As I was listening to Kristen sing in the car, I was thinking about the physics in her making the noise and me hearing it. As she was creating this noise, the sound waves had to travel through a medium, being air molecules. As the wave moved through the air it vibrated them, creating the noise. As this happened, the air molecules hit my ears. I could also figure out how long it would take for me to hear Kristen singing by using velocity=distance/time. Velocity for the speed of sound is 331 m/s and I would have to measure the distance in between me and Kristen. Say the distance was 1.5 meters. This would mean that I would hear the sound .0045 seconds after Kristen produced the sound!