Consonant voicing and devoicing

In phonology, voicing (or sonorization) is a sound change where a voiceless consonant becomes voiced due to the influence of its phonological environment; shift in the opposite direction is referred to as devoicing or desonorization. Most commonly, the change is a result of sound assimilation with an adjacent sound of opposite voicing, but it can also occur word-finally or in contact with a 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). 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:

• 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,, 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:

• 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.

In other languages

Voicing assimilation

Main article: Assimilation (linguistics)

In many languages including Polish and Russian, there is anticipatory assimilation of unvoiced obstruents immediately before voiced obstruents. For example, Russian просьба 'request' is pronounced [ˈprozʲbə] (instead of *[ˈprosʲbə]) and Polish prośba 'request' is pronounced [ˈprɔʑba] (instead of *[ˈprɔɕba]). This process can cross word boundaries as well, for example Russian дочь бы [ˈdod͡ʑ bɨ] 'daughter would'. The opposite type of anticipatory assimilation happens to voiced obstruents before unvoiced ones: обсыпать [ɐˈps̪ɨpətʲ].

Final devoicing

Main article: Final-obstruent 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.

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 [ˈzaːɡn̩], Yiddish זאָגן [ˈzɔɡn̩], and Dutch zeggen [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 [ˈsɛjːa], and Icelandic segja [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).