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I am a Chinese student beginning to learn English. I am curious to know why the word student is pronounced with the sound of d instead of t. Likewise, why is the sound of b used instead of p when people say suspend?

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    Welcome to English Language and Usage! Also consider using English Language Learners. – M. K. Hunter Nov 24 '14 at 12:33
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    Hey Zezhong. The short answer is because it's easier to pronounce that way, especially when speaking quickly. Try it: in a slow and exaggerated way, articulate "suspend" with the "p" sound, and pay particular attention to the effort of transitioning from the s to the p. Now do it again with the "b" sound, and compare the transition s-b to the earlier s-p* transition. Now do it a few more times, speaking faster each time. The broader, big picture answer, is that English words are very often not pronounced as they're spelled (or vice-versa), and natives don't expect them to be. – Dan Bron Nov 24 '14 at 12:39
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    Instead of leaving a "thank you" comment, we would prefer that you upvote answers that you found helpful. Upvotes confer reputation points upon users, and points are the most public form of thanks possible, since they are the currency that makes this community work. – 200_success Nov 24 '14 at 19:51
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    @HotLicks: You’re making it sound like you think all European languages have more or less the same phonemes, and all East Asian languages have more or less the same phonemes. They don’t; this is not the case even for European languages, which are mostly related to each other, but the major East Asian languages are even completely unrelated. – Timwi Nov 24 '14 at 21:19
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    @Timwi - Sweeping generalizations, granted, but I think they apply. What I discussed is the basis for the "Charlie Chan" accents in old movies, eg. – Hot Licks Nov 24 '14 at 21:23
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The 't' in student is not pronounced like a 'd'. You just think it is because there is a mismatch between the consonants in the Chinese language and the consonants in English.

Pinyin uses the letter 'd' for an unaspirated voiceless alveolar stop (represented /t/ in IPA), and the letter 't' for an aspirated voiceless alveolar stop (represented /tʰ/ in IPA). English uses the letter 'd' for an unaspirated voiced alveolar stop (represented /d/ in IPA), and the letter 't' for a voiceless alveolar stop, which is either aspirated (/tʰ/) or unaspirated (/t/) depending on its position in the word. Since there are no voiced stops in Chinese, you're not used to distinguishing between stops depending on whether they are voiced and unvoiced, so you don't hear the difference between a /t/ and a /d/, while /tʰ/ sounds different from both of them.

In words beginning 'st', 'sp', and 'sk', I believe all dialects of English use the unaspirated unvoiced stops ('sd', 'sb', and 'sg' in Pinyin), and in words beginning 't', 'p', 'k', they use the aspirated unvoiced stops ('t', 'p', and 'k' in Pinyin). Thus, at the beginning of words, the consonants 't', 'p', 'k' are distinguished from 'd', 'b', 'g' both by being aspirated and by being unvoiced. In the middle of words, things are more complicated; here, the consonants 'd', 'b', 'g' are distinguished from 't', 'p', and 'k' by being voiced.

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    This answer is spot on, and very thorough and to the point. I’m impressed! – Timwi Nov 24 '14 at 21:20
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    Something that might add to this already very good answer would be to explicitly mention that aspirating a plosive after an /s/ in English automatically leads English speakers to assume that the /s/ and the plosive belong to different morphemes/words. In other words, in BrE, [əstuːɫ] (unaspirated) would be heard as a stool, while [əstʰuːɫ] (aspirated) would be heard as as tool. If the plosive is actually voiced, the /s/ becomes voiced as well, so the equivalent voiced version, as Doole would be [əzduːɫ]. – Janus Bahs Jacquet Nov 25 '14 at 11:50
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    As a minor extension, because English does not distinguish aspirated or unaspirated stops, you will hear native speakers use them unpredictably and even inconsistently from word to word. There are general rules of thumb (Peter listed them), but they are not perfect. We have the same problem when trying to listen to a native Mandarin speaker use words like dao/tao and chi/qi. When we try to imitate your pronunciation, we murder it because we literally do not hear the distinction between aspirated stops and non-aspirated when you use them. – Cort Ammon Nov 26 '14 at 1:23
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The "d" in student is called a 'voiced dental'. It is produced with the tongue pressed up against the roof of the mouth behind the two front teeth. But there is also a sound produced in the vocal cords at the same time as the air is forced out; thus, it is 'voiced'. The 't' at the end of the word is a 'voiceless dental'. The tongue position is the same but there's no vibration of the vocal cords.

