Voice (phonetics)

In phonetics, voice or voicing is one of the three major parameters used to describe a sound, along with place of articulation and manner of articulation. It is usually treated as a binary parameter with sounds being described as either voiceless (unvoiced) or voiced, although in fact there can be degrees of voicing (see below).

A voiced sound is one in which the vocal cords vibrate, and a voiceless sound is one in which they do not. Voicing is the difference between pairs of sounds such as and  in English. If one places the fingers on the voice box (ie the location of the Adam's apple in the upper throat), one can feel a vibration when one pronounces zzzz, but not when one pronounces ssss. (For a more detailed, technical explanation, see phonation.)

Vowels are usually voiced. Consonants may be voiced or unvoiced.

Voiceless and voiced consonants
Obstruents commonly come in voiced and voiceless pairs like those above. Voiceless consonants are usually articulated more strongly than their voiced counterparts, because in voiced consonants, the airflow energy used in pronunciation is split between the laryngeal vibration and the oral articulation.

Voiceless vowels
The IPA diacritic for voicelessness is the under-ring,. This is used where no separate symbol is available, for example for voiceless vowels.

Vowels may be voiceless, usually allophonically. For example, the Japanese word sukiyaki is pronounced. This may sound like to an English speaker, but the lips can be seen compressing for the. Something very similar happens in English with words like peculiar and particular.

Voicing in English
Beside the pairs of voiceless and voiced 'obstruent' consonants given above, other voiced sounds in English are the nasals, i.e. ; the approximants, i.e. (the last spelled ); and the vowels. These sounds are called sonorants.

In most languages, the difference between and  is that  are voiced, while  are not. However, in English, the main distinction is not that are voiced, but rather that  are aspirated. That is, they differ in when voicing starts. In most English dialects, are partially voiceless in some environments, such as word initially. In fact, after an, the contrast between  and  is lost; when a child learning English has acquired voicing distinctions, but not yet acquired the clusters , the child's pronunciation of spy, sty, sky sounds to an adult like buy, die, guy.

Degrees of voicing
There are two variables to degrees of voicing: intensity (discussed under phonation), and duration (discussed under voice onset time). When a sound is described as "half voiced" or "partially voiced", it is not always clear whether that means that the voicing is weak (low intensity), or if the voicing only occurs during part of the sound (short duration). In the case of English, it is the latter.