Unvoiced vowels in katakana: special case?


When foreign words or proper names are used in Japanese, some modifications
are necessary, in particular a lot of vowels are introduced. E.g. 'plastic'
(two syllables) becomes プラスチック (five). In this case, it is not that the three
/u/ will turn out to be unvoiced: this vowel was chosen precisely to yield a
pronunciation not too different from 'plastic' -- it is unvoiced by design so
to speak.

So are there either formal rules or a tendency to silence these vowels to be
as close as possible to the original? Or is there no special status?




The devoicing of vowels in Japanese is determined by the internal phonological
environment of Japanese words. There is a relatively small set of
circumstances under which it happens, e.g. [the vowels 'i' and
'u'](https://www.japaneseprofessor.com/lessons/beginning/pitch-accent-and-
vowel-devoicing/) are often devoiced between two voiceless consonants (くつ) or
[following a voiceless
consonant](https://en.wikipedia.org/wiki/Japanese_phonology#Vowels) at the end
of a word (です). With such limited scope under which devoicing is possible, it
is very unlikely that this plays any significant role in the decisions about
kana choice for loanwords. There are simply not enough conditions at play to
manipulate the word in an attempt to preserve its original phonemic
expression. Other factors are more likely to play a decisive role.

It is certainly an interesting area and there are some threads on the site
which discuss the factors which might influence the choice of kana. I think
you will find them of interest. See below:

  * [What changes are made to the pronunciation of gairaigo?](https://japanese.stackexchange.com/questions/2147/what-changes-are-made-to-the-pronunciation-of-gairaigo)
  * [Who decides what katakana will be used to form English loan words?](https://japanese.stackexchange.com/questions/5284/who-decides-what-katakana-will-be-used-to-form-english-loan-words)
  * [Different transcriptions for words with related origin](https://japanese.stackexchange.com/questions/3275/different-transcriptions-for-words-with-related-origin)
  * [What is the more common pronunciation for the r­ōmaji letter Z in Japanese?](https://japanese.stackexchange.com/questions/6018/what-is-the-more-common-pronunciation-for-the-r-%c5%8dmaji-letter-z-in-japanese#comment15341_6018)

