Letter Hamza is belongs to connecting group of letters - this letter may be connected from both side. The close similar sound in English are " in etc.
The sound of letter Alif and Hamza is identical. The Holy Qur'an printed in sub-continent Indo-Pakistan instead of printing Hamzah over Alif (where a hamzah comes in the middle of a word and is shown riding an Alif such as ) it is simply denoted by sukun sign and Hamzah is pronounced. But in the copies of the Holy Qur'an printed in Egypt, Turkey, Saudi Arabic and elsewhere a Hazah with a sukun is actually printed over Alif and this is in fact, is the correct script. example
Similar shape group
Letter Hamza is pronounced from the bottom of the throat nearest to the chest.
Letters of Aqsa-e-Halq