What’s the difference between /s/ and /z/? They are both made with the lips/tongue/jaw in the same position…
1. Put your hand on your larynx (voice box). 2. Pronounce a long /s/ sound 3. Pronounce a long /z/ sound 4. Answer the following questions:
Does the larynx vibrate?
Yes Voiced No Voiceless You’ll find that /s/ is voiceless and /z/ is voiced.
Another difference between these sounds is that /s/ is made with more air (=greater breath force) and more muscular effort. A word that describes more air and effort is fortis /ˈfɔːtɪs/. All voiceless sounds in English are fortis. All potentially voiced sounds in English are lenis /ˈliːnɪs/, which means there is less air and effort.