Technically, sound begins with the vibration of an object, transmitted to our ears by a medium, which is usually air. Our eardrums start vibrating, and impulses, or signals, are transmitted to the brain. There, the impulses are selected, organized, and interpreted.
Sound is information about our environment. The footsteps of a familiar person, the snoring by him, the voice of her, the muted typing sounds on the keyboard, the relentless spinning of the fan and the silence of us not speaking. They are neutral to others and subjective to you and i. Being omnipresent, taken for granted. The silence is loud.