Odd whining noise related to brakes, new 2015 Prius Five

Today as my wife was pulling into the garage I heard a fairly loud, intermittent "screech" or whine coming from under the hood. I had her turn off the car, then start it again -no noise. Then I had her back out and pull back in, heard the noise. "It happens when I press on the brakes" said she. I had her do so, and, sure enough, there it was. No noise when the pedal is depressed, but as soon as the pedal is let off, the noise cycles on for a few seconds and then stops. I figure it's some sort of brake booster pump going bad. I was quite crestfallen because we have only had the car for 2 weeks and like it so much. Anyone know what this is?
Thanks!

 

Thanks everyone who took the time to reply. The noise is certainly some kind of brake hydraulic pump as it only happens after the brake pedal is depressed and released. The plan is to take it to the dealer and get their take on it. I think it might be "normal" noise but inside our garage it almost sounds like grinding metal to me. Therefore my concern. I'll write back when I learn what they say.

 

Updating topic 4/21/15: noise seems to have disappeared. Cannot reproduce the noise so I guess it fixed itself - or maybe it was paranoia on my part. Thanks all for taking the time to respond!