VOICING (LEVEL OF VIBRATION)
All of us inhale oxygen and exhale carbon dioxide. Pulmonary air gets out the lungs and enters the bronchi. The two bronchi meet each other and form the trachea. The trachea is intercepted by the voicebox or larynx on its way out. Inside the voice box, there are two membranes that are hinged together at the back. These membranes are called the vocal cords or the vocal folds. The vocal cords can make a wedge-shaped opening when they are far apart. This opening is called the glottis.
The level of vibration of the vocal cords determines whether a sound is voiced or unvoiced. When the glottis is open, pulmonary air passes through it easily without causing any friction. That is, if the vocal cords are apart, then air can escape unimpeded. Sounds produced in this way are said to be voiceless. The easiest example of this is to whisper. When you whisper, your glottis is wide open and, therefore, all the sounds produced are voiceless. However, when the glottis is closed, the vocal cords are set into vibration by the impact of the pulmonary air. When the vocal cords vibrate, voice sounds are produced. When they do not vibrate, voiceless sounds result. That is, if the vocal cords are very close together, the air will blow them apart as it forces its way through. This makes the cords vibrate, producing a voiced sound. Vocal cord vibration is technically referred to as voicing. In English, only a limited number of consonants are voiceless. /ʧ/, /s/, /p/, /k/, /f/, /ʃ/, /t/, /θ/, and /h/ are voiceless. All other phonemes are voiced.
To feel the distinction between voiced and voiceless sounds is very easy. Place your finger and thumb lightly on your throat. Say ssssssss to yourself. Then say zzzzzzz. Repeat these a few times. Then substitute fffffff and vvvvvvv sounds. You should be able to feel the vibration of the cords when you say zzzzzz and vvvvvv, but not when you say sssssss and fffffff. It is also possible to hear the vibration through bone conduction. Instead of putting your fingers on your throat, put your index fingers in your ears and repeat the above sounds. You should hear a low buzzing sound when you articulate zzzzzz and vvvvvv, but hear almost nothing for the other two sounds.
Voicing is important in a language like English because the meaning of a sound often depends on whether that sound is voiced or not. For example, 'big' carries a very different meaning from 'pig'. English has many sounds that are paired up in this way. In fact, there are a number of cases in which the place and manner of articulation of phonemes are the same, but the meaning is dependant upon whether the sound is voiced or not.
