As a general rule, the letters having no sign on them (empty letters) must be treated as silent letters. Since they do not produce any sound of their own therefore, they should be overlooked.
These silent letters generally occur when long vowel letters (Madd) Alif, Waw and Ya are involved.
Exception to the silent letter rule is Maddah Alif refer to lesson 8.
[Special rule for letter Hamza or Alif]
When there is a letter Hamza or (Alif) with sukoon, it should be pronounced clearly and sharply.
When a vowel sign appears over or under the letter Alif , it is in fact letter Hamza.
In the copies of Middle Eastern print of Holy Quran, the letter Hamza is shown as a tiny Hamza riding over or under the letter Alif.