Position: Sit in Padmasana or Sidhasana with hands is Gyanmudra position and elbows slighly bent, make sure spine is straight, shoulders level, head extension of spine .i.e erect, eyes closed and face calm.
Procedure:Breath normally for a few moments. Concentrate on breathing. Now inhale deeply and slowly filling the interior from sahasrara chakra to Mooladhara Chakra. While exhalling slowly two syllables of OM. i.e O &M are to be pronounced. The sound is to be divided in two parts of timind ratio 2 &1 i.e 2/3 part of time pronounce ‘O’ & 1/3 time M.
Concentrate on sound, slowly exhale pronouncing O for 2/3 of time exhalation and imagining sound travelling from Mooladhara Chakra to Anaahata chakra through Sushumna along spinal cord. At this stage close the lips and pronounce M for 1/3 of time of the exhalation. The sound will be like that of humming of a honeybee. Imagine this sound travelling along imaginary line uto sahasrara Chakra and complete the exhalation as much as you can.
Adavantages: This is the basiuc sound calming nervous system and mind, improves concentration and activates spinal cord. It is very helpful in exciting Agya Chakra.