https://www.physicsclassroom.com/Class/sound/U11L1a.cfm
A sound wave is a mechanical wave that propagates along or through a medium by particle-to-particle interaction. As a mechanical wave, sound requires a medium...
physics tutorialmechanical wavesound
https://www.instructables.com/Cardboard-Mechanical-Wave-Toy/
Cardboard Mechanical Wave Toy: Here is a quick and easy toy that you can make in an evening. It's a great way to help children (and adults!) practice spatial...
mechanical wavecardboardtoystepspictures