL (2 male, 1 female) in the preliminary study were chosen. Then, 10 tokens of the same vowel produced by the same 3 JSL in a task of immediate repetition [START_REF] Kamiyama | La production et la perception des voyelles orales françaises par les apprenants japonophones : une étude pré! liminaire[END_REF] were added. Finally, 2 tokens of /u/ pronounced by 2 (1 male, 1 female) of the 4 JSL who produced it with low first two formants (< 1000 Hz) in Experiment 2 were added so that the F2 of the stimuli would vary in a balanced manner. A total of 18 tokens of /u/ were thus selected (Figure 14, top left). As for /y/ and /ø/, the tokens produced in the same series of experiments as each one of /u/ were selected. (Figure 14). The mean duration of the stimuli was 225 ms.

Sixteen native speakers of French (NF) aged between 23 and 34 listened to these 54 stimuli (3 vowels x 18 tokens) 4 times, choosing one of the French vowels they had heard and giving a rating corresponding to its goodness (1 to 5). They were seated in a quite, closed room with a computer. The stimuli were presented through a headphone, and the listeners used a mouse to choose their answers on a computer screen. The interface used for the experiment was ExperimentMFC 4 on Praat [START_REF] Boersma | Praat: doing phonetics by computer (Version 4.6.13)[END_REF]. There was no time limit for the answers: the listeners responded at their own pace. The whole experiment took approximately 20 to 25 minutes.

Each stimulus was thus identified and rated 64 times (4 repetitions x 16 NF listeners).

The number of times each stimulus was identified as a given vowel was calculated along with the mean goodness score ranging from 0 (no response for that category) to 5 (given the whole vowel stimulus (thus 18 columns for each vowel, 11 for male learners', 7 for female learners' stimuli). The stimuli are arranged here in the order of their F2 value for /u/ and /ø/, of F3 for /y/. Note that the tokens of /y/ pronounced by the female learner in the preliminary study were mostly diphthongised, as in Japanese /ju/.

Results

The results are shown in Figures 161718. The findings include the following: i) /u/ (Figure 15): the stimuli with an F2 below 1000 Hz were almost unanimously identified as /u/ with a good rating score. Those with an F2 between 1000 and 1100 Hz were categorised as /ø/ almost as often as /u/. With an F2 above 1100 Hz, the stimuli were mainly identified as /ø/ with a good rating score. F2 shows a very good correlation (0.89 for the stimuli of male learners, 0.83 for those of female learners) with the index "/u/ score -/ø/ score" (ranging from -5 to 5: see Figure 16). ii) /y/ (Figure 17): the stimuli with close F2/F3, and with a not too high F2, were mainly perceived as /y/ with a good rating score. Those with diphthongisation, as in Japanese /ju/

[j%] (produced by the female learner examined in the preliminary study: see Figure 14) iii) /ø/ (Figure 18): the stimuli with F2 around 1500 Hz and not close to F3 were identified mainly as /ø/ and obtained good rating scores.

Discussion and conclusion

The present series of experiments has shown and confirmed the following points:

1. JSL have difficulty distinguishing /u-ø/ perceptually, less so for /y-ø/, and still less for /u-y/ (Experiment 1).

2. Out of the 47 JSL examined, only 4 produced a native-like /u/, whereas 20 produced a more or less native-like /y/ at least once, and 31 JSL did so for /ø/ (Experiment 2).

3. NF listeners mainly perceived /ø/ when they heard stimuli intended as /u/ by JSL (but produced with a high F2 between 1100 and 1600 Hz), giving a mean rating of 2 to 4.5 out of 5 for /ø/, but less than 1 for /u/ (Experiment 3).

Production

The findings in 2 above confirm the tendency observed in the preliminary study conducted with a smaller number of learners, suggesting that it is not only those three individuals but a larger number of JSL who had difficulty producing /u/, less so with /y/, and still less with /ø/.

It should also be noted that the 4 learners who pronounced a native-like /u/ in Experiment 2 all had a considerably richer learning experience: three of them had lived in a French speaking country, and the other had learned French in a language school for 3 years (2 hours a week).

The phonetic differences between French /u/ and Japanese /u/ (or between French /u/ and English /u/) are usually known, at least explicitly, only to phoneticians and linguists as well as a small number of students who study phonetics. Most non-native teachers and learners tend to consider French and Japanese /u/ as practically the same sounds and do not pay particular attention to their articulatory and acoustic differences. On the other hand, /y/ is considered to be a "new" vowel that does not exist in L1 from the beginning, and so relatively much attention is paid to the difficulty of its perception and production.

