Ikhfa: Means to pronounce a letter with a very light sound in the nose.There are 15 letters of Ikhfa. If any
one of them comes after a Noon Saakin or Tanween,it should be pronounced with the quality of Ikhfa.
ت ث ج د ذ ز س ش ص ض ط ظ ف ق ك
click here to listen to the Ikhfa in ths Ayah ان الانسان لفي خسر