I forgot to say that my environment is ubuntu SERVER.

Usually the command I use to generate my mp3 is :

cat "test.text" | sapilektor -a -r -s "1.0" -p "1.0" -v "celine" - | sox -t raw -e signed-integer -c 1 -r 22050 -b 16 - -t wav - vol "1.0" bass "0" treble "0" contrast "0" | lame --preset voice -r -m m -s 22050 - "test.mp3"