The term, however, is used to refer to two separate concepts: For example, voicing accounts for the difference between the pair of sounds associated with the English letters ⟨s⟩ and ⟨z⟩.
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 while [z] is pronounced but not with [s].
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.
[1] When used to classify speech sounds, voiced and unvoiced are merely labels used to group phones and phonemes together for the purposes of classification.
The International Phonetic Alphabet has distinct letters for many voiceless and voiced pairs of consonants (the obstruents), such as [p b], [t d], [k ɡ], [q ɢ].
The sequence of phones for nods might be transcribed as [nɒts] or [nɒdz], depending on the presence or strength of this devoicing.
What complicates the matter is that for English, consonant phonemes are classified as either voiced or voiceless even though it is not the primary distinctive feature between them.
Such processes allow English speakers to continue to perceive difference between voiced and voiceless consonants when the devoicing of the former would otherwise make them sound identical to the latter.
Voiceless phonemes are typically unaspirated, glottalized and the closure itself may not even be released, making it sometimes difficult to hear the difference between, for example, light and like.
However, auditory cues remain to distinguish between voiced and voiceless sounds, such as what has been described above, like the length of the preceding vowel.
However, they may be devoiced in certain positions, especially after aspirated consonants, as in coffee, tree, and play in which the voicing is delayed to the extent of missing the sonorant or vowel altogether.