| VOCAL VOWELS includes
plastic models of five different shapes that mimic the shape of
the human vocal tract making the sounds of ee, eh, oh, oo and ah.
A bellows pushes air by the reed of a duck call, making a quacking
sound. Like the vocal cords, the reed produces a complex sound made
up of many different frequencies. When the reed is placed at the
end of one of the plastic models, only some of the frequencies resonate
within the model's cavity, producing the distinctive sound.