Vowel substitution patterns in Japanese speakers’ English

Takehiko MakinoChuo University, Tokyo, Japan

Preliminaries

Background Vowels are one of the most difficult parts of English

pronunciation for Japanese speakers. This obviously reflects the difference between the vowel systems of the two languages: Japanese has only five vowel phonemes while American English has eleven monophthongs and five diphthongs.

However, it is too simplistic to assume that Japanese speakers just reduce English vowels to their own five vowels. Many learners do acquire parts of the vowel system.

The problem is that individuals differ as to the parts they acquire. This results in the heterogeneity of the problems they have in their vowel production, which gives instructors difficulties in correcting them.

To my knowledge, there has been no systematic observational study on English vowel substitution patterns by Japanese speakers. This is understandable because such a study would have required large-scale databases or corpora of Japanese learners’ English pronunciation.

The purpose of this study To observe the vowel substitution patterns of American

English vowels by Japanese speakers. The material I observed is part of English Learners’ Speech

Database (Minematsu et al. 2002), a collection of more than 70,000 recordings read aloud by more than 200 Japanese university students.

The body of data I used is the same as I used in a pilot study of corpus analysis presented at PTLC2007 (Makino 2007).

Methods of present study I chose seventy-five recordings from the phonemically-

balanced sentence sets. They are all read by different speakers.

I transcribed each recording phonetically by listening to it and referring to the waveform, spectrogram and fundamental frequency trace made by Wavesurfer version 1.8.5

Efforts were made to make as narrow segmental transcriptions as possible

I compared the transcribed vowels with their English norm by looking at the transcriptions one by one. The number of vowel token was 771.

The Japanese vowel systemThere are five vowel phonemes: /i, e, a, o,

u/. The phonetic realizations are approximately [i], [e̞], [ɐ̞], [o̞], [ɯ̈ ~ ɨ̈]. Note that /u/ is unrounded and /a/ is not fully open.

Combinations of vowels make diphthong-like units, but /ei/ and /ou/ are usually smoothed to [e̞ː] [o̞ː].

The American English vowel system The norm of American English vowels adopted in

this study is that I described in Makino (2005).

The inventoryMonophthongs: /i, ɪ, ɛ, æ, ɑ, ɔ, ʊ, u, ʌ, ɚ, ə/Diphthongs: /eɪ, aɪ, ɔɪ, aʊ, oʊ/R-diphthongs: /ɪɹ, ɛɹ, ɑɹ, ɔɹ, ʊɹ/

The findings

“Easy” vowels The easiest vowel of all is /i/. 73 out of 80 tokens

(91.3%) are pronounced [i].

/ɛ/ is also easy. 25 out of 40 (62.5%) are [ɛ] and additional 12 (30%) are [e], which is close enough to the English norm. Together they make up 92.5% of all /ɛ/ tokens.

25 out of 32 tokens (78.2%) of /aɪ/ are pronounced [aɪ, ɐɪ, ɑɪ]. Obvious errors are [ɐ, ɪ, a, ɛi] , which could have been caused by misunderstandings of spelling-to-sound correspondence.

Although their tokens are too few to be significant, /ɔɪ/ and /aʊ/ also seem to be easy. 8 out of 10 /ɔɪ/ are [ɔɪ] and additional 1 is [oɪ].

9 out of 15 /aʊ/ are [ɑʊ, ɐʊ]. [ɑɯ] (1 token) and [ao] (1 token) also seem to be acceptable. Together they make up 73.4% of all tokens.

“Tough” vowelsThe toughest of all is /ɪ/. Only 28 out of

133 tokens (21.1%) are pronounced correctly. 90 tokens (67.7%) are merged to /i/.

/æ/ is also difficult. The correct pronunciation is only 14 out of 38 (21.1%). Errors are [ɐ] (36.8%), [ɑ] (15.8%), [a] (13.2%) and so on.

/ɑ/ is presumably influenced by its regular spelling <o>. Out of 32 tokens, 15 (46.9%) are [ɔ] and 5 are [o]. Note that the romanized spellinjg of Japanese /o/ is <o>.

/ɚ/ is correctly pronounced in only 7 out of 44 tokens (15.9%). 36 tokens are pronounced without r-coloring (16 are [ɐ], the usual realization of Japanese /a/).

/oʊ/ is pronounced in monophthongs [ɔ, o, ɔ̈] (22 out of 32 = 68.8%) more often than diphthongs [oʊ, ou, ɔʊ] (4 tokens = 21.9%). This is clearly influenced by the smoothed realization of Japanese /ou/.On the other hand, 71.4% of /eɪ/ (30 out of 42

tokens) are pronounced correctly as a diphthong. (Other tokens are monophthongs.)

“Variable” vowelThe most variable vowel of all is schwa /ə/.

In addition to a correct realization (47 out of 115 tokens = 40.9%), I found nineteen different realizations. This seems to be influenced by the sound’s variety of spellings.

R-diphthongsThere are too few tokens of r-diphthongs

( 5 /ɪɹ/s, 6 /ɛɹ/s, 8/ɑɹ/s and 17 /ɔɹ/s) to make a significant observation.

However, it is to be noted that r-offglide is observed in only in minority of the tokens. 3 in case of /ɔɹ/ and 1 on the other vowels.

“Postvocalic /r/” seems to be one of the most difficult sound for Japanese speakers.

Other vowels /ɔ/ seems moderately difficult. 21 out of 32

tokens (65.6%) are pronounced correctly. 3 diphthongal tokens are observed.

/ʌ/ also seems moderately difficult. 12 out of 19 tokens (63.2%) are pronounced [ɐ], which could be seen as acceptable pronunciation.

I cannot decide whether /u/ and /ʊ/ are difficult or not.

29 out of 40 tokens (72.5%) of /u/ are [ʉ], whose acceptability I cannot decide. I found only 3 completely correct [u] tokens.

9 out of 15 tokens (60%) of /ʊ/ are [ɨ]. I do not see if this is an acceptable realization. In any case, tokens are too few to be significant.

Conclusion

This study have revealed to some extent which English vowels are difficult for Japanese speakers and how they mispronounce them.

In some vowels, tokens are too few to make a significant decision.

It is necessary to investigate a larger data set, which will make a more reliable result.

ReferencesMakino, T. (2005) Nihonjin no Tame no Eigo Onseigaku Lesson.

[Lessons in English Phonetics for Japanese Speakers.] Tokyo: Taishukan Publishing Company.

Makino, T. (2007) A corpus of Japanese speaker's pronunciation of American English: preliminary research. Proc. Phonetics Teaching and Learning Conference 2007 (PTLC2007).

Minematsu, N. et al (2002) English speech database read by Japanese learners for CALL system development. Proc. Int. Conf. Language Resources and Evaluation (LREC2002), pp.896-903.