Voice or voicing is a term used in phonetics and phonology to characterize speech sounds, with sounds described as either voiceless (unvoiced) or voiced. The term, however, is used to refer to two separate concepts. Voicing can refer to the articulatory process in which the vocal cords vibrate. This is its primary use in phonetics to describe phones, which are particular speech sounds. It can also refer to a classification of speech sounds that tend to be associated with vocal cord vibration but need not actually be voiced at the articulatory level. This is the term's primary use in phonology when describing phonemes, or in phonetics when describing phones.

At the articulatory level, a voiced sound is one in which the vocal cords vibrate, and a voiceless sound is one in which they do not. For example, voicing accounts for the difference between the pair of sounds associated with the English letters "s" and "z". The two sounds are transcribed as [s] and [z] to distinguish them from the English letters, which have several possible pronunciations depending on context. If one places the fingers on the voice box (i.e. 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 modal voice and phonation.) In most European languages, with a notable exception being Icelandic, vowels and other sonorants (consonants such as m, n, l, and r) are modally voiced.

The human voice consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc. Its frequency ranges from about 60 to 7000 Hz. The human voice is specifically that part of human sound production in which the vocal folds (vocal cords) are the primary sound source. Generally speaking, the mechanism for generating the human voice can be subdivided into three parts; the lungs, the vocal folds within the larynx, and the articulators. The lung (the pump) must produce adequate airflow and air pressure to vibrate vocal folds (this air pressure is the fuel of the voice). The vocal folds (vocal cords) are a vibrating valve that chops up the airflow from the lungs into audible pulses that form the laryngeal sound source. The muscles of the larynx adjust the length and tension of the vocal folds to ‘fine tune’ pitch and tone. The articulators (the parts of the vocal tract above the larynx consisting of tongue, palate, cheek, lips, etc.) articulate and filter the sound emanating from the larynx and to some degree can interact with the laryngeal airflow to strengthen it or weaken it as a sound source.