Ryan’s post below explains the latest is hard drives. But the one thing you do not want to hear is click, click, click.
What you have to understand is the hard drive is one of the few moving parts in a computer. And any engineer will tell you “moving parts are prone to fail”. And when your hard drive fails, more than likely you will hear a clicking noise from it. This clicking is usually in a steady beating pattern. The best advice I can give you is to use the tools you were born with. Listen and if you hear strange noises from your system, get it checked right away by a professional, before failure happens.