Clicking or ticking sound from disks every minute!

I have one of these drives in my PC's removable drive caddy, and i've noticed an audiable "clicking" noise from time to time too. I believe this is the heads on the disk "parking" themselves and then "unparking themselves" when the drive is accessed. It sounds unnervingly like the sound a drive makes once it's dying, i know. But check the SMART data for the drives in frontview and if there is nothing worrying there, just learn to ignore it as I have had to train my mind to do.