Man is distinguished from the other primates by having the apparatus to make the sounds of speech. Of course most of us learn to speak without ever knowing much about these organs, save in a vague and general sense - so that we know how a cold or sore throat alters our own performance. Language scientists have a very detailed understanding of how the human body produces the sounds of speech. Leaving to one side the vast subject of how we choose particular utterances and identify the sounds we need, we can think rather simply of how we use our lungs to breathe out air, produce vibrations in the larynx and then use our tongue, teeth and lips to modify the sounds. The diagram below shows some of the more important speech organs.
This kind of diagram helps us to understand what we observe in others but is less useful in understanding our own speech. Scientists can now place small cameras into the mouths of experimental subjects, and observe some of the physical movements that accompany speech. But most of us move our vocal organs by reflexes or a sense of the sound we want to produce, and are not likely to benefit from watching movement in the vocal fold.
The diagram is a simplified cross-section through the human head - which we could not see in reality in a living speaker, though a simulation might be instructive. But we do observe some external signs of speech sounds apart from what we hear
