S (letter)
S is a hissing sound, unvoiced, like c in nîce, or voiced, a buzzing sound like z in zoô.
The UNVOICED, hissing s: sõap, stew, schême, sky, spêed, Srì Lánka (or *Shr-), mòuse, scêne, péts, píps, pāst time = pāssed gone by, míss failure = Míss girl.
The unvoiced, hissing sound is the sound of ss: glāss, grāss, pāss (cf.), híss, lóss, ósscilate, véssel, assûme, and tréspass (where the single s is also a hiss, giving rise to the error *tresspass) though not assůre, which in BrE sounds like ashŏre and in AmE *ashûre. In Missoûri the sound is, however, a buzzing s, like z, while in crêase, dêcrêase and íncrêase (nouns), decrêase, incrêase (verbs), bâsic (as from bâse) and NÁSA (surprisingly between two vowels) it is a hiss. The hissing sound is also that of st before -en and -le (the final vowel is always schwa): lísten (*líssən), fāsten (*fāssən), whístle (*whíssle), cāstle, grístle, hústle, bústle, rústle and, with no e, mústn’t (*mússənt).
Unvoiced final s after voiceless consonants: 1. Plurals: sócks, rîghts, fláps, gáps, décks, nécks, élephants, díscs. 2. Present simple tense, third person singular: hê/shê/ít, géts, êats, séts, quácks, bàrks, pícks, gríps, āsks. 3. Possessives, with apostrophe: Pête’s dóg, thê élephant’s trúnk, Jáck’s cát’s tâil (compare íts, which is a possessive without an apostrophe: the apostrophe is used for ít’s which means ít ís: ít’s lícking íts påw). 4. Looking exactly the same as number 3, contracted ís and hás: ít’s it is, ít’s nót trûe, Níck’s hêre, Rûth’s thére, Pête’s íll, thát boòk’s stûpid, her cát’s cléver.
This sound also appears with a redundant c: scêne, ósscilate, acquiésce, éffervésce, and scéptre (AmE -er).
It’s the hissing s which begins consonant clusters: scãre, askeŵ, scrêam, skì, slîght, småll, snâil, spŷ, splásh, sprêe, sqùash, Srì Lánka, stône, stróng, swéãr, skíll and asbéstos (although this can also be pronounced -zb-).
The VOICED, buzzing s is pronounced like z in zoô. It is not found at the beginning of words: z is used instead. Voiced s is found between vowels and in front of voiced consonants: lâser, resûme, mésmerise, noise, resîgn, phrâses, Présley, Bósnia, Dísney Íslām, although there is a trend to devoice the s in the last word. But in these circumstances s can also be unvoiced as in: oâsis, crîsis, aslêep, disdâin, dismántle.