On Tue, 2 Jun 2009 19:26:26 -0700 (PDT), Paul
wrote:

Our dishwasher "sings" when the motor is running, you could also call
it a medium-high pitch hum has started coming out of the machine (a
Whirlpool Gold Quiet Partner III).

It's about 2 years old. I would think it's the motor, but not sure.
Any ideas anyone?

Time for a new motor/pump assembly, if it is like our Kenmore. Check
to see if you might have a warranty claim, the Sears parts would've
been around $300 if not for a waranty.