"He who would hear the voice of the silence, the soundless sound, and comprehend it, he has to learn the nature of the intense and perfect concentration of the mind upon some one interior object, accompanied by a complete abstraction from everything pertaining to the external universe, or the world of the senses. Having become indifferent to objects of perception, the pupil must seek out the Raja of the senses, the thought-producer, he who awakes illusion.
The mind is the greater slayer of the Real. Let the disciple slay the slayer. For when to himself his form appears unreal, as do on waking all the forms he sees in dreams; when he has ceased to hear the many, he may discern the One - the inner sound which kills the outer.
Then only, not till then, shall he forsake the region of the false, to come into the realm of the true. Before the soul can see, the harmony within must be attained, and fleshly eyes be rendered blind to all illusion. Before the soul can hear, the image (man) has to become as deaf to roarings as to whispers, to cries of bellowing elephants as to the silvery buzzing of the golden fire fly.
And then to the inner ear will speak."
~ P.D. Ouspensky, 'Tertium Organum'