Three groups of organs assume the essential functions in the act of speech:
# The respiratory system (diaphragm, lungs, trachea), which provides the energy and the amount of air needed,
#The larynx, vibrating organ, where the sound is born,
#The vocal tract, formed of the supra-laryngeal resonant cavities(pharynx, mouth, nose) where the articulation itself takes place by the changes in shape of the vocal tract.
These changes result chiefly from the movements of the lips, the tongue, the veilof the palate(the lowering of which involves an additional cavity, the nasal fossae) and the lower jaw.
"Al Jawf" corresponds to the void inside the mouth and the throat, allowing the production of the letters
أ Alif which sounds like the sound (a), as in the word "Bad" or "Dad" in english,
و Wa that sounds (u) as in the word "clue" or in the word "cool" in English,
And finally ي Ya, which corresponds to the sound (i) of the word "pretty" in english,
Or the sound "ii" of the word "free" in English.
The major characteristic of the "vowels" produced by the human phonation apparats is the free passage of air from the supraglottic cavities.
The only treatment that air can undergo is the resonance, ie the strengthening of certain frequency bands.
The timbre of a "vowel" will depend on the variation of the following elements:
#The number of resonators put in resonance(buccal, labial and nasal);
#The shape of the buccal resonator;
#The volume of the buccal resonator.
The oral cavity, or buccal cavity, is the most important part of the vocal tract because its shape and size can vary by adjusting the relative positions of the palate, of the tongue, the lips and the teeth.
The "sound" difference between the sound "u", "ii", and "a" depend on:
#In the aperture or opening of the vocal tract, which depends on the elevation of the tongue in relation to the palatal arch( closed or open vowels);
The articulation zone determined by the position of the tongue in the buccal cavity(anterioror posterior vowels);
#The shape of the lips (vowels rounded or not rounded).
The articulation of the sound "u" is done with the back of the tongue raised and in a posterior projection towards the palate.
The veil of the patate is raised
The sound comes out exclusively through the mouth.
The jaws drew very close together and the lips are rounded is a so-called "labialized" letter.
The sound "a" is produced by the friction of the exhaled air and the participation of the vocal cords.
Mouth slightly open; The tongue is paused in its case: the oral cavity is flat.
The sound "a", that is to say the letter Alif ا in Arabic circulates freely from the bottom of the larynx passing in résonance in the void created between the tongue and the palate.
As for musical instruments, the body has its own soundbord!
Thus, by flattening the tongue a little more, a larger space is created in the oral cavity, producing a more deeper sound.
The production of the sound "ii" as in the word "we" in english is done with the veil of the palate raised, the sound exits only through the mouth.
The back of the raised tongue is projected towards the front of the palatereducing the vocal tract in its anterior part.
The jaws very close together, the lips are spread, we speak here of a not rounded sound.