In layman's terms: in Tehrani Persian, there is no difference in pronunciation between qaaf and ghayn; they are treated as exactly the same sound, just as siin and Saad. However, the pronunciation of that sound may differ depending on where it occurs in the word (for some speakers). Generally it sounds like what you hear in the links in post #26 above, but when it occurs in between two vowels (as in آقا or فغان) it may change to a sound something like the French 'R' which you can hear in the links in post #13.^ Lady and Getleman, if a consensus has been reached between the two of you, is it possible to have a conclusion in lay person's language which all mortals can understand? It would be even more helpful if any sound files could be attached which contrast the real Arabic qaaf and Ghain with the Tehrani qaaf and Ghain. For example how would a Tehrani Persian speaker pronounce the following words:
qariib (near) /Ghariib (stranger)
Do the q/Gh sounds change depending on the their position in a word (intial, medial or final) and/or do they change depending on the proceding/following vowel or consonant?
You can then compare these sounds with the Arabic qaaf (ie. here) which, to avoid technical vocabulary, differs from the sound found in Persian in that one's vocal cords do not vibrate while producing this sound, whereas the vocal cords do vibrate when producing the Persian qaaf. (The result is that the Arabic sounds 'harder' to my ears). The Arabic ghayn is also different, as you can hear here. It is pronounced with the tongue further forward in the mouth than the Persian equivalent: for the Arabic sound the tongue is against the back of the roof of the mouth, where kaaf and gaaf and Khaa are also produced, whereas for the Persian sound(s) the tongue is further back, against the uvula.
Hopefully that make all of this more or less clear without resorting to linguistics jargon. (Sarkaar khaanuum sapnachaandni, shomaa ham baa towziih-e iin jaaneb movaafeqiin?)