It is also easier to show the articulatory configuration of /y/ than that of /u/. Lip rounding and protrusion, which are shared characteristics of /u/ and /y/, are relatively easy to show and perceive visually. However, it is much more difficult for learners to perceive the tongue position of /u/, which is further back compared to Japanese /u/, and to articulate it correctly, simply because it is invisible from outside. It is not easy for them to associate mid-sagittal profiles and position of their own tongue either. This is why researchers and practitioners have devised such methods as moving from low back vowels to high back

[u], or using the help of pitch (association of low pitch and [u]).

It is interesting to note that in French both /u/ and /y/ are "quantal" vowels in which two formants are found close together and enhance the amplitude of each other, making them perceptually salient. However, when they are perceived and produced as L2 phones, learners behave differently due to the L1 vowel system.

Another category should be taken into account for the case of /ø/ learned by JSL, who had less difficulty acquiring it. We saw earlier that French /ø/ is characterised by equally distributed formants, and these characteristics are also observed in Japanese /u/. In Experiment 3 the tokens of French /u/ pronounced by JSL, which may be considered to be close to Japanese /u/, were mainly perceived as /ø/ by NF listeners. This finding also supports the acoustic similarity of French /ø/ and Japanese /u/, even if they differ in terms of articulation (front rounded French /ø/ vs. not fully back, not fully rounded Japanese /u/). The difficulty probably lies in the fact that French /ø/ is considered (taught) to be an new sound to JSL, transcribed with an unfamiliar symbol, which might lead to some confusion, due also to the spelling (association of <eu> with English /ju/, leading JSL to pronounce a sequence like Japanese /ju/ or French /y/, as we observed in the preliminary study on production). The case of /u/ is totally different; on the one hand, it is transcribed with a familiar symbol (letter u is used to represent Japanese phoneme /u/ in roman transcription rômaji, as in "Ueno" /ueno/: a place name in Tokyo). On the other hand, the large phonetic difference between the target sound (French /u/) and the L1 sound (Japanese /u/) is not consciously noticed by most JSL. This lack of consciousness might make its acquisition harder than that of /y/, which is phonetically "new", but also phonemically in the sense that there is no equivalent phoneme in the L1 (Japanese) vowel inventory; a fact that might help learners to notice the deviation from the target form more easily. We suggest a hierarchy of difficulty in production represented in Table 2: L2 phonemes could be considered as phonemically or phonetically, similar or new, as compared to L1 phonemes.

Table 2 Difficulty of acquisition of production; in terms of phonemic and phonetic similarity.

Perception

Another interesting issue is the relative perceptual difficulty of pairs /u-ø/ and /u-y/ by JSL and native speakers of American English learning French (AESL), as reported in [START_REF] Gottfried | Effects of consonant context on the perception of French vowels[END_REF], [START_REF] Levy | Perception of French vowels by American English adults with and without French language experience[END_REF], and mentioned in the introduction of the present paper. Experiment 1 resulted in the following hierarchy of difficulty: /u-ø/ > /y-ø/

Figure 3

 3 Figure 3 Illustration of the 5 time zones in which formant frequencies were measured.

Figure 4

 4 Figure 4 Graphic representation of the formant values of native French speakers FR2 (male: top) and FR3 (female: bottom) in Table 1. The first 4 formants (right), and the first 3 formants represented in a vowel triangle (right). Note the grouping of F3 and F4 for /i/ for both speakers. Note also that FR2's /i/ and /e/ have similar F1 and F2 values, but are distinguished by F3 and F4.

Figure 5

 5 Figure 5 The first 4 formants (in Hertz) of the 10 oral vowels of French pronounced in [pV] and [pV'] by 10 male (left) and 9 female (right) native speakers of French. Two repetitions per subject (CALLIOPE 1989: 84).

Takeki

Figure 6

 6 Figure 6 The first 4 formants (left) and the first 3 formants (in a 3D vowel triangle: right) of the ten oral vowels of French pronounced by 3 Japanese-speaking learners (JSL), Learners JSL1, JSL2 (male: top and middle) and JSL3 (female: bottom). Mean of 5 measures x 2 repetitions.

Figure 7 A

 7 Figure 7 A 3D representation of the first 3 formants (Hz) of the vowels pronounced by Learner JSL3 (5 measuring points during the vowel x one of the 2 repetitions).

Figure 8

 8 Figure 8 The formants values (left) and the spectrogram of one of the two repetitions of /y/ pronounced by Learner JSL3 (female).

Figure 9 .a

 9 Figure 9.a The spectrograms of /u/ pronounced by the native speaker FR1 (left), and by the Japanese-speaking learner JSL1 (middle).

Figure 9 .

