[dietpillxanaxaxx]

Just Googling the wiki for 'wave mechanics' and finding some interesting physics information related to this seemingly meta-physical phenomena:

Interestingly, both 'synching' and 'phasing' are commonly used terms.

Perhaps I experienced a "phase offset modulation" which most closely resembles this dual vibration feeling I had:
http://en.wikipedia.org/wiki/Phase_offset_modulation

others:
http://en.wikipedia.org/wiki/Phase_synchronization
http://en.wikipedia.org/wiki/Sine_wave
http://en.wikipedia.org/wiki/Category:Wave_mechanics

si