Comment 6 for bug 178256

There may be no sound in psi because "play", psi`s default player, is missing a lib.
Without this it looks like this:
{{{
play /usr/share/psi/sound/chat1.wav
play soxio: Failed writing `default': unknown file type `ao'
}}}

After
{{{
sudo aptitude install libsox-fmt-ao
}}}

an retry will look like this:

{{{
play /usr/share/psi/sound/chat1.wav
Input File : '/usr/share/psi/sound/chat1.wav'
Sample Size : 16-bit (2 bytes)
Sample Encoding: signed (2's complement)
Channels : 1
Sample Rate : 44100
Comment : 'GoldWave (C) Chris S. Craig, http://www.goldwave.com'
}}}

Psi`s sound is not working because the sox default device driver is not installed, when you install sox.
As it was already said "Please consider making "aplay" the default player used in the Ubuntu Psi installation."