Some chains and some chainwheel/sprocket combinations will make an engagement noise no matter what you do.

It has to do with the shape of the teeth and the valleys in between the teeth.

Otherwise, noise comes from slight misalignments between the sprocket and the chainwheel.

Sheldon Brown and, I think, John Dace of Businesscycles, both maintain a technical page that gives the different offsets for the various sprockets (more differences than one might think).

If one knows the offset of his or her chainwheel down to a gnat's whisker, he or she can select a sprocket to match...

OR

...one can get a Phil or Miche bottom bracket (assuming a match with one's crankset), both of which allow about 5mm left and right adjustment.

I ride with a Phil bottom bracket, and I bias it about one thread to the right for a dead silent chain.

I have ridden through an early morning herd of deer on two ocassions and they neither "saw" nor heard me.