On 05/07/2014 02:06 AM, cctalk-request at 
classiccmp.org wrote:
  Date: Wed, 7 May 2014 00:55:45 -0600
 From: Eric Smith<spacewar at gmail.com>
 Cool project! I'm interested in hearing how well V.32bis
 QAM modulation (14.4 Kbps) works over VOIP, since a lot of
 VOIP applies compression schemes intended specifically for
 voice. On uncompressed PCM, or PCM with only basic
 companding (mu-law or A-law) it should work fine, since
 that's what has most commonly been used by the phone
 companies for carrying domestic POTS calls. International
 voice calls often used more compression, which at the very
 least could be expected to increase the error rate. Eric  
I have Charter VOIP, and
have used a 14.4 modem for faxes with
no trouble.  That may not tell you a whole lot, but at least
it works
in that limited mode.
Jon