The heater blower fan is behind the dash near the glovebox area if it makes a little noise when the engine is first turned on or the car first has the key turned on then there may be a leave caught in the blower motor or the brushes in the motor may be going out. It is easily taken out to inspect from the passenger footwell area.
Back to the drawing board - fan is out but it's not the problem - my husband says it sounds like a chattering magnetic coil - can't hear it under the hood, only in the car - and directly in that passenger area. Any other ideas are so welcomed!!!
I have this problem with my rabbit and I believe it is the pump for the windshield washer fluid. Mine makes the noise when it starts and also when going from a forward gear to reverse or vice versa but not when switching between forward gears, it also makes the sound when spraying the windshield hence my "diagnosis". I dont know for sure if this is the culprit but that is my thought, hope it helps. No I have not done anything to fix it.