This question has driven the development of the 3 models, the sound wave, the middle ear and the inner ear.
We want to provide a model that can be built up and experimented with by primary school kids in small groups.
This is why the model comes in wooden laser cut (1) pieces which are easy to handle. All parts are labelled and have a part number.
This makes finding parts which belong to one of the three main parts easier. A simple but telling design by DEROBERHAMMER (2) gives an idea which physiological component is displayed in the models.
Additional graphical hints, for example, make finding the corners of the middle ear model and the order of the air molecule pendulums easier.
We modelled air molecules as pendulums. Like real air molecules, these pendulums repel each other when they get too close. Magnets in the pendulums simulate the interactions between the air molecules.
Orientation and distance of the pendulums are key. Mount the pendulums on the automatically machined (3) "bridges". The orientation of the outermost pendulums is also important. One should be pushed through the "outer ear", the other one should push the "ear drum".
The mechanical elements of the middle ear are mounted in a simple square box. The order of parts is important. The ossicles, malleus, incus, and stapes are simple levers connected by screws. Don't screw them in too tight, otherwise the middle ear will lose its primary function.
The human inner ear contains delicate structures, like this model. A string connects a series of pendulums, and each has a specific place. A key to good experimental outcomes is the tension of the string. After the pendulums are attached, it should not be too tight, nor too loose, as you will find out.