Certain pairs of consonants are difficult to pronounce for speakers of some languages. These charts put together some of the difficult pairs or groups.
L and R [ l ] and [ r ]
Nasals [ m ] [ n ] and [ ng ]
Stops [ t ] and [ d ] [ k ] and [ g ]
Labials
[ p ] and [ b ] [ w ] and [ v ] [ f ] and [ v ]
[ p ] and [ f ] [ b ] and [ v ] [ f ] and [ h ]
Fricatives and Affricates
[ s ] and [ z ] [ s ] and [ sh ] [ sh ] and [ ch ]
[ j ] and [ z ] [ ch ] and [ j ] [ s ] [ z ] [ sh ] [ ch ] and [ j ]
Pairs with th-
[ th ] voiced and voiceless [ th ] and [ s ] [ th ] and [ sh ]
[ th ] and [ t ] [ th ] and [ f ] [ th ] and [ z ] [ th ] and [ d ]
[ th ] and [ v ] [ th ] [ z ] [ d ] and [ v ] [ th ] [ s ] [ sh ] [ f ] and [ t ]