I am confused about this question for long time but no internet resource explains about this.
Ok, when we have a consonant followed by an vowel in a pronunciation then for sure we have to fully aspirate the sound of that consonant. For example, in has /hæz/, we will fully aspirate /z/. That is meaningful. No problem right.
Now, when we have 2 consonants standing next to each other and at the end of a pronunciation, then my question is:
Should we fully aspirate both of these 2 consonants?
For example, in books /bʊks/, should we fully aspirate /k/ and then fully aspirate /s/. So, to pronounce /bʊks/, we will make 3 sounds:
-fully aspirate /bʊ/
-fully aspirate /k/
-fully aspirate /s/
Note: fully aspirate means fully pronounce (a sound) with an exhalation of breath. For example, when you fully aspirate /k/ (see video here https://www.youtube.com/watch?v=RhS65K59ogA, the lady made the /k/ sound in the time of 0:24)
Or
Should we fully aspirate the last consonant only and the before consonant should be in the starting position and your tongue will make the sound of the last consonant from that starting position?
For example, in books /bʊks/, when we finish the sound /bʊk/ the back of the tongue will touch the soft palate and at that point of time we won't release the tongue to make the sound /k/ but release the tongue to the /s/ position to make the /s/ sound.
I believe that if we make the sound like that then it will be different from when people won't put their tongue at the /k/ position but after /bʊ/ they will make /s/ immediately and it will sound like /bʊs/
Ok, to make my question clearer, I recorded my voice so that you can imagine what I am asking about:
This voice shows the /bʊks/ with aspirate of both /k/ and /s/. See https://drive.google.com/file/d/0B9o9iLQ2SktLUHpmcnF2TFRCRTg/view?usp=sharing
This voice shows the /bʊks/ with aspirate of /s/ only. See https://drive.google.com/file/d/0B9o9iLQ2SktLQVNMc0ZZSUhVaXM/view?usp=sharing
I think this is a very interesting question!
Best Answer
After your edit and the clarification the comments to the question have brought about, it is now much clearer what it is you’re asking here.
The simple answer is no.
Generally speaking, plosives in English are mandatorily aspirated [pʰ tʰ kʰ] when they come at the start of a stressed syllable, or (usually) word-initially. In all other cases, they are usually non-aspirated [p t k], though they may sometimes optionally be aspirated for effect.
Aspiration here refers to a short period of time after the closure in the oral cavity that blocks the airflow is released, but before your vocal cords start vibrating to produce a voiced sound. During the aspiration phase, also known as the voice-onset time, there is airflow, but no voice; you’re essentially pronouncing a [h]. When a /k/ comes at the start of a stressed syllable, the voice-onset time in English tends to be somewhere around 80 ms. Even in unaspirated plosives, your vocal cords don’t start vibrating immediately: unaspirated /k/ normally has a voice-onset time of about 15–20 ms in English.
In the example you give, books, the /k/ comes in the syllable coda, and as such is not normally aspirated. If you really want to emphasise that you’re saying books and not boogs, then you can aspirate the /k/ and say [bʊkʰs], but that is not very common, so use it sparingly.
However, the sound that follows /k/ here is a voiceless fricative and therefore by definition entails a continuous unvoiced airflow, just like regular aspiration does. The only difference is that in /s/, the unvoiced airflow is restricted by the position of the tongue against the roof of the mouth, with only a narrow hole the air can pass through.
When your tongue transitions from [k] to [s], the back of the tongue has to ‘let go’ of the soft palate, while the blade of the tongue in front has to ‘catch’ the alveolar ridge. These two movements are naturally difficult to time exactly, and it is very common that the first takes place perhaps 40–50 ms before the second. During that period, you do likely have some aspiration of the /k/; but it is not really noticeable, because it is shorter than the ‘full’ aspiration we find in can [kʰan] (perhaps half as long), and it tends to blend in with the sibilant airflow of the following /s/.