[TTY15]

This piper.conf works for me:

GenericExecuteSynth "if command -v sox > /dev/null; then\
        PROCESS=\'sox -r 22050 -c 1 -b 16 -e signed-integer -t raw - -t wav - tempo $RATE pitch $PITCH norm\'; OUTPUT=\'$PLAY_COMMAND\';\
    elif command -v paplay > /dev/null; then\
        PROCESS=\'cat\'; OUTPUT=\'$PLAY_COMMAND --raw --channels 1 --rate 22050\';\
    else\
        PROCESS=\'cat\'; OUTPUT=\'aplay -t raw -c 1 -r 22050 -f S16_LE\';\
    fi;\

GenericRateAdd 1
GenericPitchAdd 1
GenericVolumeAdd 1
GenericRateMultiply 1
GenericPitchMultiply 1000

GenericExecuteSynth "printf %s \'$DATA\' | piper --length_scale \`echo \'($RATE * 0.65) + 1\' \| bc\`  --sentence_silence 1 --model ~/.local/share/piper/voices/$VOICE --output-raw | aplay -r 22050 -f S16_LE -t raw -"
# only use medium quality voices to respect the 22050 rate for aplay in the command above.

GenericCmdDependency "piper"
GenericCmdDependency "aplay"
GenericCmdDependency "printf"
GenericCmdDependency "bc"
GenericSoundIconFolder "/usr/share/sounds/sound-icons/"

GenericPunctNone ""
GenericPunctSome "--punct=\"()<>[]{}\""
GenericPunctMost "--punct=\"()[]{};:\""
GenericPunctAll "--punct"

#GenericStripPunctChars  ""

GenericLanguage  "en" "en_US" "utf-8"


AddVoice        "en"    "MALE1"         "en_US-libritts_r-medium.onnx -s 7"
AddVoice        "en"    "FEMALE1"       "en_US-amy-medium.onnx"

DefaultVoice    "en_US-libritts_r-medium.onnx -s 7"

Look at

$RATE * 0.65

And speechd.conf as in above links.