Are you driving a Rolls Royce or the entry level CT200h by Lexus?This is exactly what they told me, but it is NOT acceptable! Passengers in a Lexus should never be freaked out by a sound coming from your breaking system! The factory recommended a double flush of the breaking system, to try to eliminate the sound. I would expect this sound from a cheaper brand; but with a luxury brand, strange noises like this are unacceptable.
I will let you know if the double-flush fixes the noise.