ॐ OM ॐ The Universal Symbol of Sound. Also a mystic syllable, considered the most sacred mantra in Hinduism and Tibetan Buddhism. It appears at the beginning and end of most Sanskrit recitations, prayers, and texts.
And from a yogic perspective, there is a profound connection between speech (the expression of our thoughts) and prana (the life energy carried on the breath). When we speak, we are naming our reality, while using the power of the breath in order to form and express our words. Speech is prana in action. Prana naturally creates sound.