cracking noise from left front brake

[CITMAN]

when i apply the brake pedal when stationary on my zx I can here a loud cracking noise which can be felt through the floor on the car. it appears to come from the passenger side brake. If i put my hand on the caliper with some pressing the brake pedal i can feel it and here it. i persume its from the caliper. the funny thing is that when the handbrake is applied and the suspension at the back goes down a bit it doesnt make the cracking noise on pressing the brake pedal,