The essence of Sound is vibration.
Vibration is shaped by material and geometry.
Begin with examples of geometry.
A single string.
A column of air.
The Child's voice.
Then vary the materials.
The Hand Flute is the same plastic tube used as a Static Tube with the simple addition of a hole drilled about an inch from one end. The purpose of the hand flute is to demonstrate the sound produced by the vibration of a column of air and the possibility of changing the pitch of the note produced by covering and uncovering a single hole. This is done by gripping the tube so to cover the hole with your thumb and then tapping the end of the tube with your other hand.
is a device that reveals the wave patterns that Sound produces in water. These are related to Chladni Patterns which are waves produced in powders on vibrating rigid surfaces. The Cymatic examples above were produced with an Ipad app which is one of a number of valid uses of a touch screen tablet in a primary classroom. A physical Cymascope is expensive and also necessarily removes the primary child from the circuit. So A Child's Physics will approach this concept through the use of a Singing Bowl.
The video shows the initial presentation which is just to get two notes out of the flute. Then there is a rhythmic extension. Simple as it is, this is a challenging piece of equipment for a primary child. The classroom rational behind the idea of a hand flute is that it produces a pleasing sound somewhat like dripping water but its quiet. The child doesn't blow into it or put it in her mouth on it. While a hand flute is certainly capable of multiple holes and Precise tuning that can happen later. All you need to do to put one in a classroom is cut a tube and drill a hole in it. I prefer flexible polyethylene for shorter tubes and rigid PVC for bass tubes. Below are a few sound file of different size tubes. Should the idea of using a simple plastic tube as a musical instrument seem odd or simplistic I recommend checking out steel drums.