although sox is able to play gsm files you have added a patch disabling this capability. I removed the patch, updated to a newer gsm-version (1.0.10) and all things are working fine. Perhaps you should consider to update gsm in the powertools and remove the patch too...
It was taken out because building it relied on the GSM package, which wasn't in the base distro.
I have build sox without the sox-12.17-nogsm.patch and without '--without-gsm'. I could not see any problems (tried without gsm, with gsm-1.0-8 and selfbuild gsm-1.0.10)...
Ooops, wrong xterm... gsm-1.0-8 provided by powertools corrupts the build. Perhaps update to 1.0.10 should be considered.
fixed in sox-12.17.1-1, will be in next rawhide release.