"The Kriya Yogi endeavours to constantly remain immersed in the holy sound Pranava, the Omkara; and the deeper the concentration attained in this effort the quicker is he able to get over the attributes of senses and ultimately above the veil of Maya, Delusion."
- Sri Sailendra Bejoy Dasgupta, Kriya Yoga, Yoga Niketan, Inc.
"The type of sound that is heard by the ears after the second quarter of the night, when all is silent - ch(n)oooooooo,* through the special practice of Kriya by the Grace of Sadguru, when, being filled with inner experience, consciousness is stilled, that kind of an unearthly sound - O(N)OOOOOOOOONG** - is heard.  This is the evidence of the stilling of consciousness.  When this is sounded within, certain mudras, meaning, indications appear outside.  Seeing these, sages recognize each other.  These signs are extremely secret.  One can become aware of them through Guru."
- Swami Sri Yukteshvar Giri, Srimad Bhagavad Gita: Spiritual Commentaries by Yogiraj Lahiri Mahasay and Swami Sriyukteshvar, Yoga Niketan, Inc.
“Avagjam” - Omkar Sound flows like oil, like when pure and unadulterated oil is poured - like that - Omkar Sound is that Sound, like the sound of the long, sustaining ring of a bell - that is “avakjam” [unspoken] - that Omkar cannot be known through speech. “Pranavadya” = “pram” = that Pranava, where all merge - meaning Brahman. One who knows that is the one who is “vedavit” (is he who knows Knowing)* - meaning the par avastha of Kriya.
- Lahiri Mahasay, The Scriptural Commentaries of Yogiraj Sri Sri Shyama Charan Lahiri Mahasaya Volume 1, KRISHNA-YAJURVEDIYA-DHYANABINDU UPANISHAD Verse 18, Yoga Niketan, Inc.
Always being in the sound waves of 'Om' and by the minds fixation in it yoga or unity is achieved. Thus listen to the sound of 'Om'- always.
Excessive Pranayams steady the air within you. After sometimes doing your sadhan with great concentration, at the start you will hear a vibration of somewhat a fine net like subtance. It will not seem to be coming from far or as if it were from living being from another planet; but due to excessive pranayams that steady the vayu a sound develops which is followed by the by the sound of a bell ringing at a distance. In the beginning it will create a fluctuation in the mind, but steadying the self in it, the previous sound changes into the sound of 'aum' or 'Om' which is an existing sound and gives the Sadhak a still and steady condition of the mind and heart; deep sounds of veena, venu and conchshell are also experienced. Says the great saint poet Kabir - "rag rag bole Ramji, rera rome rara-ronkar" or your whole body says Ramji and your pores of the body sound with 'Om.' This spiritual sweet sound fills the body and mind with peaceful stillness and steadiness. All gets lost in this sound and from it appears true knowledge of the spirit of Atma.
- Sri Sanyal Mahasaya from Spiritual Gita 2:53, English translation by Smt. Chandrakanta Agarwala
When Hari puts the flute to his lips
The still are moved and the moving stilled;
Winds dies, the river Yamuna stops.
crows fall silent and the deer fall senseless;
bird and beast are stunned by his splendour.
A cow, unmoving,
dangles a grassblade from her teeth;
Even the wise can no longer
hold firm their own minds.
Surdas says: Lucky the man
who knows such joy.
- Poems to the Child-God: Structures and Strategies in the Poetry of Surdas by Kenneth E. Bryant