How to pronunce the plural forms of nouns

In American English, the sound of "s" depends on which sound comes before it.

1. If the noun ends in an unvoiced consonant sound: /f/, /k/, /p/, /t/, /th/-(thin), pronounce "s" as /s/.

2. When it ends in a voiced consonant sound, /b/, /d/, /g/, /l/, /m/, /n/, /ng/, /r/ or with a vowel sound, /a/, /e/, /i/, /o/, /u/, pronounce "s" as /z/.

3. If it ends with /s/, /z/, /sh/, /ch/-chair, /zh/-the second "g" in garage, /dz/-(j), pronounce "s" or "-es" as /iz/.

In other words, if the noun ends with a sound other than the 5 unvoiced consonants, pronounce "s" with a /z/ (or with an /iz/ as the case may be).