High pitched squeaking noise...

Does the noise sound like the Vehicle Proximity Notification System which is demonstrated in this video....? If so, it's normal.

 

Just TODAY I purchased my 2013 Prius Model 2. While test driving with the dealer and talking and turning the radio and things on and off I didn't notice anything. However, on the drive home, the super high frequency whine became painfully obvious. It's in dog-whistle range....and I can hear it. And it's PAINFUL. Seriously stressful and headache inducing. It gets worse whenever I step on the break. Not sure what to do. It's horrible!!

 

My 2 week old Prius 4 does this too. I just figure it's the regenerative brakes, etc. working.

 

exactly my experience.
the noise causes my ears to ring when i get home.
something has to be done about it
i have less than 100 miles on my car

 

You can unplug the proximity alert system pretty easily. It's located in the fender well below the drivers side headlight. You will need to open the access panel below the car just behind the bumper.