Hi,
in the meantime I managed to solve this problem with a a workaround using the following script:
#!/bin/bash
pico2wave -l=de-DE -w=/tmp/test.wav "$(cat ${1})"
ffmpeg -i /tmp/test.wav -filter:a "atempo=1.2" -vn /tmp/test2.wav # increase speed by a factor of 1.2
firejail --net=none avplay -f wav -loglevel 0 >/dev/null -x 100 -y 50 -vn -autoexit /tmp/test2.wav # play sound in a sandbox
rm /tmp/test.wav
rm /tmp/test2.wav
Cheers
Rosika 