Tapping noises are usually from tubing sliding along supports and building surfaces, the tubing should be closely examined to find locations where the metal is touching other parts of the building, then moved away. This does not take much more movement than 1/8″. Banging occurs as high velocity water hits elbows and restictions. Removal of air pockets by careful placement of vents and an air scoop can help. There are some pictures of proper installation on http://www.hydronic.net in the free heating design lessons section.