 9 Figure 9.b relative intensity in 3 frequency zones (0-1 kHz, 1-2 kHz, 2-3 kHz) of /u/ pronounced by the 4 native speakers (fr: mean of 12 tokens) and by the 3 Japanese-

Figure 10

 10 Figure 10 The results of the AXB discrimination task. Perception of French vowels by Japanese high school students. Mean score of each of the two groups (7 listeners in "level 1" and 7 in "level 2" groups), 2 repetitions of 72 triplets. Error bars represent 1 standard error.

  (e.g. a given learner produced a [y]-like vowel 3 times and [j%]-like vowel 2 times for target phoneme /y/), the mean values of each group reveal some relevant tendencies.Concerning /u/, only 4 learners out of 47 (40 female and 7 male) produced a low F2 below 1000 Hz. All other speakers produced an F2 higher than 1000 Hz. The mean first 4 formants of female learners (Figure11) show that none of the 4 groups present values similar to those of the 2 female native speakers.

Figure 11

 11 Figure 11 The mean first 4 formants of /u/ pronounced by 40 female JSL studying French in 4 different groups: Group 1 (elementary: 14 female learners, 70 repetitions), Group 2 (intermediate: 7 female learners, 34 repetitions), Group 3 (intermediate: 12 female learners, 63 repetitions), Group 4 (upper-intermediate: 7 female learners, 34 repetitions). The mean of the two female native speakers of French (FR3 and FR4, 6 repetitions) were added on the right-most column for comparison. The error bars represent the standard deviation.

Figure 12

 12 Figure 12 The mean first 4 formants of /y/ pronounced by 40 female JSL studying French in 4 different groups: Group 1 (elementary: 14 female learners, 69 repetitions), Group 2 (intermediate: 7 female learners, 34 repetitions), Group 3 (intermediate: 12 female learners, 63 repetitions), Group 4 (upper-intermediate: 7 female learners, 34 repetitions). The mean of the two female native speakers of French (Fr3 and FR4, 6 repetitions) were added on the right-most column for comparison. The error bars represent the standard deviation.

Figure 13

 13 Figure 13 The mean first 4 formants of /ø/ pronounced by 40 female JSL studying French in 4 different groups: Group 1 (elementary: 14 female learners, 68 repetitions), Group 2 (intermediate: 7 female learners, 34 repetitions), Group 3 (intermediate: 12 female learners, 63 repetitions), Group 4 (upper-intermediate: 7 female learners, 34 repetitions). The mean of the two female native speakers of French (Fr3 and FR4, 6 repetitions) were added on the right-most column for comparison. The error bars represent the standard deviation.

Figure 14

 14 Figure 14The first 4 formants of the stimuli used in the experiment (18 tokens of each of the three vowels /u y ø/ pronounced by 3 male and 2 female JSL). Each column represents the mean first 4 formants of all values measured every 6 milliseconds during

Figure 15 Figure 16

 1516 Figure 15 Results of the identification task (above: 64 responses) and mean rating (below: 0 to 5). Eighteen tokens of /u/ pronounced by 5 JSL (3 male and 2 female learners), 64 responses (4 repetitions x 16 NF listeners) for each stimulus.

Figure 17

 17 Figure 17 Results of the identification task (above: 64 responses) and mean rating (below: 0 to 5). Eighteen tokens of /y/ pronounced by 5 JSL (3 male and 2 female learners), 64 responses (4 repetitions x 16 NF listeners) for each stimulus.

Figure 18

 18 Figure 18 Results of the identification task (above: 64 responses) and mean rating (below: 0 to 5). Eighteen tokens of /ø/ pronounced by 5 JSL (3 male and 2 female learners), 64 responses (4 repetitions x 16 NF listeners) for each stimulus.

  identified either mainly as /ø/, or equally as /u/, /y/, or /ø/, but the rating score was low in all cases.

	Takeki KAMIYAMA & Jacqueline VAISSIÈRE
	Aile … Lia 2 -2009	32

were

  RésuméDeux expériences de perception et une expériencede production ont été effectuées afin d'examiner les comportements des apprenants japonophones (AJ) concernant les trois voyelles /u/, /y/ et /ø/, et de les comparer avec le cas des apprenants anglophones. Les résultats de ces expériences suggèrent les points suivants : i) les AJ ont tendance à produire le /u/ français avec un F2 élevé (> 1000 Hz), ce qui est perçu comme /ø/ par les auditeurs natifs francophones (NF) ; ii) pour les AJ, le /u/ français pourrait être considéré comme similaire sur le plan phonémique (en tant que voyelle postérieure fermée) mais nouveau sur le plan phonétique, /y/ comme nouveau sur les plans phonémique et phonétique, /ø/ comme nouveau sur le plan phonémique mais similaire sur le plan phonétique (acoustique). Les voyelles phonémiquement similaires mais phonétiquement nouvelles semblent les plus difficiles à apprendre à produire correctement pour les apprenants des langues étrangères/secondes.

