pythagoras is said to have made the earliest acoustical observations when he described the arithmeticected to their mathematical and philosophical description of the universe: how the planets, the sun and the stars vibrated in harmony, creating a "music of the spheres." in the ensuing 2,000 years, we've learned that this connection between math and music, whether mystical or not, is all about waves. sound is simply a disturbance of air, as pythagoras observed, a vibration, but as we now understand, a vibration that extends through space in the form of a wave. the initial disturbance can be caused by anything, and that anything is called an oscillator, like a vibrating string. but like ripples on a pond, the sound wave spreads when molecules in the air are disturbed and themselves begin to vibrate. the vibrating air molecules, in turn, bump into other nearby molecules, causing air pressure to compress and expand. this changing air pressure creates alternating waves that extend from the source of vibration. if a person is in the path of the sound wave and then the wave enters the ear, i