Not every sound is pronounced in English.  These are called silent letters.   A silent letter occurs in the following:

RH is pronounced as R in RHYME, RHYTHM

GH is pronounced as G in GHOST, GHETTO

MB is pronounced as M in LAMB, BOMB

WR is pronounced as R in WRITE and WRONG

GN is pronounced as N in GNAT, GNAW

KN is pronounced as N in KNIGHT, KNOW