The chamber of each plastic model is shaped
like your vocal tract - the cavity formed by your mouth and
throat when you speak. Each time you say a different vowel,
you change the shape of your vocal tract. That's why each model
is a little different from the others. The plastic chambers
pictures are aligned similar to your vocal tract with the vocal
chords (duck call) at the bottom and the lips at the top.
At this exhibit, a puff of air from a bellows
makes the duck call reed at the end of a hose vibrate, just
as the air from your lungs makes your vocal cords vibrate. Like
your vocal cords, the vibrating reed produces a complex sound
composed of many different pitches.
Like your vocal tract, the plastic models
shape these complex sounds into particular vowel sounds. When
a complex sound echoes from the walls of the plastic cavity,
some pitches are reinforced and some are not. It is the reinforcement
and cancellation of certain pitches that changes the squawk
of the duck call into a recognizable vowel sound.
Here's a bonus sound from the exhibit!