Sound can only come from a vibration be it a drum, our vocal cords, or brake pads. You can not have any sound---period without a vibration. The squeal is the pad vibrating in the caliper---bad hardware, no backing plate/ shim would be what I would look at first. Like Blast Chamber said, some noise at the start when light rust is not even on the rotor causing the hard (semi-metallic) pad to bounce---again vibrate is normal. Start with brake shims; I used "tons" of them in my repair shop---they work. Also, anti-squeal to the back of the pad to help hold it in place. Too many have used this pad---people even want them from you now---this can be fixed. Good Luck!!! Jimmy