The Soham (pronounced "So Hum") Mantra is found in the Isha Upanishad. It literally translates to “I am that.” It is the natural vibration of the SELF. It helps you connect your SELF with the universe/ultimate reality. Thus, repeating the phrase helps to center you into a feeling of interconnectedness. According Swami Sivananda, "Meditation on Soham is same as meditation on OM. Soham is only OM. Delete the consonants S and H. You get OM."
This meditation was adapted and shortened from Yoga International's version.