Squealing & whining from power supply components on the motherboard is probably one of the most overlooked issues for PC acoustics. Partly it is because the problem is often interactive -- ie certain combinations of components under certain loads produce loud enough noise to be problematic while remaining insignificant with other components & other loads.
Board makers simply don't or maybe cannot afford to spend the time tweaking to eliminate such issues with all combos given the short life cycle of their products. Also, in most cases, this noise is buried under the combined noise from other components in a PC -- PSU, HS and case fans as well a hard drives.
(On that note, I have to say that a serious deterrent to improved acoustics from mainstream component or system makers is that the work environments of both engineers and management is likely to be loud by our standards. So for those guys, anything <40 dBA/1m is probably plenty quiet & they think SPCR is nuts & obsessed.)
Not sure what the solution is at this time.
The worst squealing offender of this kind I ever encountered was a Biostar 200N SFF barebones. The PS components on this thing whined loudly enough to be heard anywhere within a 30ft radius no matter what other components it ran -- including fans at full blast and loud HDDs. It was also dynamic -- mouse movements & screen activity would trigger different types of chattering, clicking, whining, etc. Like a siren chorus!
It was a nightmare.
Biostar would not even respond -- had no response -- to my requests for replacement or a solution for many weeks, I think they thought I was like a hypochondriac... and in the end, despite the nice job they'd done with the rest of this machine, I could not see the point of posting any review. It would have been a total pan; I could not keep it on long enough to do anything with it, it had to be turned off within 10 minutes to save my sanity. I will never know whether this was a true lemon or just like all the other 200Ns.