En réponse à "Thomas R. Wier" <[log in to unmask]>:
> Generally not. There are languages that have voiceless vowels
> as allophones (e.g. Japanese) and perhaps even some that have
> voiceless vowels phonemically distinct from voiced vowels.
I think some Northern American languages have phonemical distinction between
voiced and voiceless vowels. I remember reading an online grammar of such a
language where two suffixes with different meanings differed only by the voice
of their vowel. But I just don't remember which language it was...
Take your life as a movie: do not let anybody else play the leading role.