[Asterisk-Users] sox and wav to gsm conversion quality issue

[Dan]

Hi,

I have some voice prompts in WAV format (PCM, 44KHz, 16bit, mono, bitrate
705kbps) and I want to convert them in gsm format.
Using :
sox file.wav file.gsm
The result is a gsm sound file which when is played the speed is very very
low (something like 5-6 times slower).
Converting first to a 8KHz, 8bit mono wave file, the final gsm file is
correct, but the quality is far than acceptable.
The original file is at a very high quality.

Which is the procedure to obtain the highest quality possible from my
original wav file?

Thanks,
Dan