1. The problem statement, all variables and given/known data What characteristics of a sound (such as frequency and wavelength) change for the speed of sound to change in each medium? Why do these characteristics change? For example: Why does the pitch of sound produced by pouring water into a tube increase as more water is poured in? 2. Relevant equations V = frequency X wavelength Physical properties of the medium: density, elastic properties, etc. 3. The attempt at a solution I understand that sound often travels fastest (out of solids, liquids and gases) in solids, less fast in liquids, and slowest in gases. I understand that the length of the tube changes the standing wave in the tube, but I ponder why the sound speed increase in the water changes the characteristics of the sound (i.e. frequency and/or wavelength). Reflection of the sound wave off of the water surface makes sense. Perhaps some of the sound enters and propagates through the water, then reflects off the bottom of the tube, and exits the water with a different frequency. Perhaps it is the cohesion between the H2O molecules to be a distance apart, where the sound wave energy diffracts around the molecules to create a larger frequency or wavelength.