app_swift-2.0rc1 tts has no sound on Asterisk 1.4.11?

I’ve installed the following on Ubuntu (2.6.16-xenU #1 SMP):

Cepstral_Allison-8kHz_i386-linux_4.2.1
Asterisk 1.4.11
app_swift-2.0rc1
RAGI

Asterisk is loading the app_swift module properly, but nothing is heard when using “Swift(Welcome)” in extensions.conf or “speak_text(Welcome)” via swift.agi.

I’ve also tried the suggestion from: forums.digium.com/viewtopic.php?t=17326 and it still makes no sound.

Any ideas? Debugging suggestions?