The following could be the possibilities :-

1) The pipe turning not properly installed. There should be enough transition length from the bend / tee, usually 5D ( 5 times the diameter of the pipe ) length before any termination / next turn to allow transition of the turbulence to laminar flow of the fluid. The turbulence will cause the vibration & water hammering & will not be good to the pipeline in the long run - eventually the joint may give way & pipe may leaks. Additional pipe bracket / support may help to reduce the vibration.

2) The tank cover not properly closed & resulted the water noise to travel within the ceiling space unobstructed.