>In my opinion, a voiced dental or coronal or alveolar stop should have a
physical definition >that is independent of the perception of any
individual.
Oh they do have those definitions, but that does not stop a person's
language from interfering with their perception of the sound. For example,
it is fairly common experience that English speakers will hear French
unaspirated initial /p/ as /b/. My own dialect has a very clear phonetic
distinction between the vowels of <pig> and <peg>, but that does not stop
speakers of other dialects mis-hearing them. My perfectly plain voiceless
/W/ is sometimes heard by UK speakers as /kw/. This is fairly standard
stuff, isn't it?
Peter