Prius Buzz sound

Maybe the inverter water pump? It’s hard to tell.

 

Do you have a Movement in the coolant reservoir for the inverter?

Could also be air in the system.

 

is it oem from a dealer?

could also be the brake actuator

 

Most likely your brake actuator pump running. It's located directly behind and below the inverter. It has a pump and an accumulator. Normally, the pump runs long enough to pressurize the accumulator and then turns off. A few cycles of the brake pedal will cause enough pressure drop that the pump will need to run again. If the pump is cycling with no brake pedal motion, then there is likely a leakage problem in the actuator unit itself. Very common problem on the Gen 2. The car will continue to function just fine, until the leakage gets bad enough that the pump has to run continuously, then it will likely code out for low accumulator pressure or something similar.

 

I agree could be the dreaded break accumulator problem.

 

Does the sound cycle on and off? Try putting the car in park with ready light on and pumping the brakes. Listen Carefully you will hear the actuator pump come on. Is this the same sound you are hearing? If it is cycling often and you are not applying the brakes you have an internal or external leak (air leak)in the brake system that needs to be addressed.

 

Video is too short, methinks. I take it the sound you mean is the one that starts about 6.3 seconds in. Does it run for a few seconds like that, and stop, and keep repeating?

If so, yes, it's the brake accumulator pump. It normally sounds a little like a quiet rattlesnake. Yours sounds the worst I've ever heard, makes me think it has already been running too often for a good while now, and now its bearings are also shot.

Running too often probably started with a leaky valve in the actuator. But in a Gen 2, all this stuff is in the same one assembly, so replacing that will solve both the original problem and the secondary one.