Naad

"Naad" ( Punjabi ਨਾਦੰ ) means "the cosmic sound" or "vibrations of the cosmos". Gurbani says that: The sound of the Cosmos can resonate within if one "tunes into this energy". Only by following the rules of nature and realising the patterns and disciplines of the cosmos can one find this hidden energy of internal sound. Only through meditation, external singing and reciting can the bombardment of random noise in the mind be subdued. This internal noise that normally overwhelms the mind can be silenced and one can enjoy and hear the "anhad Naad" ("unheard sound"); this is sound of the cosmos within the mind. It is not to be confused with external vibrations - Naad is vibration within the mind.
To start these internal harmonies one needs to recite melodies with their own voice; the singing of Gurbani kirtan or mantra will invoke the internal symphonies. The Guru tells us: The external melodies resonate and "kick start" the Naad within. Also, Gurbani reminds us to: When on engages in the Lord's praises and sings in remembrance of Him, then the Naad will begin to be heard within. 
The following words in Japji Sahib Pauri 27 "vaajay naad anayk asankhaa kaytay vaavanhaaray. kaytay raag paree si-o kahee-an kaytay gaavanhaaray." which translates to: "Numerous Sound-currents vibrate simultaneously - Where are the musicians? So many melodious Ragas are sung – Where are the singers?" and also Japji Sahib Pauri 29 "bhugat gi-aan da-i-aa bhandaaran ghat ghat vaajeh naad" which means "Make wisdom your food and compassion your attendant; The Sound-current vibrates in each and every heart."
* 43 references to the word 'Naad' in the Guru Granth Sahib
==Anhad Naad, the Cosmic Symphony==
* Anhad-Naad:The Cosmic Symphony by Kailash Vajpeyi
In a world full of cacophony and chaos, it does seem a little odd to talk about ‘soundless sound’. Interestingly, soundless sound, or "anaahat", has been given equal importance in almost all systems of faith.
Chanting is articulated sound. “Aad aneel anad anahat Jug-jug eko ves” sings Guru Nanak four times in Japji, The opening hymn/prayer in Guru Granth Sahib. The concept is echoed in other cultures also.
The Bible states: “In the beginning was the word” (John 1.1). Vedic scriptures also affirm that the entire cosmic creation began with sound (Brihadrayanaka Upanishad 1.2.4.). ‘God is word’ denotes the physicality of sound but the concept of nada, that ‘God is sound’ is more subtle, because it is related to the Sanskrit word nadi, denoting our stream of consciousness. Before explaining the concept of ajapa jaap, or soundless sound, we must know about the power of the sacred word or sound.
Steven J Rosen, who wrote The Hidden Glory of India, says that a device called tonoscope, graphically demonstrates the power of classical syllables to evoke forms in a physical medium. The tonoscope is a tube suspended over a thin membrane and covered by a layer of fine dust. When sounds are broadcast through the tube, corresponding designs form in the dust that can tell us something about the initial sound that went through the tube. “While most sounds produce random ill-defined forms, the vibrations of a referable incantation produce quite a different result. If the sounds of mantras can activate a gross element such as dust, one can only imagine the power such vibrations have on human consciousness,” he says.
The power of the spoken word, especially japa, has been described in other cultures also. Saint Paul said: “Everyone who calls upon the name of the Lord will be saved” (Romans 10.15). “From the rising of the sun to its setting the name of the Lord is to be praised,” said King David (Psalms 113.3). The Buddha declared: “All who sincerely call upon my name will come to me after death and I will take them to paradise,” (Vows of Amida: Buddha 18).
"Ajapa jap" and "anhad naad" are basically related to electrophysiology. Silent chanting generates a kind of tapas, which flows in a rhythmic wave pattern. Hans Berger, a German physicist, discovered that not only all living tissues are sensitive to electric currents, but after a certain time the tissue itself generated small voltages. Today, Hans Berger's experiment has been broken up into many components by instruments that can detect fluctuations as small as one ten-millionth of a volt. It would take about 13 million of such currents to light a small flash light bulb.
The audibility of sound waves depends on their frequency and velocity. A sound wave may be audible or inaudible, depending upon the medium through which it travels. All sound is the result of some sort of striking. That is why it has a beginning and an end. But if there could be a sound which is unstruck, then it will have neither a beginning nor an end. Heard and unheard both, it will definitely be imperishable.
A perfect example of soundless sound is described by late Prof. Puran Singh in his book The Story of Rama. Puran Singh arranged a series of lectures by Swami Ram Tirth in Japan which evoked tremendous response.
Prof. Puran Singh, a bio-scientist who authored Swami Ram's biography, writes: One night after dinner when Swami Ram went to sleep, around 12.30 at night, he (Puran Singh) heard a feeble sound as though someone is saying ‘Ram….Ram….Ram.’ Puran Singh got up and opened the door – but no one was there in the corridor. After a gap of about half an hour he again heard the same sound. This time he entered the room of Swami Ram. To his utter surprise he discovered that though Swami Ram Tirth was fast asleep, the room was resounding with Ram Naam which was coming from his body rather than from his mouth.
[Courtesy:www.Spirituality.indiatimes.com]