I've been having this problem for months and can't seem to figure out why Windows is doing this.  I have an Asus PG279Q and an LG 34GN850.  Windows randomly decided to install multiple copies of the PG279Q in Audio Input  and Outputs. Even though the device is disabled and hidden in the Sound control panel.  It NEVER does this with the LG.  At first I thought it was an issue with the Nvidia HD Audio drivers so I uninstalled them a while back and that seemed to work for a bit, then it started again with just the basic Windows drivers installed.  There's no pattern to how this happens either.  It will show one of more of them in Device Manager even while the device is still disabled and hidden in the Sound panel, although randomly it will show up in there as active and half of the two devices that show up from my SteelSeries GameDAC will disappear from the Sound panel when this happens.  Here's an example picture from just now after I rebooted and it went from having two of them to TEN of them just from a reboot!  This is literally driving me nuts and I'm about to punch a monitor.  I used to be able to just re-enable it, reboot, delete the dups, reboot and disabled it again and it would be fine.  Now I just can NOT get rid of them.  They keep coming back in random amounts each reboot.  REALLY hoping someone has seen this before and can offer a fix.
 

 

 

 
Hopefully someone else can chime in.

I suggest contacting Microsoft via the Microsoft forums. Temporarily you can delete all the duplicates except for one entry. Then disable that one item in the device manager. 

rjohnson11
I suggest contacting Microsoft via the Microsoft forums. Temporarily you can delete all the duplicates except for one entry. Then disable that one item in the device manager. 

LOL yeah I've done that, then reboot and it will come back with 10 of them, none of which actually show up in the Sound control panel as active.  I'll try out some of the MS forums I guess.  Never looked for them before.

Post this to the Microsoft forums. 

Just an update for anyone else that might run into this issue.  I haven't actually posted to MS forums yet but some searching around did turn up potential fixes, one of which seems to be working for now.  I had been removing those monitor devices (right click uninstall) but seems I should have actually tried removing the root device which is down in "Sound, Video and game controllers" in Device Manager and is listed as "High Definition Audio Device" (might be named differently if using Nvidia audio drivers).  Once I did that, rebooted, and let it install itself again I have not gotten any phantom duplicates and the system has been up for almost 6 days which is a record since this issue has been going on. 
 
The "Speakers (GameDAC Game)" device had also been getting knocked offline and vanishing from the list even though the "GameDAC Chat" device which is part of the same hardware was not getting knocked out.  I was thinking maybe it was something to do with Oculus being installed because of random error messages in the Event Log but I'm thinking now it might have been related to this issue with the monitor audio devices, or SteelSeries has had a nasty ongoing bug and they just finally fixed it.  Not sure which, but I haven't lost that device yet either in the 6 days up uptime.  We'll see if it lasts.  If the problem comes back I'll definitely make a post on one of the MS forums about it and if I find a better resolution will update here to hopefully help someone down the road that might experience this.