Mantras are a set of words said to have mystic vibrations. There’s a lot of work on mantras, and it has shed light on some of the most fascinating and detailed science of how the brain functions, and how can one influence / regulate it.
Firstly what is a mantra? We all know mantra is a sound or sound sequence that is repeated. In many or even most cases, the mantra did not have a literal or word meaning. But the sound has significance.
What is the significance of the sound?
When human brain functions, it generates waves that can be recorded and measured. Waves are classified by their frequency, which is measured in Hertz or Hz. Typically four kinds of waves are recognized by neuroscientists-
- Beta waves. 14 to 20 Hz, found when the brain is functioning normally thinking, problem solving etc
- Alpha waves 8 to 13 Hz, during light meditation, thinking. With this state of brain, body feels relaxed, secretes parasympathetic hormones for relaxation.
- Teta waves 4 to 7 Hz are recorded in meditation by practitioners. Awareness of body is very little, mind feels free and gets into deep relaxation.
- Delta waves 1 to 3 Hz are in unconsciousness, and very deep states of meditation rarely achievable.
- These for states are normal, and a fifth state, gamma waves are recorded in Tibetan monks only. It is believed normal as neurons can not produce such waves.
This is exactly parallel to brain function described by the scholars who designed most mantras. The old literature supports brain functions in four states – wakefulness, sleep, deep sleep or deep meditation, and the last state called turiya or the fourth state can make brain so stable as to get out of body experiences. 
When we speak, speech has a frequency. Brain starts to align with the frequency it hears. This is why agitating voices agitate and calm voices calm down.
What is the significance of a mantra?
Mantra is a sound sequence, which when pronounced correctly will come out in frequency range of 3 to 7 Hz. When brain hears this, it tends to move into meditative state. The best person to hear is from the practitioner himself, as the vibration that affects brain the most is our own.
A 15–20 minutes session each day relaxes the brain completely, secretes hormones in the body that relax it.
The reason most mantras don’t have a literal or word meaning is because these were sounds heard by advanced practitioners in deep states of meditation, which later they taught as ways to reach that state.
The universal mantra, Om has a frequency of 7.3 Hz, which is also the same as earth’s sound dur to rotation on is axis. It is said this mantra puts one in a state resonating with earth and therefore getting its energy after a lot if practice this can be achieved.
The purpose of reciting mantra is to send the brain in this state of relaxation.
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Article Source: F Shant