I've never heard of capacitors whining. All my SMPSUs that whine do so because of the thin sheets of metal that make up the core (not native English speaker, I'm drawing a blank on their name).

The sheets are supposed to be spot welded to ensure block operation. In later years, this has been phased out, since tightly packing the sheets eliminates vibration (and noise), some using a bit of raisin, some a plastic wrap.

However, shocks during transport, vibration, slight manufacturing errors etc can cause a separation and cause the whine since induced currents in the sheets cause them to attract and repel in-sync with the frequency.

In standard adapters, it was a hum (50-60Hz), but SMPSUs often run in the 10K range, which is roughly whine.

You can either replace the charger or fix it.

IF YOU RUIN ANYTHING I DON'T KNOW YOU.

One can open up the charger and locate the tiny transformer assembly. Once it's exposed, insulation raisin (used on most electronics) can be poured over and through the sheets to stop the vibration.

If you don't have any, SuperGlue and the sorts can be used if you make SURE it has been correctly dried (hint: it's not 5 minutes). Make sure you don't drown the unit, or else it will let current through or heat up and bad things happen.

You know what, if you're not comfortable with modifying stuff that works at high voltage, just buy another charger. Get one of those USB universals and use the cable. Or the PC.