There is a very confusing aspect of the ‘S’ sound in American English. ‘S’ has more of a light ‘Z’ sound in some common words when the ‘S’ follows a vowel.
However, there are a few exceptions, for example ‘is’; it has the ‘Z’ sound, but ‘this’ does not. The rule is this: if ‘S’ follows a vowel or a voiced consonant, it sounds like ‘Z’. Here are some of the common ‘Z’ sound words:
Notice that the words above follow sound patterns. You can do the same as you listen for this sound. If you hear it in one word, other similar words are likely to have it too.
If you use the ‘Z’ in a few common words, your awareness will build naturally and your ear will pick up on the sound when other people in your everyday life use it in other words. This sound is soft. As it comes at the end of the word, it is quite brief. The only real difference between this and a regular S is that you’re vibrating the sound a little bit.
1. Driving is difficult in a new city because interstate signs can be confusing.
draɪvɪŋ z dɪfɪkəlt ɪn ə nu ˈsɪ-tē bɪ ˈkɒz ˌɪn(t)·ərˈsteɪt saɪnz kən bi kənˈfjuːzɪŋ
because \bɪ ˈkɒz\
The letter T in interstate is silent. When T comes after N, the T sound is dropped in many words.
As in … interview –> inerview, wanted –> wanned
(I have explained this in another article: The Sounds of T in The American English Pronunciation.)
2. If you’re blocked by traffic and in the wrong lane, you can be forced to go south instead of north. Then you have to worry about turning around.
ɪf jʊr blɒkt baɪ ˈtræfɪk ənd ɪn ðə rɒŋ leɪn ju kən bi fɔːrst tə ɡəʊ saʊθ ɪnˈsted əv nɔːθ ðen ju həv tə ˈwʌri əˈbaʊt ˈtɜr.nɪŋ əˈraʊnd
instead of \ɪnˈsted əv\
3. My husband used to live in San Fransisco. He moved to Seattle and we met soon after that.
maɪ ˈhʌzbənd ˈjuːst tə lɪv ɪn san frænˈsɪskəʊ | hi muːvd tə sɪˈætl̩ ənd wi met suːn ˈæftər ðæt
4. My husband says the interstate signs in San Fransisco are much better than the signs in Seattle.
maɪ ˈhʌzbənd ˈsez ði ˌɪn(t)·ərˈsteɪt saɪnz ɪn san frænˈsɪskəʊ ə ˈmʌtʃ ˈbet̬·ər ðən ðə saɪnz ɪn sɪˈætl̩
The letter T in better sounds like the letter D. When T is between two vowel sounds (A,E,I,O,U) or between a vowel and L or R, it becomes a D sound. It should be a soft, light sound. This is the key difference between British and American speech. (I have explained this in another article: The Sounds of T in The American English Pronunciation.)