Hey,
Just looking through the ADRES for the A320......there is quite alot of things in the middle of the plane from...flap-right-hand-gearboxes to fuel pumps....so theres a lot of things to make a noise..
Been on an A320 recently...the brakes to tend to make a clunk as they are applied...you can feel it quite alot in the cabin whilst braking...the parking brake makes a noise as it goes off....
aah the joys of the Airbus......
Regards,
Matthew