This problem has been pointed out in previous posts (link above)
Dell just replaced the main board of the unit but the problem still exists.
I just also noticed that this noise issue only occurs when the main unit is connected to the keyboard dock.
When the two units are separated, this annoying noise immediately stops and I no longer hear any buzzing sound.
With that said, has anyone tried replacing the keyboard dock unit?
I doesn't seem like it's coming from CPU which is located on the top side of the main unit. This sound seems like it's coming from the very bottom of the main unit of from the keyboard unit.
This exactly represents my problem: the noise seemingly stops when disconnected from the keyboard. Also, I have noticed the sound with sometimes be louder in accordance to me scrolling on the mouse pad or using the touch screen to use the scroll bar.
The noise is definitely coming from the keyboard unit but it seems to be in time with actions on the tablet part, as the other post has noted I've found it frequently happens when scrolling a webpage. I've never found a pattern to when the noise happens though as sometimes it will be making the buzzing noise, sometimes it's quiet and there seems to be nothing which triggers it to happen nor anything in particular that causes it to stop.
The keyboard unit isn't a single part according to Dell, it's made of six different parts which makes it more tricky to get a replacement. I have had my keyboard replaced several times and other repairs done to the tablet but it still makes the same noise and as I was seeing posts from other people with the same problem and fed up of being without the tablet (Dell had spent more time with the tablet than I had), I gave up and just live with it.
Knowledge is Power
Someone I know told me that this issue could be caused by Intel's speedstep technology.
I turned this function off in BIOS and so far (it's only been a day) I don't hear any noise.
I also noticed that Latitude 7350 (Windows 10) does have have "performance mode" under power setting.
I brought this function back by editing the registry.
Change the value of the key CsEnabled from 1 to 0 and reboot.
Then I was able to choose the performance mode.
Again, so far no noise. I'm not sure if this can be the potential solution to this annoying problem.