You aren't substituting the name of the audio file into your OS commands, so it can't possibly work.
You'd need something like:
os.system('xdg-open ' + audiofile)
This assumes that you have a default application associated with .wav
files, which of course you can test by trying your command manually.
You might also want to check the return value of os.system
for an error code, rather than relying on exceptions.