http://www.speakingtree.in/public/spiritual-blogs/seekers/science-of-spirituality/silence-is-not-just-the-absence-of-external-sound
Silence from the external sound is easy achieved I can just switch of the music system or I can lock myself inside a room or even go to a solitude place. Have I achieved the silence I was looking for? No, It can happen only if the volume of rattling of the thoughts in my mind is lowered. It is not possible to stop the murmur of the thoughts, but I can lower the pace of the thoughts and minimize the flip-flop of the thoughts.
When the flip-flop of the thoughts are reduced the sound of the heartbeat (Anahata, the unstuck sound) is audible. This subtle sound is only heard when the external sound is reduced and the Mind is projecting the thoughts at a very very very slow speed. Upanishads says when one sits in the seat of silence the primordial sound of the eternity “AUM” is clearly heard. But it needs extensive practice, though the unstuck sound of the heart beat is clearly heard if one stays clam and is concentrating on the breath.
It is amazing to know how powerful and enchanting silence can be. We humans have an intimate connection with silence. Somewhere deep down beyond the layer of consciousness in the subconscious level there is our connection with the silence. This silence is the charger of the energy and in the deep sleep it is this silence which provides us the vigor to face the next day with zeal. It is unfortunate that we are unable to know it or understand its importance, maybe because we have introduced a barrier between us and silence.
We always try to avoid silence as we are so obsessed with sound that even when we are struck at the traffic signal we need the radio to be playing music we cannot do without sound. We feel left out or lonely if there is no sound. But in reality it is silence that is our best companion. It remains with us even if the external sound has ditched us. We feel heroic by defeating silence. Even at birth we announce our arrival with a shrilling noise and amazingly we continue to be noisy in our entire life span. Sound is never a hindrance there are vibrations in music. Nada yoga prefers music to elevate from the conscious level to merge with the Absolute. Just as the light is perceived well in the pitch of darkness, the silence is audible clearly if the sound is the divine music.
Lord Dakshinamurthy, the Lord of Jnana uses silence to express his views to His disciples. It is known that when our senses, mind and intellect is unable to comprehend the expressed theme the easiest channel to grasp it is silence. Even today many scientists, writers, creative professionals get the ideas when they are in seat of silence. If the teacher like Lord Dakshinamurthy communicate through silence, His disciples can grasp it silently. Silence is the most powerful way of communicating. And in spiritual word it is silence which teaches more than discourse and sermon. Discourse and sermon is like the initial push if one sits in the seat of silence and contemplate on those words of the discourse, and then the conveyed thesis is understood clearly.
Why is it important for a guru to teach in silence? It is due to the difference in the bandwidth of the students. When the Guru explains in a quite communication, it become simple to understand for the students who are loaded with different Sanskaras (impressions) and Vasanas (tendencies) due their bondage with it since past. The power of a word or the emotions behind it reflect differently to different sanskaras and vasanas, however subtle the words may be, but the realm of silence is same to all.