	!

The X-ray movie "Cineradiograph of Japanese Pronunciation" produced by the Speech Laboratory of the National Institute for Japanese Language is available (in Japanese) on the website of the Institute: http://www6.kokken.go.jp/x-sen/

The eleven monophthongs in RP were spoken in /hVd/ contexts by five men in each of the following age groups: 20-25,

35-40, 50-55, and 65-73 years in 2001. The test words in citation form were read four times in a randomised list.

Acknowledgments:

The authors wish to express their gratitude to Miho Inoue for kindly accepting to record her students during precious class time, and to the two anonymous reviewers for reading an earlier draft of the paper and for providing valuable comments.

> /u-y/, whereas it is with the pair /u-y/ that experienced AESL were found to have difficulty, according to [START_REF] Levy | Perception of French vowels by American English adults with and without French language experience[END_REF].

The fact that the pair /u-y/ is not so difficult as /u-ø/ for JSL could be explained by the existence of the sequence /ju/ in Japanese. In our preliminary study on JSL's production, we observed cases in which French /y/ was pronounced as a sequence resembling Japanese /ju/. In loanwords from French, for instance, /y/ is usually interpreted as /ju/, while /u/ is interpreted as /u/ (e.g. "Lumière" /lymj('/ > /rjumieRru/, "Louvre" /luv'/ > /ruRburu/: /R/ represents the second half of a long vowel. For more data and detailed phonological analysis on loanword adaptation in Japanese from French and English, see [START_REF] Shinohara | Analyse phonologique de l'adaptation japonaise de mots étrangers[END_REF]. Note that /u/ and /ju/ are in opposition in Japanese (ex. /uku/ "to float" vs. /juku/ "to go"; /'umi/ "sea" vs. /'jumi/ (female first name)). In terms of PAM, the French pair /u-y/ could thus be considered as "two-category assimilation", in which case discrimination is expected to be excellent.

Sequences /u/ and /ju/ are also found in English, but the opposition could be considered as partially neutralised because of "j-dropping", even more so in American English (see [START_REF] Wells | Longman Pronunciation Dictionary[END_REF], for example). There exist some minimal pair words in contexts that did not undergo the phenomenon (e.g. "cue" /kju/ vs. "coo" /ku/), but the two sequences are neutralised in other contexts (e.g. "tune" /tun/, "toon" /tun/). It is not easy to decide whether j-dropping was caused by the similarity between /u/ and /ju/, or j-dropping favoured the similarity between these two sequences. In any case, it is likely that AESL cannot easily assimilate French /u-y/ to English /u-ju/, unlike JSL (note also that English /u/ is diphthongised, with its F2 lowering during the vowel, unlike Japanese /u/). This case could thus be considered as an example of "single-category assimilation" (or "category-goodness difference") rather than "two-category assimilation" in terms of PAM, making it difficult for native speakers of American English to distinguish this pair.

One of the reasons of the relative ease with which JSL learn to distinguish French /u/ and /y/ perceptually may be due to the fact that both /u/ and /y/ have the advantage of being focal vowels (with a high concentration of energy). Besides, the focal nature of these vowel phonemes may and should be included in their symbolic representation to better characterise them [START_REF] Vaissière | La phonétique[END_REF]. In addition, /u/ has a much lower centre of gravity PERCEPTION AND PRODUCTION OF FRENCH CLOSE AND CLOSE-MID ROUNDED VOWELS BY JAPANESE-SPEAKING LEARNERS 37 than /y/ in all cases, which may explain in part why /u/-/y/ is easier to discriminate than the other pairs.

The present article only dealt with vowels in isolation. [START_REF] Levy | Perception of French vowels by American English adults with and without French language experience[END_REF] report the effect of consonantal context (bilabial and alveolar contexts) on American English speaking learners (AESL)'s perception of French vowel pairs including /u/, /y/ and /oe/. It will be interesting to examine how the consonantal context influences the perception of the three vowels /u y ø/ by JSL.

Also, the findings of the present study could be applied to the development of a training system of these three vowels, and eventually, of others: users-learners would be able to pronounce the target vowel and get feedback on the acceptability as a token of the intended vowel, based on the correspondence between the real-time acoustic analysis of the vowel produced, and the expected values by native listeners. Learners are thus led to associate the mental representation of the target vowel and the articulatory gestures needed for its phonetic realisation. Further experiments collecting more detailed and ample data will be needed to specify the parameters required for such a system.


