Weird sound when i break lightly on 2006 BMW 650i

I get a weird sound when i break lightly. why is that? i had taken my car into BMW Service last month for a diagnostic on all four tires/breaks, and they said it was fine and normal for high performance breaks to make sounds. However this sound doesnt sound normal.

Asked by for the 2006 BMW 650i
if a brake inspection has not found that the brakes need
replacing from a "wear" standpoint, then you should replace them from a "noise" standpoint. your complaint has nothing to do with safety; it's just a noise. at my BMW shop, would advise all the brakes--pads, rotors and sensors
both front and rear as long as the customer approves the
money. we go thru this all the time with extended warranties; customer has a noise but the warranty will not cover noises; only a failed part. if the customer wants to pay, we will fix anything!
The breaks on this car were recalled. I just bought mine and the (not Beamer) dealership I got it from didn't fix it, so when I had the same problem I took it to the BMW dealership and they fixed the whole shabang for free because of the recall, so I'd get on it if you haven't already, and if you have I'd be a little b!%&#y about paying (at the dealership anyways). GOOD LUCK!