Your kids have first grasped the idea of a sound wave using beloved slinkies as well as some physics/math equations.

What you see in this pics is the second part of our session today: guitar building! It has not been a K-2 project but a real sound wave building project.

Graham explained to me the relationship between sound waves, frequency, pitch, and hertz. He was very excited about this project and proud that he had a pretty good ear for pitch.