Kamiyama Takeki
email: takekik@phiz.c.u-tokyo.ac.jp

Perception of Foreign Accentedness in L2 Prosody and Segments: L1 Japanese Speakers Learning L2 French

In order to examine the production of Japanese-speaking L2 learners of French, a series of perception tests were conducted with 17 native speakers of French (from mainland France). The subjects listened to French short phrases 1) synthesized with Mbrola using (European standard and Canadian) French and Japanese segments, combined with duration and F0 found in the recording of phrases read by Japanese learners and French native speakers, 2) read by Japanese learners and French native speakers, and then re-synthesized with manipulation of local duration and F0. The results indicate that duration and F0 play an important role in the perception of foreign accent.

Introduction

The role played by the suprasegmental features in the intelligibility and the naturalness of L2 learners' production has long been underestimated in the practice of language teaching. Recently, however, we have come to attach more importance to it (Dalton and Seidelhofer [START_REF] Dalton | Pronunciation[END_REF]) and have seen some works that demonstrate the relative importance of suprasegmental features in L2 learners' speech (Suzuki [START_REF] Suzuki | Gengo gijutsu to shite no purosodii (Prosody as a Linguistic Skill)[END_REF] for F0, duration and intensity, Tajima et al. [START_REF] Tajima | Effects of temporal correction on intelligibility of foreign-accented English[END_REF] for duration). This paper deals with the production of Japanese-speaking L2 learners of French.

Japanese is usually classified as a pitch-accent language. The words, except for some particles, are either accented or unaccented at lexical level. If it is accented, the lexical accent is realized as a fall in F0 anchored to a specified mora in the word (Kubozono [4], among others). There is generally an F0 jump between the first two morae in the word. Intonation does not change much the underlying F0 pattern of the word: the accented words preserve the fall in F0, and there is usually no continuation rise (which is dominant in French; realized but less extensively in English).

Japanese is also classified as a mora-timed language from the rhythmic point of view. Although the acoustic reality of the isochrony of morae in its strict sense is denied (Beckman [START_REF] Beckman | Segment Duration and the 'Mora' in Japanese[END_REF]), there are claims that some compensation mechanism is at work at the mora level (Kurematsu [6], Sagisaka [START_REF] Sagisaka | Nihongo on-in no jikanchou seigyo to chikaku (Duration control and perception of phonemes in Japanese)[END_REF]). At least, native speakers tend to segment, when they are asked to, at mora level, and it is the number of morae that count in poetry.

The target language French is considered as an intonation language, and there is no pitch pattern associated to words at lexical level. When embedded in a sentence, a word may be found with a rising, neutral or falling F0 contour, depending on its position in the sentence (the first word tends to be rising, the penultimate word rising, and the last one falling) and on its relation with the next word (the more independent, the higher the rising is). There is a rise at the end of each group, a major rise at a major node, and a minor one at a minor node (Vaissière [8], for example). This feature gives the language an acoustic impression of rising intonation, which contrasts with Japanese. The rising tendency in French and the falling one in Japanese are also observed in infants' productions (two-syllable utterances of 18-month-old children: Hallé et al. [START_REF] Hallé | Beginnings of prosodic organization: Intonation and duration patterns of disyllables produced by Japanese and French infants[END_REF]).

As far as rhythm is concerned, French falls into the "syllable-timing" category. Here again, the acoustic reality of syllable isochronicity is not found (Wenk and Wioland [START_REF] Wenk | Is French really syllabletimed?[END_REF]), and final lengthening disrupts syllable isochronicity. Syllable is the basic unit in poetry and it gives at least an isochronous acoustic impression. It is syllable (and not mora) that corresponds to a strong cognitive reality in French.

There exists an important difference in duration between the two languages, namely, sentence-final lengthening. Final lengthening is a widely observed phenomenon. In French the last syllable in rhythmic groups (or phrase) is lengthened and generally a (major or minor) continuation rise is superimposed on it. Lengthened duration and F0 peak (minor phrase) or F0 rise (major rise) leads to the perception of "accent de groupe" (Delattre [START_REF] Delattre | Accent de mot et accent de groupe[END_REF]). In Japanese, a slight phrase-final lengthening is observed, but there is no sentencefinal lengthening (Takeda et al. [START_REF] Takeda | On sentence-level factors governing segmental duration in Japanese[END_REF]). The difference in the importance of final lengthening thus observed in adults' speech in the two languages is also present in infants' speech, just as the case of pitch (disyllabic utterances of 18-month-old French and Japanese: Hallé et al. [START_REF] Hallé | Beginnings of prosodic organization: Intonation and duration patterns of disyllables produced by Japanese and French infants[END_REF]).

Therefore, when considering L1 speakers of Japanese learning L2 French, it can be expected that the learners do not fully reproduce 1) the rising tendency in pitch at the end of internal phrases, more precisely, continuation rises, and 2) phrase-and sentence-final lengthening. These characteristics are indeed observed in some learners' short read utterances (Kamiyama [13]).

