When driving - there is a HIGH Pitched Whine (even when stopped). It does NOT vary w/ speed if the brake pedal is pressed hard - the whine STOPS???
Vacuum leak? Check around the master cylinder when the engine is running.
Ask your shop to do an experiment. While the car is parked, brake pedal not pressed, engine running, and the noise is occurring, clamp off the vacuum line going to the brake booster, see if that stops the noise. If so, major clue either the vacuum connection at the booster is leaking, or the booster’s vacuum diaphram has sprung a leak.