As they vibrated, the cords produced sound waves in the air. If you drop a pebble in a pond, it creates a circular wave that ripples through the water. The motion of Junior's vocal cords set up an alternating pattern of compression and expansion in the surrounding air. After being kicked by the cords, the moving molecules of air kicked neighboring molecules into motion, so that the pattern of movement was communicated through the air, domino-style. This pattern of movement was the sound wave.
Frequency affects the pitch of a sound.
As Junior spoke, muscles in his throat contracted or relaxed to change the tension in his vocal cords, which changed their rate of vibration, which changed the pitch of his voice. At the same time, Junior changed the shape of his throat and mouth to form the sounds we call words. To transmit and recreate the sound waves Junior produced, the telephone system used a series of transducers, devices which convert one type of signal into another. On its way from Georgia to San Francisco, the sound of Junior's voice took the form of electric current, light waves, and radio waves. All these signals traveled at fantastic speed, moving through wires, optical fibers, and air.