Record sound files for use in asterisk
i keep on forgetting the procedure, so i write it down here as a reference
i usually record the message for my Asterisk PBX using Audacity. I then export the sound as normal WAV file. Then i simply use the tool "sox" to convert it from WAV to GSM
sox myfile.wav -r 8000 -c1 myfile.gsm resample -ql
it's as easy as that!