Lower Great Plains implosives

[Herbert Stahlke]

A few years ago I posted a brief comment on implosives that I've heard from
speakers from the Lower Great Plains, a label I've made up for a region
running from Oklahoma and northern Texas up to southern Nebraska and east
into Missouri and Arkansas.  This is not by way of defining an isogloss,
because I haven't surveyed the area and I don't know how far the phenomenon
extends.  I'm basing it on where the speakers I've heard are from.

The phenomenon is that initial voiced stops in stressed syllables become
implosives.  This appears not to happen in consonant+liquid clusters, and it
doesn't happen finally or in unstressed syllables.  Ladefoged mentions that
implosives sometimes occur in English for emphasis and gives the example
"billions and billions" where both /b/ are imploded.  I haven't observed
this myself, and it doesn't sound as if he and I are referring to the same
phenomenon.  However, this is the only published reference I've seen to
implosives in English.  I've also found a reference by Fred Cummins
http://cspeech.ucd.ie/~fred/courses/phonetics/airstream1.html to an
implosive /b/ that he associates impressionistically with a Texas accent.

Does anyone know of other published or www discussions of implosives in
American English (I don't know if Ladefoged's reference is American)?

Herb