Heads crazy, noisy, but no errors at all

Hello,

My hdd model is an Hitachi deskstar 5k3000 HDS5C3030ALA630, 3380 hours / 313 power cycle count

I was very happy with this HDD, it has a very low noise and very low vibration.
And I always used it for backups, it was not running continuously.

The format type is normally HFS+ (used in a mac mini external enclosure from Verbatim)

Last week I needed to do a partition cloning of windows 10 and used it in NTFS type. All was ok.

Then I returned to my mac and reformat it in HFS+ but before that I noticed some rare noises.
I copied some files, all was ok but when idle the repetitive noise began again.

I have done a secure format, it took a lot of time to complete but it was done with none errors and any noises while working. After this, when idle, the noise returned.

I leave the noise recorded here:
https://dl.dropboxusercontent.com/u/2273204/Hdd%20Hitachi.m4a
The silence moment is when copying a file.

And report here:
https://dl.dropboxusercontent.com/u/2273204/HDD%20Hitachi/Hitachi

Has anybody noticed this??

Thanks in advance