Voice

Voice has two different meanings in language.

Grammar
In grammar, it is the term used to describe the relationship between verbs and the noun phrases which function as their grammatical subjects. Grammarians generally recognise two voices in English, the Active, in which the grammatical subject performs the action denoted by the verb, as in John opened the door; and the Passive, in which the grammatical subject is affected by the action of the verb, as in The door was opened (by John).

Only transitive verbs have a passive form.

There are a number of verbs used intransitively with a meaning in which the grammatical subject is not the performer of the action as such - the door opened. Some grammarians refer to these verbs as being in the Middle Voice, i.e. halfway between Active and Passive. Most writers, however, consider that such verbs (known as ergative verbs) are functioning in the Active Voice.

Phonetics
In phonetics, it refers to the sound that characterizes the articulation of a vowel or a sonant (a voiced sound that forms a syllable or syllable nucleus ) produced when the vocal cords are vibrated by the air forced through the glottis.