Why when I brake at low speeds do i hear a pop noise from the front end? on 2006 Volvo S40

I own a 2006 s40i with 73K miles. When I am pulling out or starting off at low speeds and then break ( like at a stop sign) I hear a pop noise after I depress the break pedal? What could be the cause? it occurs all the time.

Asked by for the 2006 Volvo S40
loose frt caliper or worn hardware