From what I can tell by sound, the turn signals on the smart are not flasher/relay operated. A lot of GM cars are going this route, and it sounds very similar. It is a very distinct electronically generated click.
Perhaps there is some sort of adjustment that can be made in software? On some of the more advanced GM models, this is adjustable, so it is feasible - just depending on how they have this thing set up.
Damnit, I need a service manual.