XPS 27 AIO (7760) Discrete Graphics Causes Monitor Buzzing

When I disable switchable graphics in the BIOS of my XPS 27 AIO (7760), the Intel Graphics is disabled and only the AMD Radeon 570 is active.  I would prefer this configuration as the Radeon has superior hardware video decode, and the Intel has to allocate system memory to function.  Overall, just a better way to go, given that I don't need power savings on my desktop machine.

However, when I disable switchable graphics, the monitor makes a terrible buzzing sound.  This only goes away when the Dell PremierColor application actives (after user login to Windows) and sets screen brightness to maximum level.  Any other brightness you set in PremierColor causes the buzzing to return.  The screen is way too bright to comfortably use in a dark room in this situation, so no go.  

The buzzing only happens when the Radeon is running in discrete mode.  When the Intel Graphics is active, the screen can be set at any brightness, and there is no buzzing.

Is there any known fix for this issue?