Most sources which I encountered say that English consonants [p], [t], [k] are aspirated before a vowel but not after [s], and become unaspirated after [s]. Canonical example: [p] is strongly aspirated in "pear", but unaspirated in "spear". My question is: what about the position of [p], [t], [k] before another consonant, notable before [r] or [l]? Examples: plane, pride, train, clue, crow etc. Are [p], [t], [k] in these cases aspirated or not?

  • Thanks for answers. For some reason, many native English speakers realize P in "please" with aspiration; at least, I found it at Speech accent archive: accent.gmu.edu/…. Maybe it is a dialectal feature, or it's a mistake in recording, or I understood it wrong.
    – Alexander
    Mar 19, 2017 at 11:56
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    I'll give you an answer shortly. The answer is "yes - but we don't call it aspiration". Mar 19, 2017 at 12:04
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    I reselected the answer. Thanks for a very detailed explanation and the provided link.
    – Alexander
    Mar 19, 2017 at 13:28
  • You're welcome. It was a very useful and interesting question!! :-) Mar 19, 2017 at 13:32
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    @MilesRout That's not entirely correct. Aspiration is a key feature for English speakers in deciding whether a preceding consonant is voiced or voiceless (or to be more technically correct lenis or fortis). Mar 20, 2017 at 13:40

4 Answers 4


When we make a voiced sound, for example a vowel sound, our vocal cords vibrate. This gives the sound pitch. We can make voiced sounds with a high pitch or a low pitch. For this reason, you can sing a tune using a [z] sound. You cannot do this, for example, with an unvoiced sound like [s]. We don't vibrate our vocal folds for an [s] sound, so it has no musical pitch. All vowel sounds are voiced, of course.

When the voiceless plosives [p, t] or [k] occur at the beginning of a stressed syllable in English, they have an effect on the following voiced sounds. In English there are rules about what types of sound can occur after these consonants when they occur at the beginning of a syllable (these are called phonotactic rules or phonotoactic constraints). English only allows the consonants /r, l, w, j/ or a vowel after a /p, t/ or /k/ at the start of a syllable.

Now, the phonemes /r, l, w, j/ and the vowel sounds are voiced. This means that they have pitch and that our vocal cords vibrate when we make them. However, after [p, t, k] at the beginning of a stressed syllable something strange happens. There is a delay before our vocal cords start vibrating. So, for example, in the word pool /pu:l/, there is a gap between our lips opening for the [p] and our vocal cords vibrating for the following [u]. This gap is called the Voice Onset Time. The Voice Onset Time in English is quite long in this situation. After we release our lips for the [p] in pool air starts rushing out of our mouths as it is pushed up from the lungs. During the gap between the [p] and our vocal folds starting to vibrate, we can hear this air rushing out of our mouths. It sounds like an [h]. In a word like pool where the sound after the plosive is a vowel sound, we call this [h]-like quality at the beginning of the vowel aspiration. Really what we are hearing is a devoiced vowel. Our mouths are already making the vowel shape but the vocal cords have not started vibrating yet.

Exactly the same thing happens when the sound after the [p, t] or [k] is one of the approximant sounds [r, l, w, j]. There is a gap after the release of the [p, t] or [k] before the vocal folds start vibrating. So in the word clean /kli:n/, for example, there is a gap after the [k] sound before the vocal folds start vibrating for the voiced [l]. During this gap our mouths are already making the necessary [l] shape but there is no vocal fold vibration. We will hear the air rushing out of the mouth from the lungs. It will have an [h]-like quality, but it will have an [l]-like quality too. In this situation we say that the [l] has become devoiced. However, we do not call the hissing noise that we hear aspiration when it occurs during a consonant sound like [r, l, w, j].

The Original Poster's question

When [p, t] or [k] occur at the beginning of a stressed syllable, they cause a delay in the voicing of the following sound. This delay is known as the voice onset time. During the delay we will hear a devoiced version of the following vowel or consonant. There will be a hissing noise as the air escapes from the lungs before the vocal cords start to vibrate. This happens regardless of whether the following sound is a vowel or a consonant such as [r, l, w, j]. When the following sound is a vowel we call this hissing noise aspiration but when the following sound is a consonant such as [r, l, w] or [j], we just say that the consonant has become devoiced.


You can hear a nice example of this type of devoicing on this page by Goeff Lindsey.

Transcription note

I have used the [r] symbol to represent the sound we make when we say an English /r/. This is to make the post easily readable. However, the standard English /r/ sound is technically not [r], but [ɹ].

