Nad in the ordinary sense means sound of any kind. It is created when one object touches, strikes, ruffles or hits another object.  Thunder in the sky, rustling of the wind, chirping of birds, strains of instrumental or vocal music, whirring of machines, and many other natural or man-made sounds fall in this category of physical sound.

The term Nad however has a different and special connotation in Yogic literature and practice. Nad in spiritual sense is an unstruck sound — a sound which has not been created by the friction between any objects.  It is a ceaseless sound which pervades the entire universe. According to ancient scriptures like the Vedas and the Upanishads, it is from this  Anahat (eternal / endless) sound that the entire universe came into being. In fact it is also said that Nad is the manifestation of the divine absolute itself in the form of sound, ‘Om’. It is this divine sound that connects the seeker with higher planes of consciousness.

Many Guru Siyag’s Yoga practitioners, after experiencing the Ajapa Japa (involuntary chanting) stage begin to hear a peculiar non-stop sound in one of the ears. This sound resembles any one of the limitless varieties of natural or man-made sounds. Some of the commonly experienced sounds are: chirping of crickets, buzzing of bumble-bees, notes of a flute, strumming of Veena (a stringed Indian musical instrument), pealing of bells, clash of cymbals etc. This sound that the practitioner hears is called the Anahat Nad (eternal sound). Though this Nad resembles sounds commonly heard in our physical world, it is actually a subtle version of the divine sound that the mantra given by Gurudev represents (Vaikhari Vani or the articulated word is the grossest form of divine sound energy). So the practitioner actually becomes aware of (or senses) rather than hears the Nad. As the Nad is a subtler form of Gurudev’s mantra, and it is always the seeker’s endeavor to ascend to subtler planes of consciousness, the practitioner must stop chanting once the Anahat Nad begins. Before one stops chanting, it is important to ensure that the Nad can indeed be heard ceaselessly and is not a brief experience. Listen to the sound carefully for a couple of days. If the intensity of sound grows and can be heard even in a noisy environment, then know that what you hear is the Anahat Nad.

Gurudev advises disciples to listen to this Nad intently as much as possible.  By listening to the Nad with concentration for long periods, the practitioner’s wavering mind gets attuned to the divine sound and eventually becomes one with it. During meditation, the human body acts as the medium for receiving and experiencing vibrations from subtle planes that lie far beyond our physical world. Therefore, Nad that a seeker hears in his ear is not a physical sound but a subtle sound emanating from its original divine source.

The significance of Nad can be seen in the context of Gurudev’s lucid explanation of how an individual’s spiritual evolution is directly linked to the descent of the divine into matter when the universe was created through ‘Om’, the unstruck sound. The creation of the physical universe happened through five sequential stages when Om, the divine itself, descended from Akash (sky/ ether), the highest plane, through Vayu (wind), Agni (fire) and Jal (water) onto Prithvi (earth). Each one of the five descending elements represented a grosser form of the divine than the previous one. Prithvi represents the grossest form of matter where the divine settles down and assumes myriad forms — from human to the tiniest of insects and germs.

There is a subtle element called Tanmatra behind each natural element. These Tanmatras  give us our five physical senses. Thus sky has Shabd (speech), the divine word or sound as a subtle element; wind has Sparsh (touch); fire has perception (seeing); water has Swad (taste) and earth has Gandh (smell). These physical senses tie us down to the material plane as a result of which we forget our true divine self and get mired in the illusion of joys and sorrows.

We can get out of this trap, says Gurudev, by reversing the process of divine descent into matter. When we practice the mantra-meditation, our awakened Kundalini helps us to rise in consciousness by conquering each element along with its physical sense and ultimately reach the pinnacle of spiritual evolution in Sahasrara. The Nad then is the divine sound from which we descended and it is to this divine sound we return, to our original home.