1. Speech and air. Speech is a disturbance of air pressure which a speaker brings about by moving various parts of their body. (Speech is a kind of continuously controllable human sound. All sound is just disturbances of air pressure.)
a) Take a deep breath and say "aaah!"2. Respiration. There are not really any organs of speech as such: all of them originally evolved for other purposes, e.g. lungs for breathing, vocal cords for preventing choking, tongue for eating and tasting, nose for breathing and smelling, lips for eating. In the evolution of speech, we have adapted these organs for other purposes, namely in producing communicative noises.
b) Take another deep breath, hold your breath, and, still holding your breath, say "aaah!" again. (Impossible, see!)
c) If you made a noise the second time, you were not really holding your breath (unless you have sprung a puncture).
d) As you say "aaah", feel your chest "deflating". In order to speak, it is necessary to get the air in your body moving. This can be done just be breathing out.
e) Can you say "aaah" while breathing in?
f) As you say "aaah", feel your your throat, around the area of the larynx ("Adam's apple"). Can you feel the vocal cords "buzzing".
g) Now try whispering "aaah". Do the vocal cords buzz? The vocal cords modify the flow of air coming out of your lungs, but this modification is not necessary in order for you to hear "aaah". (Whispering is audible, after all.)
h) Where does the air leave your body? Does it come out of your mouth? (Try holding your lips shut tight as you say "aaah!". Is it possible?) Try holding your nose shut? (Pinch the nostrils.) How does this affect the sound?
i) Now say "bah!" a few times. Concentrate on the "b". Is there any air-flow out of your mouth and/or nose during the time in which your lips are closed for the "b"?
j) Can you say "bah" while breathing in?
3. Egressive and ingressive. The normal direction of airflow is called egressive. Speech produced by breathing in is called ingressive.
4. Some IPA symbols. The "aaah" sound is a vowel: in phonetics, the terms "vowel" and "consonant" refer to kinds of sound, not to letters. The IPA symbol for the "aaah" sound is . Note that in the IPA, this is a distinct symbol from other "a"-like letters, such as [a]. "Baah" is written [b]. "Daah" is written [d], and "gaah" is written . Note the shape of IPA . The normal printed form of this letter, "g", is not usually used in the IPA, though it is a recognised variant of .
5. Implosives. A kind of sound like [b], [d], and  can be produced by sucking air into the mouth. Implosive [b], for instance, is made by holding the breath, closing the lips as for [b], and then sucking. (Do not purse the lips or allow your cheeks to be sucked in.) The sucking is done by closing the vocal cords together and so that the mouth cavity is competely shut off from the lungs.
As you suck in, the larynx is pulled down (feel it!), enlarging the size of the mouth cavity, without changing the amount of air in the mouth. This makes the air pressure inside the mouth lower than the air pressure outside your body. When you open your lips as for [b], the air rushes in to your lips, making an unusual ingressive sound. The ingressive forms of [b], [d] and  are called implosives. There are special letters for implosives, formed by adding a hook to the usual plosive symbols. For example, the velar implosive is transcribed . These other symbols are on the IPA chart, under "CONSONANTS (NON-PULMONIC).
i) Observe and note:
ii) Practise egressive and ingressive speech. [b],
etc. Try saying these with different vowels, e.g. [i] ("ee", as in
[u] ("oo" as in "boo!"). Observe yourself as you speak, by
in a mirror. Note what it feels like as you breathe in and out, and as
you speak using egressive and ingressive air.