Introduction: In the article on Tratak we’ve already mentioned the value of stimulating the brow chakra. A very powerful adjunct to the method of physically feeling subtle sensations in the brow area is the use of voice vibrations focused there as well.
There is a real science to the use of specific mantras in relation of each of the etheric/astral chakras, but that is an extensive subject that is more completely developed in books dedicated to that subject.
All you need to do now is to “hum”—vibrate the sound of Om (A"aa-ooo-uuu-mmmm" without the break between syllables that we’ve indicated with dashes for clarification). The most important segment is the final uuu-mmmm, which should be barely audible but distinctly felt in the brow just above and between your eyes.
Feeling the vibration is important, and requires some effort at first. You will also need to experiment with the tone and the “source” of the sound. It works best to initially pitch the voice below your normal level, and to feel it coming from the back of the throat moving forward and upward to center on the brow—feeling the vibrations right in the bone structure of your skull.
The goal is to feel that vibration not only in your skull but in your vision.
Summary of Purpose & Benefits: Mantras are exceedingly simple to use and very powerful in their effect. They can be employed over the entire body and for a number of purposes.