Sorry for a late reply, I've been struggling to keep up lately..  Just
one comment:

> The method returns nil in case the sound is not there. And that method
> needs to be fixed.
> If I want the computer to play a sound and it does not find a sound at
> least I a 'beep' sound.

Which sound plays _could_ be very important; think of a sight-disabled
person, for example.

In that case, I think if the application asks the system to play a
sound that does not exist, an exception should be signaled.  At that
point, the application can handle that exception and play a default
beep sound if that is the desired behavior.  That way test can catch
it easier too, so that mere 'beeps' do not end up replacing the proper
sound in an app simply because it was not caught by testing..

Regards,
  Chris