Some suffixes have two parts. Two-syllable words will have one syllable stressed with higher pitch and longer vowel duration and one syllable not stressed with shorter vowel duration and the high probability that the vowel sound will change to the "schwa" sound of "uh" /ə/. This is also what happens when suffixes have two syllables. In addition, the pronunciation of /t/ can change to /d/ when it's between two voiced sounds.