Why does the brake actuator make a clicking/ knocking sound when using brakes

If you are hearing a noise depressing the brake pedal even when starting the car, it's something that warrants having a local technician listen without and determine the likely cause even audibly. My initial thought was that bake pads may be moving a bit, but if it happens with just depressing the brake pedal to start the car, it's unlikely to be the source of your noise.