Om meditation is known to have transcendental qualities. It can bring peace and balance to the mediator's system, and is known to relieve people from numerous physical and mental ailments when practiced regularly. Inner Sounds are dormant. One has to meditate with love, devotion, recitation of the Name and meditation. That Sound is unceasing and unfathomable, and is full of bliss. Chanting of OM Mantra purifies the environment around the chanter and produces positive vibrations.
30 minute meditation
Before Lord manifested the universe, there was only oneness or perfect stillness. With manifestation, the un-moving Presence “moved” or vibrated and this movement or vibration is called Om. From OM - the Consciousness which represents the presence of God within all creation. Chant a-ā-u-ū-m ) with open mouth wide as if you want to take in the fullness of the universe. Place the tip of your tongue on the roof your mouth to sound the 'm'. After 5 second silence, chant again again. Chanting Om consistently and silently meditating for longer hours leads to Anhat-Nada.
From ancient times, Nadanusandhana was the ultimate goal of all the other yoga practices. Nāda mean 'sound', but in this caseit is Anāhata Nāda, unstruck sound. Anahat Nada is experienced by many that practice yoga. This unstruck sound or Astral Sound is not heard in the ears, but within the mind, as this sound is awakened within by the yogic practices. Anahat-Naad further progress on the path to enlightenment.
Hansa-Upanishad (written 100 BCE) says - The Nada can be heard as sound of bell; or that of conch; or that of flute; or the of drums; or that of thunder
Many yogis recommends to listen to the nada in the interior of right ear. With constant practice, the nada will become subtler and subtler.