The present study deals with the French native speakers' perception of French produced by Japanese learners. In order to approach the issue, we conducted a series of perception tests using stimuli synthesized 1) with the diphone synthesizer Mbrola [START_REF] Dutoit | Mbrola Project[END_REF], modifying the quality of the segments (into European Standard French, Canadian French and Japanese phonemes) while keeping the prosody intact, and 2) with Praat [START_REF] Boersma | Praat[END_REF] (PSOLA algorithm) for F0 and duration manipulations of original sentences, while keeping the segments intact.

Methodology

Stimuli

8 short phrases in French (Table 1) were read by 11 L1 Japanese speakers learning L2 French and by 4 native speakers of French. The learners' were second-year university students who had learned French for one academic year at a university in Japan. For each test 5 recordings were selected from those learners with non-native-like prosody, as well as the corresponding 5 phrases read by a native speaker.

Un peu de panaché. Beaucoup de panaché. L'économie des États-Unis. L'économie du Canada. Les mots à éviter. Une compagnie dénationalisée. Une photo de chameaux. Il y a une photo de chameaux.

Table 1: Phrases used in the tests.

Test 1:

The duration of each phoneme was measured, and fundamental frequency (F0) was detected at 10 ms time steps.

We then used Mbrola to create 6 types of stimuli combining two factors: 1) segments in French (fr), French Canadian (ca), Japanese (jp); 2) prosody (phoneme duration and F0) of Japanese learners' productions (Pros JP) and that of French native speakers' (Pros FR). (cf. Test 2: Praat was used to manipulate final lengthening and continuation rise of 5 phrases: they were 1) added to the utterances of the learners that lacked them, 2) removed from those of French native speakers. Speech rate and pause: Learners tended to pronounce at a slower pace, and with frequent pauses. In order to test if these two factors alone influence the listeners' judgement, we also selected one phrase and created a set of stimuli by 1) slowing down the whole phrase, 2) inserting a pause, 3) doing 1) + 2

Subjects

17 native speakers of French (from mainland France) participated in the tests.

Experimental protocol

The subjects were asked to answer the following question: "Est-ce qu'il/elle a bien dit ?" (Did he/she say well?). They were provided with a 7-degree scale, ranging from 1 (pas du tout -not at all) to 7 (très bien -very well), and were asked to click on the area on a computer screen corresponding to their answer.

Each test (Tests 1 and 2) was preceded by a training session, and was divided into two sub-parts with a break between them. In order to control the side effect due to the presentation order, the two tests as well as the stimuli were presented in a different order to half of the subjects. Also, each stimulus type was presented twice to check the consistency of judgment.

Results

Test 1 (Mbrola)

Intra-speaker response consistency

The two responses for the 60 stimuli show a high correlation with every subject (Spearman's rank order correlation: ρ = 0.61 (median of all subjects), p < 0.05). Given that the listeners are consistent in their responses, we take the mean of the two scores.

Presentation order

Order of the tests (Test 1 and Test 2): A high correlation (Spearman's ρ = 0.93, p < 0.05) is found between the mean scores of the two groups of subjects. The difference in mean score (for all the stimuli) of the two groups is NOT significant (Student's one sample t test: t15 = 0.57, p > 0.05).

Order of stimuli:

A high correlation (ρ = 0.68, p < 0.05) is observed between the two groups. Also, the difference in mean score (of all the stimuli) of the groups is NOT significant (t15 = 0.23, p < 0.05).

Factor PROSODY

The mean score for Pros FR (Prosody of the French speakers) is 4.3, and that for Pros JP is 3.2 (Figure 1). The difference is statistically significant (Student's paired t test: t29 = 9.25, p < 0.05). If we look at each listener, 16 subjects out of 17 show a significant difference. When we consider only those stimuli with Segments jp (Seg jp), the difference in mean score (FR 3.5, JP 2.7) is also significant (t9 = 2.94, p < 0.05. Figure 2), and 11 out of 17 subjects show a significant difference.

Factor SEGMENTS

The mean scores for Seg fr, ca and jp are 4.5, 3.6, and 3.1 respectively. A global effect of Segments on the score is found (ANOVA: F(2, 57) = 15.84, p < 0.05), the difference between each one of the categories (ca, fr, jp) contributing the global effect (Figure 3). Out of the 17 listeners, 14 show a global effect of Segments. A posteriori comparison between two categories (Student's paired t test) reveals an individual difference of the subjects in the hierarchy of the three conditions. For example, about half the subjects judged Segments fr significantly better than the other two ( JP+Seg fr (10 stimuli each).

