Voiced or voiceless?

A major division among speech sounds which is relevant for all languages is the dichotomy of voiced and voiceless. If you put your fingers on your ‘Adam’s apple’ or ‘voicebox’ (technically the larynx), and produce a very long [zzzzzzz], you should feel vibration; this shows that [z] is a voiced sound. On the other hand, if you make a very long [sssssss], you will not feel the same sort of activity: [s] is a voiceless sound.

Pulmonic egressive air flows through the trachea, or windpipe, and up into the larynx, which is like a mobile little box suspended at the top of the trachea, acting to control the airway to and from the lungs, with the epiglottis above it protecting the lungs by stopping foreign bodies like food from dropping in. Stretched across the larynx from front to back are the vocal folds, or vocal cords. These can be pulled back and drawn apart, in which case they leave a free space, the glottis, through which air can flow: this is the case for voiceless sounds like [s]. For voiced sounds, the vocal folds are drawn together, closing off the glottis; however, the pressure of air flowing from the lungs will cause the folds to part, and their essentially elastic nature will then force them together again. Repetitions of this cycle of opening and closing cause vibration, as for [z]. The number of cycles of opening and closing per second will depend on the size of the vocal folds, and determines the pitch of the voice: hence, children’s smaller, shorter vocal folds produce their higher voices. Although sounds can be voiced in any position in the word, voicing is most obvious medially, between other voiced sounds: when there is an adjacent voiceless sound or pause, voicing will not last for so long or be so strong. Consequently, although English has the minimal pairs tip – dip, latter – ladder, bit – bid for /t/ versus /d/, [d] is only voiced throughout its production in ladder, where it is medial and surrounded by voiced vowels. Word-initially, we are more likely to identify /t/ in tip by its aspiration, and /d/ in dip by lack of aspiration, than rely on voicing.

Voicelessness and voicing are the two main settings of phonation, or states of the glottis: for English at least, the only other relevant case, and again one which is used paralinguistically, is whisper. In whisper phonation, the vocal folds are close together but not closed; the reduced size of the glottis allows air to pass, but with some turbulence which is heard as the characteristic hiss of whisper.