I am still studying this - and right now it seems to be about the shape of the numbers - that 3-6-9 describes a spiral from all angles, and it is the KEY to the UNIVERSE, as per Nicola Tesla...
It is so many things - DNA, the Golden Mean, etc but perhaps it is also the way to get to the 4th Dimension which IS vibration...
Again, not sure how yet... but still studying it.
here is a post regarding the solfeggio frequencies which all reduce to 3-6-9 http://www.spiritualcoach.com/health-and-wellness/solfeggio-frequencies-the-numbers-3-6-and-9-2148/