Like the title says....I got alternator whine that has recently developed.

Some details:
99 Mercury Marquis 4.6 2V bone stock. Around 134,000 miles.
I do the majority of maintenance.
Original alternator.

What's been done recently:
Serpentine belt replacement
Belt tensioner replacement
Idler Pulley replacement
Voltage regulator replaced in alternator
Bearings replaced in alternator

Numbers and tests:
Battery voltage after sitting overnight is 12.4 Volts
Alternator voltage when vehicle running is around 13.4 Volts
Increasing RPM's and holding stable voltage is around 14.0 Volts
After driving the alternator case temperature at the hottest point is around 215F
Unplugging the alternator stops the whine.

Symptoms:
Alternator whine most if not all the time. (Hard to tell sometimes when driving such as on the highway.)
Zero problems electrically and no dash lights or codes. No radio issues.

What's wrong with my alternator?