In linguistics, sounds can be classified as voiced or unvoiced based on whether or not the vocal cords vibrate during their production.
Voiced sounds are produced when the vocal cords vibrate, causing a buzzing or humming sound to be produced in the vocal tract. This vibration can be felt by placing one's fingers on the throat while producing a voiced sound such as /z/ or /v/. Examples of voiced sounds in English include /b/, /d/, /g/, /z/, /v/, and /w/.
Unvoiced sounds, on the other hand, are produced when the vocal cords are held apart and do not vibrate. This results in a sound that is produced entirely by the movement of air through the vocal tract. Examples of unvoiced sounds in English include /p/, /t/, /k/, /s/, /f/, and /h/.
Many sounds in English occur in pairs that differ only in whether they are voiced or unvoiced. For example, the sounds /b/ and /p/ are both produced by closing the lips and then releasing a burst of air. The only difference between the two sounds is that /b/ is voiced, while /p/ is unvoiced.
The distinction between voiced and unvoiced sounds is important in many languages, as it can affect the meaning of a word or the way in which it is pronounced. In some languages, such as Mandarin Chinese, the distinction between voiced and unvoiced sounds is crucial for distinguishing between words with different meanings.
Voiced and unvoiced sounds can also be used to create sound patterns in language. For example, in English, the plural morpheme -s is pronounced as /s/ or /z/ depending on whether the preceding sound is unvoiced or voiced. If the preceding sound is unvoiced, as in "cats," the morpheme is pronounced as /s/. If the preceding sound is voiced, as in "dogs," the morpheme is pronounced as /z/.
Overall, the distinction between voiced and unvoiced sounds is an important aspect of phonetics, as it can affect the meaning of words, the way in which they are pronounced, and the patterns of sound in language.