Southern implosives?

[AAllan at AOL.COM]

I'm out of my league on this one from an Indo-Europeanist who also was my
college roommate. If you have an answer, please reply directly to him as well
as posting it to our list. - Allan Metcalf
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     Although everyone recognizes the vocalic differences between Northern
vs. Southern American pronounciation, I haven't run across any references to
something I auditorily discern in the production of (at least some) Southern
dialects: initial, prevocalic voiced stops appear to be IMPLOSIVE, produced
with a slight lowering of the larynx, rather than with the quite different
plosive initiation used by us northerners.  Such larynx-lowering further
appears to be physiologically coupled with a wider opening of the jaw than
in my dialect. Implosives pop up in various parts of the Indo-European world
and are suspected by some to be involved in early I-E consonant changes.  If
my observations are correct, I would further suspect that such implosive
initiation derives from a Celtic substratum.

     Am I completely off base, or is there reality in my observations?  Are
you aware of such a phenomenon in southern speech?  If this is common
knowledge among you specialists, please forgive the ignorance of this
country bumpkin, and point me to a proper reference.
              - Richard Strand
e-mail: strand at sedona.net

Richard Strand's Nuristan Site:
http://users.sedona.net/~strand