Rattling data Monster

Video at Amazon.com See the HDD I bought about a month ago. She walked quietly in a Fantec USB 3.0 + eSATA enclosure. It was connected via an eSATA controller (Express Card34) Equip to a MacBook Pro.
It is only slightly "louder" or less quiet than the 1.5TB and 2TB versions, which lies on the additional platters and can be neglected. It's perfect living room Suitable!

Overnight I have it with data packed ... Now she does in the IDLE state, so idle a permanent, clack sound.
Both in the housing, as well as with an external power supply (see the video) it sucks. So it is not the system that tries to written data.
While I wrote this review has disappeared the sound. So with data write again full and see if it mucks again.
If it does so, it goes back again!

That's my first problem with WD. Therefore, and because it otherwise a good figure makes 4 out of 5 stars.