Noise when opening door to get in vehicle?

[Pepco]

I notice when I go out to garage to get something out of vehicle, there is a whining noise coming from engine or under vehicle when I open door.
Anyone know what this noise is?

 

[KyLandcruiser]

It’s most likely the brake system pressurizing.

 

[cvx5832LC]

Or fuel pump

 

[EOD Guy]

My guess would be the inverter system...... as the proximity sensors detect the key, the 12v system comes online to power the curtesy lights etc.... when the 12v system computers fire up so does the inverter waiting for a start command / charging the 12v battery.