Compare dip, tip, dare, tare, seed, seat

This site would be helpful for you: http://ell.stackexchange.com

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    I thought OP was asking about the first t in the word. I.e., why (to OP) is seems that student is pronounced like sdudent. – Joshua Taylor Nov 24 '14 at 22:39
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    You may very well be right. But [st] isn't pronounced with a voiced dental. – TRomano Nov 24 '14 at 22:46
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    Right, but that distinction may not be as clear to a Chinese student new to the language. Peter Shor's answer touches a bit more on that. – Joshua Taylor Nov 24 '14 at 22:47
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    Note that the asker doesn’t talk about voicedness at all (probably because he is unaware of the terminology and the phonetic descriptions involved): he just says d and t, which are very relative terms that depend on what language we’re talking about. – Janus Bahs Jacquet Nov 25 '14 at 14:31
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To explain this, I need to use some technical terminology. Here it is:

  • Voiced – pronounced with the vocal folds vibrating. [s] is unvoiced, while [z] is voiced.
  • Aspirated – pronounced with a following puff of air. [tʰ] as in English ‘tea’ or Mandarin 他 is aspirated.
  • Square brackets – [tʰ] – represent sounds as we make and hear them. Slashes – /d/ – represent phonemes, which are the meaningful units that we translate sounds into without thinking. In English, [t] and [tʰ] can be two ways of pronouncing a single phoneme, /t/.

In Mandarin, the distinction between 搭 and 他 is one of aspiration. The Pinyin spelling, though useful for other reasons, is misleading. In IPA, these are written [ta] and [tʰa].

In English, we may or may not voice ‘d’ at the beginning of a word. So ‘die’ may be either [daɪ] or [taɪ]. We hear [taɪ] as /daɪ/ because we don’t make a distinction. If it were ‘tie’, we would hear [tʰaɪ]. At the beginning of a word, or before a stressed syllable in English, the primary distinction between /t/ and /d/ is aspiration, not voicing. This is the same distinction that Chinese makes.

However, after the letter ‘s’, ‘t’ is not aspirated. The word ‘sty’ is pronounced [staɪ], not [stʰaɪ]. Thus, to the ears of a Mandarin speaker, it sounds like a /b/. It all has to do with the way that our ears translate the sounds into phonemes.

The same phenomena that apply to t/d apply to k/g and p/b.

Furthermore, before unstressed syllables, aspiration also doesn’t happen. In this case, /b g d/ must be truly voiced to make them distinct from the unaspirated versions of /p t k/. So ‘happy’ is [hæpi], while ‘cabby’ is [kæbi]. Notice that the /p/ in ‘happy’ is the same sound as the unaspirated /b/ in Mandarin 笔 . But in English, it contrasts with /b/ and matches with /p/. It is the unaspirated form of /p/.

One final thing: in American English, /t/ between a vowel is pronounced exactly like /d/. Both become a flap, [ɾ], which is the sound of ‘r’ in Spanish.

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    Thanks for your basic explanation of the concepts. Peter's answer jumps right in with an "unaspirated voiceless alveolar stop," which lost me right away. After reading your answer as well I'm starting to make much more sense of these ideas. – fooot Nov 26 '14 at 16:56
  • @fooot Thanks. Let me know if I can explain more – there's a lot going on, and none of it is self-evident! – Micah Walter Nov 26 '14 at 17:23
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The initial s and t in student are unvoiced, but the '-ud-' is voiced. Because many native English speakers are a little sloppy in their diction, the vocal chords may start up a fraction of a second before the alveolar plosive and so the t sounds somewhat like d. "sdudent".

This effect is less commonly heard in British English than in American English due to the difference in the vowel sound.

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    The first /t/ is voiceless; the difference is that it's unaspirated. – echristopherson Nov 25 '14 at 4:42

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