My dishwasher makes a very quiet, almost unnoticeable hum when it is off. Opening and closing the door does not stop the noise. However, if I unplug the dishwasher and plug it back in, the noise stops until after I run the next cycle when it starts again.

I thought the noise might be the pump running, so I put some water inside the dishwasher to see if it would pump it out, but it did not.

When it makes the humming noise I can feel the door handle vibrate ever so slightly.

I'm thinking it might possibly be the fan on the door, but I don't know how to check for this.