Pros and Segments

Let us compare now the two factors. What interests us here the most is the comparison between the following two conditions: 1) Pros FR + Seg jp and 2) Pros JP + Seg fr (Figure 4). The mean scores are 3.5 and 3.7 respectively. The difference is not significant (t9 = 0.83, p > 0.05). Out of the 17 listeners, 9 judged Pros JP + Seg fr better (the difference being significant for 3 of them), and the others judged the other combination better (none of them shows a significant difference). Also, the results of ANOVA (on the mean) with these two factors indicate that both of them (Prosody: F(1, 36) = 42.93, p < 0.05; Segments: F(1, 36) = 59.67, p < 0.05) as well as the interaction between the two (F(1, 36) = 4.91, p < 0.05) are significant. (Figure 5) As for each listener, factor Prosody is significant for 16 listeners, Segments for 15, and the interaction for 8 subjects.

Intensity adjustment

• Pros FR: The mean scores with and without adjustment are 4.2 and 4.4 respectively. The global difference is significant (t14 = 2.31, p < 0.05. Figure 6). However, only 2 subjects show a significant difference. • Pros JP: The mean scores with and without adjustment are 3.0 and 3.4 respectively. The global difference is again significant (t14 = 3.52, p < 0.05. Figure 7). 9 out of 17 listeners show a significant difference.

Test 2 (duration and F0 manipulation)

Intra-speaker response consistency

The two responses to the 44 stimuli show a high correlation (Spearman's ρ = 0.88 (median of all the subjects), p < 0.05).

The subjects can be considered consistent in their responses.

Presentation order

Order of the tests (Tests 1 and 2): A high correlation is obtained between the two groups (ρ = 0.97, p < 0.05). Also, the difference in score is NOT significant (t15 = 2.01, p > 0.05).

Order of the stimuli: Again, a high correlation is obtained (ρ = 0.96, p < 0.05) between the two conditions, and the difference in score is NOT significant (t15 = 0.16, p > 0.05).

Speech rate and pause

Neither the manipulation of speech rate (ANOVA: F(1, 64) = 0, p > 0.05) nor the insertion of pause (F(1, 64) = 0.12, p > 0.05) influenced the scores significantly.

Duration manipulation

The mean scores for French native speakers' productions with and without final shortening are 5.3 and 5.8 respectively. The difference is not significant (t16 = 1.42, p > 0.05. Figure 8). As for Japanese learners, the mean scores are 2.8 and 3.0, with and without final lengthening respectively. The difference is not significant (t18 = 0.52, p < 0.05. Figure 9).

F0 manipulation

The mean scores for French native speakers' productions with and without F0 manipulation are 5.4 and 5.7 respectively. The difference is not significant (t16 = 1.06, p > 0.05, Figure 10). As for the learners, they are 2.9 and 2.8, with and without manipulation. The difference is not significant (t18 = 0.19, p > 0.05, Figure 11).

Duration + F0 manipulation

The mean score (of the 17 listeners) for French speakers' productions with final-shortening and F0 manipulations (= 5.2) is significantly lower than for those with no manipulation (= 6.1; Student's paired t test: t16 = 6.98, p < 0.05. Figure 12). The learners' productions with manipulation of these two factors were not judged significantly better except for the sentence "Il y a une photo de chameaux." (3.0 and 2.2, with and without manipulation; t16 = 2.47, p < 0.05. Figure 13).

Concluding remarks

The results suggest that prosody plays a highly important role in the evaluation of the naturalness by French listeners, and that a native-like prosody could improve significantly the naturalness of utterances with non-native-like segments (3.1.3). Segments play also an important role in the evaluation of naturalness, but not so much as prosody. It is interesting to note that even native-like segments (Seg ca) could receive a low evaluation if they do not conform to the norm of the listeners' standard (in this case, French listeners from France. cf. 3.1.4). It is difficult, however, to evaluate directly the relative importance of native-like segments and prosody from our data (3.1.5). As for intensity (3.1.6), the intensity curve produced by Japanese learners could be one of the sources of non-native-likeness. However, since the score for Pros FR without intensity adjustment is higher than that with adjustment, we cannot exclude the possibility that the manipulation in itself made the stimuli less natural.

Concerning Test 2, it is suggested that the slow speech rate and the presence of pauses, often observed in learners' utterances, are not in themselves important factors in the naturalness evaluation (3.2.3). Final shortening manipulation combined with continuation rise deletion causes to deteriorate the goodness of native speakers' speech, but on the other hand, final lengthening and creation of continuation rise did not improve significantly the non-native-like prosody of learners' except for one sentence (3.2.6). Further experiments will have to be conducted using longer phrases and sentences with more careful manipulations, in order to examine the possibility of improvement by adding final lengthening and continuation rise to learners' productions.

