Preclear (pre-read) drive sounds like a clock ticking

I'm preparing for a parity swap, so I've begun by running preclear on a new Western Digital Red Pro 16Tb drive. 

It is currently 70% the way through the first pre-read phase (15 hours to this point overnight). I noticed the drive seems to be making a ticking noise once a second, almost like a wall clock ticking. I've read that WD drives can tick every 5 seconds but wasn't sure if this was the same thing. I ran a SMART test prior to starting the preclear and nothing came up during that step. Not sure if I'm over reacting.. !

Thanks

Edited October 20, 20214 yr by KuniD