The following is rule two of four for the Noon Al-Saakinah/Tanween.
We all know the children’s game, hide and seek. Here, the Noon Al-Saakinah must be hidden [i.e. not pronounced clearly]. Read on.
Rule Two: Ikhfaa — Al-sitr (where the Noon/Tanween is not pronounced clearly, i.e. is hidden).
The first rule listed six letters that follow the noon al-saakinah. In that case, it must be pronounced clearly. Of the remaining letters in the Arabic alphabet, the second rule, ikhfaa applies.
The letters which are covered in rules three and four, are the exception to this rule.
These letters are:
ب و م ن ي ر ل
laam raa yaa noon meem waa baa
When one of the remaining letters follows a noon saakinah or tanween, ikhfaa must be done. This is when the noon saakinah or tanween is hidden in the nose. Here, the mouth is to be shaped in a manner such that it is “prepared” for the next letter. For example, if the next letter is a taa with a dhammah then the mouth is prepared to say this by changing it into a small “o” shape, and the tongue positions itself in the right place within the mouth. This can occur across two words or be contained in one.
Ikhfaa must be sounded for two counts, i.e. the time it takes to say the words, “one – two”.
Examples of the second rule are as follow:
example one: min qabl – منْ قبلِ
example two: kitaabun kareem – كِتابٌ كريم
example three: antum – أنْتم
It is not necessary that you learn all these letters. It is however advised that you learn the 6 ith-haar, and 7 exception, letters and so when reading, just do a quick check to see if the letter is not one of the 6 ith-haar letters, or the exception letters above, then do ikhfaa. This takes a while to get used to, and soon you’ll forget you even have to do a check because you internalise it.
Besides, it’d be almost the impossible to try and bring out an “nn” sound from your nasal passage when needing to shape your mouth for a “h” sound for haa, or an “a” sound for alif.
– Sukoon [Gateway to Arabic, page 48]
– Makhaarij Al-Huroof
 – More about the Arabic letters can be found here: http://www.meem.freeuk.com/ scroll down to the “ABJAD TABLE” and select a letter.
 – Refer to the document Makhaarij Al-Huroof under the resources page.