Honey, s or z 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).

it depends on the previous sound. If the previous sound is voiced (eg: a vowel sound, d, b, etc ) the plural would be /z/, which is also a voiced sound; if the previous sound is voiceless (eg: t, k, p) the plural would be /s/, which is also a voiceless sound to know if a sound is "voiced" or "voiceless" touch your throat while you are pronouncing it; if the vocal cords vibrate, it is a voiced sound, if they do not vibrate, it is a voiceless sound the plural would be /iz/ when the prevoius sound is a "sibillant" that makes it impossible to add just /s/ or /z/, which are also sibillants eg; boxes, sandwiches, roses, suitcases, garages. i hope this helps

Hi this site will explain it for you http://netgrammar.altec.org/Support/a101b3_101000.html

Easy: The voiced 's' always follows a voiced sound. The unvoiced 's' follows an unvoiced sound.

English script is not phonetic and the spellings can be quite confusing at times. There is as such no "rule" that would tell you whether the "s" is a "s" or "z" ... You can try listening to a native speaker or on television as to how individual words are pronounced. However in conversational English it is really not important to focus on just one syllable... If your sentence is correct, you would be understood correctly.