My NUC7i5BNH has been generating some annoying high frequency noise since day 1. It's quite audible even when it's about ~3000RPM according to the BIOS set up. I have many laptops such as Thinkpad X1, and when idle I don't hear any noises for those devices at all. Is that expected or did I get a defective unit?
Also, whenever I briefly place the unit upside down, the noise is much higher and it sounds like something is getting scratched. Is it also expected? I avoid leaving it upside down and not sure if it's an indicator of the item being faulty.
If the bearings in the blower's spindle are loose, this is exactly what you will hear. It's a high-frequency metal scraping noise. When you flipped the unit over, the loose spindle will then allow the plastic blades to rub on the blower's cowling, yielding this scratching-like noise. Either is an indicator of a blower that will eventually fail. I recommend that you contact Intel Customer Support (ICS) directly and make arrangements to have them replace your base unit. If you want to proceed with this, here is contact information, by geography:
http://www.intel.com/content/www/us/en/support/contact-support.html# @11 Intel Customer Support Contact Information for US and Canada
http://www.intel.com/content/www/us/en/support/contact-support/emea-contact.html Intel Customer Support Contact Information for Europe, Middle East and Africa
http://www.intel.com/content/www/us/en/support/contact-support/apac-contact.html Intel Customer Support Contact Information for Asia-Pacific
http://www.intel.la/content/www/xl/es/support/contact-support/lar-contact.html Intel Customer Support Contact Information for Latin America
You can also try contacting ICS via the http://intelsupportchat.force.com/icslivechat/ics_tech_desktop_ww_english_Chat Intel Customer Support Chat Service, but I believe that this availability of this service is subject to PST TZ hours.
Hope this helps,