How to Convert wav to gsm on linux
This is a easy way of converting all the wav files in the working directory to gsm format - useful if you want to record your own IVR prompts for asterisk..
for i in *.wav do sox $i -r 8000 -c 1 $(basename $i .wav).gsm resample -ql done
save the file as wav2gsm.sh, or add a shebang and save as wav2gsm and then call it like this:
All the wav files will be converted over in an instant...
If the volume is too high, you can reduce it, article "How to reduce the sound volume of a wav file"