It is also called Pranav because its sound emanates from the Prana (vital vibration), which feels the Universe. The scripture says "Aum Iti Ek Akshara Brahman" (Aum that one syllable is Brahman). When you pronounce AUM:A - emerges from the throat, originating in the region of the navel U - rolls over the tongue M - ends on the lips A - waking, U - dreaming, M - sleeping It is the sum and substance of all the words that can emanate from the human throat.
