Sound Waves in Physics

Sound is a pressure wave, so what the ear hears is really a squeezed and stretched column of air rather than anything moving towards you. The particles only vibrate about their own places, and the loudness you perceive is the energy those vibrations carry per second, which is why the ear responds to sound on a logarithmic scale. What makes sound especially useful is that its speed is fixed by the air rather than by the source, so a moving source or a moving listener can shift the pitch without changing the note being played. The blocks give the pressure and displacement relation, the speed in each kind of medium, the intensity and its decibel scale, and the Doppler shifts that follow from relative motion.