The sacred sound of Om or God as sound, ether, space or Shabda Brahma, can be heard continuously in the silence of the day or night. It is the sacred universal sound for those who enjoy listening daily to the creative sound of the universe. This universal sound can be heard by holding the left handed conch shell close to your ears, by a single strike of the temple bell on entering the temple, and a simple rub on the Buddhist begging bowl. It is the sound we hear in our mystical experiences that take us into eternity of time and space to remind us of our oneness in time and space.
"Of all the syllables, the most powerful and the most significant one is the single syllable called the Pranava, the 'AUM', or Omkara, pronounced as 'Om'. Omkara is the holiest Vedic sound in the Hindu tradition, explaining various religious and spiritual ideas. The syllable has sound, meaning, application and efficiency. It is the apt symbol of the Supreme. The formless Lord Siva assumes the form to dance and becomes Lord Nataraja. Lord Nataraja holds in his upper right hand a small drum (damaru), which is shaped like the hour-glass, denoting the connection between sound and eternal time. He beats the drum when the primordial sound, Pranava (Om), is produced. This sound fills the universe and modifies matter and space. The evolution of the subtle as well as the gross universe, with all its entities, takes place. Further, all that is past, present and future and any thing beyond them is, verily, the manifestation of Pranava as Time, as stated in Mandukya Upanishad … To every mantra, Om, the Pranava, is added. And without Om, no sacred chant has its power. By the addition of the Pranava to any mantra, a life-giving breath flows through it."
The holy voice of God binds all religions, people, time and palce together, no matter what modifications are made to differentiate one from the other. It is the same universal sound known in almost all religions of the world. It is the same sound of Om of Hinduism, Zorastranism, Jainism, Buddhism, Sikhism and the modified sound as ShalOm in Judaism, the Amen in Christianity and the Amin in Islam. It is our reminder of the universal oneness of all and our connection and oneness with the divine when we seem to forget our unity in diversity.
The late Swami Rama chatted with Indian, Muslim Maulanas about that holy sound, Om, while he was in Luknow, India, and explained the significance of OM as referenced in their Quran and explained in the link below.
Swami Rama happened to be in Lucknow in 1905 when some Muslim Maulanas came to him to get enlightened on Hinduism and their own religion. What follows is a segment of Swami Rama's dialogue with them.
On their arrival they did Adabarz to which God-intoxicated Rama replied by Om. They wanted to know the meaning of Om. The truth was (he said) that a person can give to others only what he possesses and that Rama himself only possessed OM and that alone. That OM, which was Rama's sole possession, represented the non-duality of Vedanta. By pronouncing it properly the heart and mind are filled with peace, tranquility and bliss. You can feel the limitless ocean of power and energy within you. Rama then invited the Muslims to join him in chanting ‘om' three times, which they did and felt instant peace. Swami Rama went on to expound the special place of OM as a universal name of God, but the Muslims objected that they had never seen any mention of OM in their own holy scriptures and asked him (if what he said was true) whether he could quote any reference to OM in their Koran.
Rama replied gently: ‘Please listen to what is now being said. In the very beginning of your Koran, at the top, are three letters, alif (A), lam (L) and mim (M). Can any of you or any learned Mulawi of Islam explain what these three letters mean?' The Moslems replied that this was a secret which Allah had kept to himself. Swami Rama laughed heartily at this remark and said: ‘When God has revealed the entire Koran for the benefit of mankind, as the Muslims claim, it is very strange that he has kept its very heading a secret. No. It is not so. If you, the Muslims who put full faith in the Koran do not know the secret of the letters A, L, M, Rama will tell you what they signify. Alif, lam and mim are nothing but alif (A), wao (O) and mim (M), that is, AOM or OM.'
The Muslims objected that the letter L is not the same as the letter O, but Swami Rama pointed out to them that in Arabic grammar L is pronounced O when it falls between a vowel and a consonant, as in the names Shamsuddin, which is written Shamsaldin, or Nizamuddin, which is written Nizamaldin. The letter lam (L) becomes silent and gives the sound of the Arabic letter pesh (O or U). Therefore ALM is no secret; it is clearly and unambiguously OM and nothing but OM. It is Kufra, heretical or a sin, to blame God for keeping it a secret.