Consonant voicing and devoicing

In phonology, voicing (or sonorization) and devoicing are sound changes, whereby a consonant changes its type of voicing from voiceless to voiced, or vice versa, due to the influence of its phonological environment. Most commonly, the change is caused because of sound assimilation with an adjacent sound of opposite voicing, but it can also occur word-finally or in contact with specific vowel.

For example, English suffix -s is pronounced [s] when it follows a voiceless phoneme (cats), and [z] when it follows a voiced phoneme (dogs).^[1] This type of assimilation is called progressive, where the second consonant assimilates to the first; regressive assimilation goes in the opposite direction, as can be seen in have to [hæftə].

English

English no longer has a productive process of voicing stem-final fricatives when forming noun-verb pairs or plural nouns.

belief - believe
life - live
proof - prove
strife - strive
thief - thieve
ba[θ] - ba[ð]e
brea[θ] - brea[ð]e
mou[θ] (n.) - mou[ð] (vb.)
shea[θ] - shea[ð]e
wrea[θ] - wrea[ð]e
hou[s]e (n.) - hou[z]e (vb.)
u[s]e (n.) - u[z]e (vb.)

Synchronically, the assimilation at morpheme boundaries is still productive, such as in:^[2]

cat + s > cats
dog + s > do[ɡz]
miss + ed > mi[st]
whizz + ed > whi[zd]

The voicing alternation found in plural formation is losing ground in the modern language,^{[citation needed]}, and of the alternations listed below many speakers retain only the [f-v] pattern, which is supported by the orthography. This voicing is a relic of Old English, the unvoiced consonants between voiced vowels were 'colored' with voicing. As the language became more analytic and less inflectional, final vowels/syllables stopped being pronounced. For example, modern knives is a one syllable word instead of a two syllable word, with the vowel 'e' not being pronounced. However, the voicing alternation between [f] and [v] still occurs.

knife - knives
leaf - leaves
wife - wives
wolf - wolves

The following mutations are optional^{[citation needed]}:

ba[θ] - ba[ð]s
mou[θ] - mou[ð]s
oa[θ] - oa[ð]s
pa[θ] - pa[ð]s
you[θ] - you[ð]s
hou[s]e - hou[z]es

Sonorants (/l r w j/) following aspirated fortis plosives (that is, /p t k/ in the onsets of stressed syllables unless preceded by /s/) are devoiced such as in please, crack, twin, and pewter.^[3]

Initial voicing

Initial voicing is a process of historical sound change where voiceless consonants become voiced at the beginning of a word. For example, modern German [sagen] Error: {{Lang}}: text has italic markup (help) [ˈzaːɡn̩], Yiddish זאָגן [ˈzɔɡn̩], and Dutch [zeggen] Error: {{Lang}}: text has italic markup (help) [ˈzɛɣə] (all "say") all begin with [z], which derives from [s] in an earlier stage of Germanic, as still attested in English say, Swedish [säga] Error: {{Lang}}: text has italic markup (help) [ˈsɛːja], and Icelandic [segja] Error: {{Lang}}: text has italic markup (help) [ˈseiːja]. Some English dialects were affected by this as well, but it is rare in Modern English. One example is fox (with the original consonant) compared to vixen (with a voiced consonant).

Final devoicing

Final devoicing is a systematic phonological process occurring in languages such as German, Dutch, Polish, and Russian, among others. In these languages, voiced obstruents in the syllable coda or at the end of a word become voiceless.

Bibliography

Roach, Peter (2004), "British English: Received Pronunciation", Journal of the International Phonetic Association, 34 (2): 239–245, doi:10.1017/S0025100304001768
Grijzenhout, Janet (2000), Voicing and devoicing in English, German, and Dutch; evidence for domain-specific identity constraints (PDF)

[1] Grijzenhout (2000:3)

[2] Grijzenhout (2000:9)

[3] Roach (2004:240)

[1]

[2]

[3]