Figure 1 (

 1 Figure 1 (left): Mean scores for Pros FR and Pros JP (30 stimuli each, including all types of segment databases, namely, fr, ca, jp). The large * indicates that the difference between the two conditions is significant. The small * indicates that the score is significantly deviated from 4 (neither good nor bad). The convention holds also for the following figures.Figure 2 (right): Mean scores for Seg jp with Pros FR and Pros JP (10 stimuli each).

Figure 2 (

 2 Figure 1 (left): Mean scores for Pros FR and Pros JP (30 stimuli each, including all types of segment databases, namely, fr, ca, jp). The large * indicates that the difference between the two conditions is significant. The small * indicates that the score is significantly deviated from 4 (neither good nor bad). The convention holds also for the following figures.Figure 2 (right): Mean scores for Seg jp with Pros FR and Pros JP (10 stimuli each).

Figure 3 (

 3 Figure 3 (left): Mean scores for Segments ca, fr and jp (20 stimuli each, including Pros FR and JP).Figure 4 (right): Mean scores for 1) Pros FR+Seg jp and 2) Pros JP+Seg fr (10 stimuli each).

Figure 4 (

 4 Figure 3 (left): Mean scores for Segments ca, fr and jp (20 stimuli each, including Pros FR and JP).Figure 4 (right): Mean scores for 1) Pros FR+Seg jp and 2) Pros JP+Seg fr (10 stimuli each).

Figure 5 :

 5 Figure 5: Interaction between the factors Prosody and Segments (10 stimuli for each condition).

Figure 6 (

 6 Figure 6 (left): Mean scores for Pros FR with (right) and without (left) intensity adjustment.Figure 7 (right): Mean scores for Pros JP with (right) and without (left) intensity adjustment.

Figure 7 (

 7 Figure 6 (left): Mean scores for Pros FR with (right) and without (left) intensity adjustment.Figure 7 (right): Mean scores for Pros JP with (right) and without (left) intensity adjustment.

Figure 8 (

 8 Figure 8 (left): Mean scores for French speakers' productions with (right) and without (left) duration manipulation (18 stimuli).Figure 9 (right): Mean scores for Japanese learners with (right) and without (left) duration manipulation (22 stimuli).

Figure 9 (

 9 Figure 8 (left): Mean scores for French speakers' productions with (right) and without (left) duration manipulation (18 stimuli).Figure 9 (right): Mean scores for Japanese learners with (right) and without (left) duration manipulation (22 stimuli).

Figure 10 (

 10 Figure 10 (left): Mean scores for French speakers' productions with (right) and without (left) F0 manipulation (18 stimuli).Figure 11 (right): Mean scores for Japanese speakers with (right) and without (left) F0 manipulation (22 stimuli).

Figure 11 (

 11 Figure 10 (left): Mean scores for French speakers' productions with (right) and without (left) F0 manipulation (18 stimuli).Figure 11 (right): Mean scores for Japanese speakers with (right) and without (left) F0 manipulation (22 stimuli).

Figure 12 (

 12 Figure 12 (left): Mean scores for French speakers' productions with F0 and duration manipulation (right) and no manipulation (left) (9 stimuli). F i g u r e 1 3 (right): Mean scores for Japanese speaker's production of the sentence "Il y a une photo de chameaux." with F0 and duration manipulation (right) and no manipulation (left) (2 stimuli).

Table 2 )

 2 Intensity

adjustment: Since Mbrola does not take intensity into consideration, we adjusted the synthesized phrases to the intensity curve of the original recording.

Segments

fr Segments ca Segments jp Prosody FR

		FRfr	FRca	FRjp
	Prosody JP	JPfr	JPca	JPjp

Table 2 :

 2

6 Combinations of segments and prosody for the stimuli used in Test 1.

Table 3 :

 3 Manipulation

		duration	no duration
		manipulation	manipulation
	F0 manipulation	both changed	F0 changed
	no F0 manipulation	DUR changed	no change

). of duration and F0 (Test 2)

Table 4

 4

		).
	fr >> ca, jp	8 subjects
	fr >> ca >> jp	5 subjects
	fr, ca >> jp	2 subjects
	others	2 subjects

Table 4 :

 4 Hierarchy of ranking for fr, ca and jp. ">>" means that the difference is significant.

Acknowledgments

I would like to express my gratitude to Jacqueline Vaissière for her guidance, Jean-Yves Dommergues for his advice on the experimental design and statistical analyses, as well as to Cécile Fougeron, Bernard Gautheron, Chakir Zeroual, other lab members, and all those who spent their time participating in the recording and the perception tests.