The Expressive Transducer, and What Babies Hear
In Mysak's model, we described the Expressive Transducer in three parts: the Motor, the Generator and the Modulators.
Motor: This refers to the source of energy for speech, and if anything is going to happen muscles must be involved. Nowhere is this more true than for the speech act.
The first muscle we may all think of is the diaphragm. Actually, this is a domed shaped muscle when relaxed.
It separates the chest cavity from the abdominal cavity. When it is tensed, it flattens out, creating a partial vacuum in the chest cavity. Air will rush in through the nose, trachea ("wind pipe") and lungs to fill the space.
This is inhalation and as you can see it is an active process. There are many more muscles involved, however, in inhalation than just the diaphragm.