There are two passages leading from the oral cavity--one for food (Esophagus) and one for air (Trachea).
"Donald Duck" talk is very limited in its range of pitch and loudness, and constricts the tongue in its production.
Ironically, our generator, which is very effective and efficient comes to us perhaps through serendipity as a side effect of natures attempt to solve a serious structural problem.
Visualize this. Here we have the oral cavity which is used for two purposes: Food intake and Air Intake.
The structural problem is this."They" placed our air intake tube (the trachea) in front of the foot intake tube (the esophagus). That means that every time you take a bite to eat, you must pass the food over the trachea.
Should a tiny morsel (like a sliced carrot or even a vitamin pill) fall into the trachea, we may have just five more minutes to live--and not a particularly fun five minutes either!
NOTES: Hear Donald Duck talk.