"OM" the First Sound of Creation
The name Omkara, (Sanskrit: the syllable om) is taken as a name of God in the Hindu revivalist Arya Samaj. Similarly, the concept of om, called onkar in Punjabi, is found in Sikh theology as a symbol of God. It invariably emphasizes God's singularity, expressed as Ek Onkar ("One Omkara" or "The Aum is One"), stating that the multiplicity of existence symbolized in the aum syllable is really founded in a singular God.
The syllable Aum is first described as all-encompassing mystical entity in the Upanishads. Today, in all Hindu art and all over India and Nepal, 'Aum' can be seen virtually everywhere, a common sign for Hinduism and its philosophy and theology.
As the creation began, the divine, all-encompassing consciousness took the form of the first and original vibration manifesting as sound "OM". Before creation began it was "Shunyakasha", the emptiness or the void. Shunyakasha is more than nothingness, because everything existed in a latent state of potentiality. The vibration of "OM" symbolizes the manifestation of God (Universe) in form. "OM" is the reflection of the absolute reality, it is said to be "Adi Anadi", without beginning or the end and embracing all that exists. The mantra "OM" is the name of God (Universe), the vibration of the Supreme. When taken letter by letter, A-U-M represents the divine energy (Shakti) united in its three elementary aspects: Bhrahma Shakti (Creation), Vishnu Shakti (Preservation) and Shiva (Liberation) Shakti.
In Hinduism, Om corresponds to the crown chakra and diamond white light. (extract from wikipedia.org)