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