The IETF has recently put out a request for an audio codec. This may strike some of you as remarkable that anyone would need another audio codec since, at the time of this writing, we have cataloged 137 audio codecs via the MultimediaWiki. You have to give the request some attention, though– it acknowledges that there are already lots and lots of audio codecs in existence and explains why each category is unsuitable to the goals of the request. I’m not going to be the one to audit every one of those 137 codecs and identify why each is unsuitable for the outlined goals.
I am a bit concerned about some of their stated goals, such as the very first one: “Designing for use in interactive applications (examples include, but are not limited to, point-to-point voice calls, multi-party voice conferencing, telepresence, teleoperation, in-game voice chat, and live music performance).” Generally, one of those examples is not like the others (unless, perhaps, “live music performance” refers to a cappella singing. Then again, the request later states that optimizing for very low bitrates (2.4 kbps and lower) is out of scope.
there are also acm codecs which are undiscovered:
http://wiki.multimedia.cx/index.php?title=Category_talk:Audio_Codecs