Reflection
http://physics.bu.edu/~duffy/HTML5/reflection_transmission.html
Reflecting waves and phase change
http://www.thephysicsaviary.com/Physics/Programs/Labs/ReflectingWaves/index.html
Interference
Interference
Interference
Interference
Interference
Move microphones to find standing waves
http://www.thephysicsaviary.com/Physics/Programs/Labs/DistanceToDestruction/index.html