This just happened last Friday. I was backing my 2000 i30 out of the garage and I hear this strange rumbling noise like the whale sounds. I thought it was the tires squeaking due to cold. But it wasn't.
I hear it for sure, when I am backing up and turning the steering wheel.
I definitely don't hear it during driving. Other than this the car is running fine.

 

Could be your brakes.. similar thing happened to mine, where the rears would make that sound kinda on a cold startup in the mornings. changed pads and reground the discs and sorted. I think the pads were sticking to the disc.

 

Took it to the mechanic. I was out of power steering fluid.
Got it done for Free!