I've learnt that air is released from the lungs which passes through the voice box and is stopped at any point to form the makhraj of that letter...

Question
Assalamu'alaikum
Quick question: I've learnt that air is released from the lungs which passes through the voice box and is stopped at any point to form the makhraj of that letter...now looking at an image of the larynx it seems to be located above the middle of the throat. I am now confused with regards to those letters which originate below this point in aqsaa halq. How can a letter originate before the sound is produced?

Answer
Wa alaikum assalaam wa rahmatullahi wa barakatuh,
Yes, it is true that after studying the speech mechanism that it has been found that sounds are formed at the larynx in conjunction with the two components of articulation at the area for that letter.   
The throat as far as the articulation points starts from above the larynx (voice box).  So the deepest part of the throat is closest to the vocal cords, but above them, and the other articulation points of the throat are above this, meaning closer to the mouth.
Baarak Allah feekum.