The correct command line option to specify a audio output device is -O followed by the
device name. Next issue you may encounter is that unless your sound card natively
supports an 8000 sample rate, you're actually going to want to use
"plughw:0,0" instead of "hw:0,0" for the device name. Normally
however, leaving things unspecified will be fine (in which case it uses
"default").
All this aside, I wouldn't actually worry about getting audio working until you know
the software is tuned properly, decoding the control channel successfully and actually
trunking. Only then will audio be evident in any form. Look for changing status messages
in the lower left of the scope.py window.