Keeping the power turned on to the icemaker before the water line is connected can damage the icemaker.
You will hear the sound of ice dropping into the bin and water running in the pipes as the icemaker refills.
The icemaker water valve buzzes as the icemakers fill with water. If the icemakers are turned on, they will buzz even if they have not yet been hooked up to water.
To stop the buzzing:
Turn icemakers off by refering to Control Panel in the Operation section.