  • To make a long hiss after [k] the speaker in the recordings isn't realistically forming the [r]. He is delaying the [r] rather than forming it in concert with the [k]. If the airway is tightly occluded in the back of the throat to form the [k] and if the occlusion persists during the buccal tensing required to produce the [r], or that tensing occurs at the start such that the [r] is produced in tandem with not sequential to the formation of the [k], then there is no outpuff of air between [k] and [r]: the outpuff of air occurs as the [kr] mouth formation is relaxed simultaneously.
    – TimR
    Mar 19, 2017 at 14:06
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    Possibly related—what's going on when the tr- at the start of a word sounds more like chr-? That is, if I pay close attention, words like tree and try are said almost like they begin with the starting sound as in cheese or child, except with an /r/ tucked in there, at least in my area (US Midwestern/Great Lakes). Is this a related phenomenon?
    – 1006a
    Mar 19, 2017 at 16:11
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    @1006a Good question. What's happening there is that when you make a /t/ you nomally make it with the blade of your tongue on your alveolar ridge. But an /r/ is made with the tongue tip behind the alveolar ridge. So when we get a sequence of /t/ and /r/, the /t/ is made further back on the ridge so that you can move smoothly from the /t/ to the /r/. (You can test this. Say "tie, tie, tie" and feel where you're making your /t/ in your mouth. Then say "try, try, try". Then "tie, try, tie, try". Mar 19, 2017 at 17:53
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    @1006a ... You should be able to feel that your tongue touches the top of your mouth further back for the "try" than for the "tie." Now, when you release the /t/ closure in "try" the tip of your tongue moves straight to the /r/ and there is not a lot of space for the air to escape cleanly as with a normal /t/. This means that instead of escaping cleanly the air is forced through a narow gap and becomes turbulent causing a strong hissing noise. This changes the /tr/ sequence into a new sound which we call a "post alveolar apico-affricate". It happens in most standard Englishes. Mar 19, 2017 at 17:57
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    @TRomano The /r/ articulation continues long after the /k/ is released. The /r/ is not "delayed" in any way (as is clear from the fact that, as your point out, the /r/ articulation is already in place before the /k/ is released. The reason we wouldn't want to say that the /r/ is "delayed" is that it may never be voiced at all. In other words the devoiced /r/ is the whole /r/ in many cases. Of course, if you were correct and the /r/ was delayed, then the "hissing" would of course be occurring between the first and second consonants. But as you point out, the /r/ isn't delayed :) Mar 19, 2017 at 19:41

A /p/, /t/ or /k/ is aspirated when it is the first consonant of a stressed syllable, whether it is followed by a vowel or by a semivowel or liquid consonant. The words plane, pride, train, clue, crow all start with aspirated stops.

As Araucaria's answer says, in a consonant cluster consisting of a syllable-initial voiceless stop phoneme + a consonant such as /l/, /r/, /j/ or /w/ the "aspiration" of the stop is realized largely as devoicing of the following consonant (I think it can be devoiced entirely, but perhaps more commonly it is only "partially devoiced" with a voiced second part before transitioning to the following vowel). This is not really a big difference phonetically from the situation before a vowel since aspiration before a vowel largely consists of partially devoicing the vowel.

It is of course good to remember that in English, "clusters" of consonants that fall within the same syllable tend to be very coarticulated; they are pronounced with one "breath" and not separated by any kind of pause or intermediate release. The aspirated release of the syllable-initial stop is more or less simultaneous with the pronunciation of the second consonant; you don't wait for the release before starting to pronounce the second consonant. (In fact, as TRomano and Araucaria mention in the comments below Araucaria's answer, the "second" consonant generally affects the pronunciation in subtle ways even before the release of the "first" consonant: for example in a cluster like /kj/ the /k/ will start out with a more fronted pronunciation (phonetically [k̟] or [c]) in anticipation of the phonologically later palatal glide phoneme /j/. So terms like "first" and "second" consonant make sense phonologically, but not so much phonetically.)

It's important to differentiate in this regard between consonant clusters that occur at the start of a syllable, such as pl-, kr-, tw-, and consonant clusters that occur between syllables, such as pt, kt. The syllable-initial /p/ in "apply" is almost always aspirated, but the syllable-final /p/ in "optician" almost never is. Instead, the release of the /p/ is "masked" by the transition to the following plosive /t/ (which does have an aspirated release, since it is at the start of a stressed syllable).

You can find some information about allophonic aspiration in English on John Wells's phonetic blog; see VOT is that?, VOT is more.

  • Thanks for a good answer. Unfortunately, I am out of votes today. I'll vote up tomorrow, if you permit.
    – Alexander
    Mar 19, 2017 at 18:37

There is no outpuff of air between [p] and [l] or between [k] and [l], or between [p],[k], or [t] and [r].

P.S. Because there is no "between" there to speak of. The mouth is in position to produce both sounds from the outset. The mouth (tongue, cheeks, lips) is in position to produce [kr], for example. As the cheeks are relaxing to resolve the [r] and transition to the vowel, the voicing occurs.

  • Sorry T, but that's not correct. There is a puff of air between the end of the plosive and the start of the voicing for the following consonant. When the next sound is a consonant instead of calling this hissing aspiration we just say the the following consonant has become devoiced. However, it is exactly the same phenomenon (aspiration is just a devoicing of the following vowel). Mar 19, 2017 at 13:30
  • What "hiss" are you referring to with [p] and [k]? And I said there was no outpuff between the two consonants.
    – TimR
    Mar 19, 2017 at 13:42

The combinations sp, st, pl, pr, cl, cr, tr etc. are digraphs - meaning they are two letters which make a single sound - they are pronounced together, with no aspiration between.

  • It's tricky, though. I don't know much about linguistics, but when I listen to myself I hear a definite separation between the "s" and the "t' in "steak", where the s is (necessarily) aspirated but the t is not. However, as you say, the "tr" in "train" is pronounced as one, aspirated, sound.
    – Andrew
    Mar 19, 2017 at 11:49
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    There is no aspiration between e.g. the /k/ and /l/ of "climb," but there is aspiration during the release of the first consonant (which is simultaneous with part of the duration of the second consonant).
    – sumelic
    Mar 19, 2017 at 18:41
  • @Andrew That's because in order to pronounce /t/ you have to stop the flow of air, that's why it's called a stop.
    – user51356
    Mar 20, 2017 at 4:23

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