But we make informed guesses on the evidence of speech errors, brain scanning, and effect due to brain damage.
Stage 3: Articulatory aspect of speech production
Many special instruments have been developed and they help us to find about such things as the pressure of air in the lungs and the vocal tract, the flow of air out of mouth and nose, the opening and closing of the vocal folds and the soft palate, and the movement of articulators lips and lower jaws.
Although most of these techniques are expensive and difficult to use but may become easily available.
Stage 3: transmission of sound waves through air
This stage is studied by acoustic analysis.
Physical events that produce the perceptual characteristics of speech sounds have been discovered including the duration or length of sounds or syllables, intensity of different sounds and the fundamental frequency of sounds.
Developments in the field of computer technology has made possible speech analysis on a large scale.
Additional pronunciation training is also provided by the computers.