Prana and Agni together produce Naad. It comes from the word which means sound. It pervades everything in the universe and is constant. In its latent form it is the pranav or what we know as Aum. In its expressed form it splits into the seven swaras. There are two kings of Naad. One is Anahat: The intense concentration that happens by contemplating on the Naad and the joy that follows canot be described. Only the guru can understand it. Ahat: The second kind of Naad is the Ahat Naad. It is produced on the groung. Music is related to this Naad. It is also produced inside the body. Ahat Naad inside the body: In the Anahat chakra inside our hearts the wind and the fire hit upon each other and thus Ahat Naad is produced. Ahat Naad- the process: When we desire to speak the Atma inspires the mind, the mind beats upon the fire in the heard, the fire inspires the wind, the wind then inspires rises from the navel and passing through the heart, the throat and the forehead emerges from the mouth as sound. Sound travels from the navel, heart, throat, the mouth up to the head. At each level the Ahat Naad is different. From the navel to the heart is called Mandra. From the heart to the throat is called Madhya. From the throat to the head is called Taar. Depending upon the natural tendencies of the throat of a person the Ahat Naad can be of five kinds: Pushta- well nourished, Apushta- poor nourished, Sukshma- fine, Atisukshma- superfine, Krutrim- Artifical.