Apart from the codec patches for ETSI codec i cant find any other voice decoding source code in osmocom-tetra trunk. Neither seems to have entered you in the AUTHORS file.
FAQ on the site says:
"Can your software actually play the voice signal?
Currently we have no support for that. However, a yet unreleased proof-of-concept version exists."
Why this secrecy for publishing source to decode unencrypted networks?. Have osmocom been threatened by the tetra manufacturers? Would damage sysmocom commercial interests
Just in case, I have sent my "proof of concept" modification for voice decoding to the authors of Osmocom TETRA for proper integration a while ago. As far as I am aware the current source code should be able to decode voice or at least contain the instructions how to do it (the ETSI reference codec is most certainly not included for copyright reasons).
Best regards, Dieter -- Dieter Spaar, Germany spaar@mirider.augusta.de