I've been having some trouble understanding how is it that what differentiates, for example, /p/ from /b/, is the vibration of the vocal chords, present in /b/, but not in /p/. From what I have read and have been told, /b/ can't be produced without the vibration of the vocal chords. But, for my untrained ear and amateur testing, it seems it is possible to produce both /b/ and /p/ while whispering (therefore, voicelessly).

So I'm really confused. I understand how /s/ has to be voiceless and /z/ has to be voiced, but not in cases like /t/ versus /d/. I've heard the opinion that the difference is clearer if the vocal chords vibrate, even though this is not the primary distinctive feature between them. So is it just a conventional practice for easier reference or does my judgement trick me?

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    See the related question on Whispered Voiced Consonants. Commented Mar 18, 2013 at 14:49
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    This is really the difference between (say) the phone [b], which is always voiced, and the English phoneme /b/, which is often realized as voiced [b], but which also has voiceless allophones (as do all consonants when whispered). This is essentially what phonemes were invented for, and why one must distinguish phonetic voicing from phonological voicing.
    – jlawler
    Commented Mar 18, 2013 at 17:47
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    In English there is another feature besides voicing which distinguishes /p/ and /b/. /p/ is aspirated while /b/ is not. Other languages have only the aspiration difference or a three-way difference between voiced, unaspirated, and aspirated. Stop consonants which are both voiced and aspirated don't really occur as far as I am aware. Commented Mar 19, 2013 at 3:02
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    @hippietrail, it's true that /p/ is sometimes realized as [pʰ] in English, but this metric is no more reliable than phonetic voicing as a distinguishing characteristic in all environments. For example, /p/ tends to be realized without any aspiration following it when it occurs in a syllable onset after /s/ (as in spot). It is also unaspirated (and often even unreleased) when occurring before another consonant (as in apt). Commented Mar 19, 2013 at 13:53
  • "For example, /p/ tends to be realized without any aspiration following it when it occurs in a syllable onset after /s/ (as in spot)" I always find that argument to be insufficient and I am wondering why people constantly bring it up. There is no opposition in the onset after /s/, so it could be either /p/ or /b/ there. Maybe there is convincing research that it cannot be /b/. Either way what I've read points to [voicing] having very little importance and that it is [aspiration] and the duration of the preceding vowel and the consonant itself that make the distinction between English /p : b/. Commented Dec 14, 2018 at 8:03

2 Answers 2


Before attempting to address this question, we need to be clear on what is meant by voiced. The concepts of phonological voicing and phonetic voicing are often conflated, which leads to many misunderstandings among students of linguistics. As I mentioned in my comment above, you might want to read my answer to a related question about Whispered Voiced Consonants.

When we talk about /b/, we are referring to a phoneme, and [+voice] is a phonological feature that it bears. This feature can be thought of as a mnemonic label that is derived from the fact that, in some environments, this phoneme can be distinguished from the phoneme /p/ by the presence of phonetic voicing during the realization of the former but not during the realization of the latter. One common environment where this is true in English is in the middle of a word between vowels (e.g. rebel vs. repel). You can check this by recording a native speaker saying these words and looking in the spectrograms for a voice bar during the stop closure in one case but not the other.

However, there are many environments in which /b/ is not realized with voicing during the closure, or in which it is only partly voiced. For example, for many speakers, at the beginning of an utterance, both /p/ and /b/ are realized without any voicing during the closure. It turns out that what is more relevant in distinguishing these phonemes in utterance-initial position is their voice onset time. Phonetic voicing starts right away after the closure of the /b/ but there is a delay in phonetic voicing in the case of the /p/ (there is aspiration noise in place of the phonetic voicing during this period). If we were to assign a narrow phonetic transcription to these sounds, we might actually consider this realization of /b/ to be [p] and this realization of /p/ to be [pʰ]. So, a stickler might say that the phone [b] must be produced with vibrating vocal folds, but the phoneme /b/ certainly can be realized without vocal fold vibration during the closure.

Even for /z/ and /s/, the distinction does not always lie in phonetic voicing. If you record a native speaker saying Say 'course' for me and Say 'cores' for me, where the target word ends in /s/ in the first case but /z/ in the second case, chances are you won't actually see much of a voice bar in the realization of the /z/. Instead, the more salient difference will be in the duration of the vocalic stretch before the fricative, and in the duration of the fricative itself. You may also see that the phonetic voicing from the vowel turns off a bit earlier before the [s] than it does before the [z].

So /b/, /d/, and /z/ can be distinguished from /p/, /t/, and /s/, respectively by the distinctive feature [+/-voiced] (although some prefer the use of lenis and fortis, as @Aspinea mentioned). But distinctive features are a way of categorizing the phonological behavior of segments, and while their names have been derived from the articulatory and acoustic characteristics of the phonemes to which they are assigned, they should not be considered literal phonetic descriptors.

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    Absolutely right on.
    – jlawler
    Commented Mar 18, 2013 at 17:48
  • I think this takes care of all of my confusion on the matter. Thanks!
    – Pedro Y.
    Commented Apr 1, 2013 at 16:00

From what I remember form a phonology class I took in unversity, the voicing of consonants is something that comes with fortis-lenis distinction at least in German and English.

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    There's lots of other independent features in various languages, like aspiration, fortis/lenis, intervocalic tapping, etc, that can allow us to tell "pat" from "bat" when they're whispered. It loses some information, but not all; that's why there's so much redundancy in language -- if we pick up on enough cues we don't need the others, and there's all kinds of cues, more than we need.
    – jlawler
    Commented Mar 18, 2013 at 17:51

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