From Lungs to Mouth
Speech sounds spellbound!
Step By Step
piece of PVC pipe 6 3/4 in (17 cm) in length and inner diameter of roughly 1 1/4 in (3 cm)
piece of rigid wire 1.5 ft (about 45 cm) in length
cork with a diameter smaller than the internal diameter of the PVC pipe
Get one end of the rigid wire stuck into the cork (this represents your tongue). Fasten the bottleneck to one end of the PVC pipe. (You may have to make several cuts in the bottleneck perpendicular to its edge to fasten it more easily to the PVC pipe, using masking tape.) Fill the balloon with air and twist its neck so that air doesn't escape. Now, ask someone to insert the "tongue" into the PVC pipe (your "vocal tract") and slip the mouth of a balloon over the bottle top. Untwist the balloon's neck and stretch it to produce sounds while the tongue is displaced along the PVC pipe. Can you notice different sounds as the tongue is displaced? If you assign to the stretched neck the role of your vocal folds and to the filled balloon the role of your lungs, then you will be prepared to follow how vowels are produced.
A Step Further
Try different PVC pipes with different lengths (vocal tracts with different lengths) and corks (tongues) with various sizes, and stretch the balloon's neck in different ways. Now, how about using a corrugated hose as a vocal tract? Can you make your model sing?
As you stretch the balloon's neck, you produce sound (see step 3 of previous experiment and the corresponding Fun Facts). In this model, the filled balloon corresponds to your lungs. The air flow through the glottis (the space between the vocal folds, represented by the stretched necks) is modulated by the movement of the vocal folds, producing a modulated air pressure. The sounds thus produced are shaped into the various sounds of speech in the mouth cavity, where they are selectively amplified as you move, for example, your tongue (represented by the cork), lips, and jaw. As you displace the rigid wire stuck to the cork in and out, you simulate some of these possibilities. Explore them all.