Frequency Following Response. To achieve synchronization of brain hemispheres, the Hemi-Sync technique takes advantage of a phenomenon known as the Frequency Following Response (FFR) which means that if a subject hears a sound produced at a frequency which emulates one of those associated with the operation of the human brain, the brain will try to mimmick the same frequency pattern by adjusting its brainwave output.
Such meaning is usually perceived visually in the form of symbols but may also be perceived as astonishing flashes of holistic intuition or even in the form of scenarios involving both visual and aural perception.