The Himalayan masters of ancient India developed the 'sound current', that is now known as the 'divine sound'. The divine sound is the foundation used for practicing various forms of yoga-nada, sahaj, Babaji, kriya, and Sikh practices such as shabda yoga.
The sound current used in meditation is similar to the electric current in everyday life. When electricity runs through a power line, it creates a humming sound. Just like electricity, when spiritual energy runs through the human body, we can hear within our heads the two energy fields interconnecting―the energy of the body's physical circuitry and the current of spiritual energy.
meditation
All of creation is a manifestation of sound, known as the eternal 'om'. This sound can be heard and felt throughout our bodies, if we listen and attune ourselves to hear it. The sound experienced at first may be very subtly, so subtle that it is almost subliminal, so one must meditate quietly to be able to discern it from outer distractions in everyday life.
As you begin to meditate regularly, and as you attain deeper states of meditation, the 'om' sound can become so loud and intense that it drowns out everything else with its vibration and energy.

The current of sound experienced in Vipassana meditation is different for each person, depending on their degree of inner attunement. It may be perceived as a buzzing or ringing, a clear ringing tone, a loud roar, or the peaceful sound of waves rippling along the shore. However, it manifests itself. As you begin to pay close attention, it becomes stronger and more distinct, until it eventually merges with the basic primordial sound all of nature―the 'music of the spheres'. The sound current is very sweet and subtle. In the beginning, it will help find a place to meditate, where you can be absolutely quiet with no distractions.

After practicing for a while, you will begin to notice that the pitch of the sound changes as your brain wave rhythms change. When you are outside, soaking in the energy of the sounds and colors around you, the sound current changes as you come in contact with various natural energies and elements, resulting in a deeper level of communication with the world around you as you match frequencies with various energies. By the same token, the state of cellular health in your body is connected to the frequency with which your inner energy vibrates. Pay attention to the sound current in order to communicate with your cells, and they will begin to communicate with you.
As you begin to experience sensations in the world for what they are, you will experience the relaxing and loosening of karmic knots that you have carried in your consciousness for a lifetime. As you practice Vipassana and become more attuned to the sound flowing back and forth through your body, from your head to your feet and back again, you will begin to attain a state of equanimity that will bring you to the highest realm of spiritual experience.
buddha
The practice of Vipassana was taught by ancient Buddhists as a way to experience full body enlightenment through the awareness of sensations. The Buddha taught that the sensations experienced by the body are the doorway to the deepest levels of enlightenment. By practicing being attuned to your body, as you become more aware of the energy of your spirit, the vibrational resonance of your energy will change.
After a while, you will discover that what you had previously experienced as just an ordinary feeling of living, is becoming a vibrant, blissful, multifaceted current of being alive.