I've had my top-of-the-line Dell XPS serviced(motherboard fully replaced) 3 times because of the coil whine issue, and it's not going away, and Dell said they will not replace it any more. It's one of their most expensive laptops and they can't get such a basic thing right.

Last year when I was deciding which laptop to buy for personal use I ruled out the XPS15 (partially) on coil whine (I'm 37 but thanks to never going to concerts and rarely listening to music beyond half volume I still have decent high frequency hearing).

In the end I went with a Thinkpad and having seen the issues people I know have had with the XPS15 I'm pretty glad I did.