Function of a phase angle adjustment in a light dimmer
There is a good general description of different types of dimmers here:

http://www.olino.org/us/wp-content/uploads/2009/04/principles_of_dimming.pdf

As Kris commented, I suspect it is a type of inductive dimmer that you have.  If that is correct, then the applicable section in "The Principles of Dimming" would be "Dimming Wire-wound transformers for low voltage halogen lamps."  The adjustment of the phase angle of the light bulbs in this context would correspond to the length of time that the thyristor in the dimmer control must be hard-fired to overcome the inductance of a magnetic step down transformer.  It is a compensation circuit for the lag time required to drive an inductive load.  I do not think it has anything to do with noise control.