On the 767/757 the flaps and slats are driven ( normally ) by hydraulic Power Drive Units , 3 on the 767 and 2 on the 757. These in turn drive torque tubes to the canoe fairings you see on the wings, where screwjacks actually move the flaps. You probably heard the PDU's.
GJB: the racket on the 146 is completely different - it's caused by a high-energy escape of airflow between the flaps and the fuselage wall.