Former Dell XPS 13 Sputnik (9333 model) user checking in.

A decent dev machine for $2K-ish, save for a major flaw: "coil whine"[1]. Very annoying when working in silent environments. Frustratingly random as well - for me, backlight on/off, usb connect/disconnect and scrolling on browsers would change the whine frequency noticably. [2]

It is possible that you can hear something similar from your MBP - however it is very unlikely that this has anything to do with any of the radios.

I miss the good old days when you knew your PC was busy by the HD sounding like a thousand monkeys tap-dancing shakespear.

[1] https://en.wikipedia.org/wiki/Coil_noise

[2] BTW, Dell denies this issue, claiming it was fixed before 9333. Users disagree: https://www.reddit.com/r/Dell/comments/47g46m/lets_investiga...