Strange noise from front

Could be wheel bearing, or something like a rock that got stuck between the rotor and splash guard. It might also be that parts of the brake system are extremely rusty due to lack of use. If you are comfortable working on your car, remove the front wheel and inspect the rotor/hub/caliper assembly.

 

(It's very loud but sometimes you couldn't hear it?) From the timing of it I'd bet you're hearing the electronic squeal of the electrical inverter system that serves the motor/generators and the high-voltage battery. This is completely normal.

 

Yep you can hear the inverter. Usually you can hear a bit of a hum from the pumps plus a very small amount of high frequency squeal from the inverter itself. It definitely should not be "embarrassing" loud though. It should still be quieter than just about any other car with a normal engine.

Can you make a recording of the noise?

 

Someone posted that the inverter on his car was too loud and the dealer changed it (for free IIRC) and the problem was solved. I would bring the car to the dealer for a test drive if you could find a way to reproduce the noise reliably. If not then at least make a recording when it happens and bring the problem to the dealer's attention and obtain a written reciept. Good luck!

 

Let us know the outcome of Toyota looking at your car, as it could assist someone else.

 

Likely the rust is at the back of the brake pads, in between the the pads, shim pads and brake caliper. Perhaps they'd never been inspected? I would suggest minimum bi-yearly check of these. Typically with brake systems all the areas of contact are cleaned and a thin layer of molybedenum anti-sieze compound applied.

There are also pins that allow the caliper to shift slightly, side-to-side. They are more enclosed, and use another lubricant. In my experience I've just checked that they are travelling smoothly, and leave it at that.