Ancient rishis who studied the breath found it to have four natural sounds:
- A - an inhalation through the mouth
- Ha - an exhalation through the mouth
- U - an inhalation through the nose
- Hum - an exhalation through the nose
The rishis noticed that when the breath becomes more labored through physical activity or strong emotions, the additional “H” sound of the exhalation is intensified. This “H” sound is thought to create a downward force from the throat, which dilutes pranic energy. Conversely, when the breathing is calm, the “H” sound is reduced and the pranic energy is retained, promoting feelings of greater peace and relaxation. Therefore, Ajapa yoga encourages the practitioner to dissipate and reduce the “H” sound of the exhalation.
This can also be understood in relation to the universal sound Aum, often written as Om. The four natural sounds of the breath can be broken down to “H,” “A,” “U” and “M.” By minimizing the “H” sound, the yogi's breath makes only the sound of Aum, thus potentially bringing them to a higher state of consciousness.