# COMPRESS RECORDS IN ASTERISK FROM 128 kbit/s TO 13 kbit/s sox src.wav -r 8k -c 1 -e gsm dst.wav # BULK COMPRESSION find `pwd` -name "*.wav" -type f | sed s'/.wav//'g | while read line; do sox $line.wav -r 8k -c 1 -e gsm $line.WAV; rm -f $line.wav; done