2013 Fit Brake Whine At High Speeds

Trying to determine what could cause a whining sound coming from the area of the booster/master cylinder when I apply the brakes, but only if the car is moving faster than about 40 MPH. I'm guessing at the location of the sound because I obviously dont have my head in the engine compartment when doing 40. I have a few friends who might try it though... Anyway, I know its not pad noise because if I maintain braking until I come to a complete stop, the noise still continues for a few more seconds. Its only there when I am putting pressure on the brake pedal and when the noise stops it wont come back until I get the car over 40 MPH and apply the brakes again. :dunno: :screwy: It sounds like a very small electric motor or pump, or maybe a relief valve letting off pressure. Clueless, party of 1!!