在我国英语教学中，讲到所谓「s 后清辅音浊化」时，大概分以下三种：
1. 通常意义的重音音节。比如：stop、spring 这些是要所谓「浊化」的。
2. 非重读音节是否需要所谓「浊化」？下面这些单词应该怎么读：basketball、landscape。
3. 是分开的词或者词头的应该怎么读？比如 ice cream、ice tea、discover。
作者：栗子
范老师口头禅：/s/后的清辅音需要浊化（不送气），除非/s/属于独立的前缀（如discontinue)。
这是一个很复杂的语言学问题，很多英语母语者也没想过。我之所以知道怎么解释这个问题，是因为有不止一个中国学生问我这个问题以后我查过资料。
我建议你在学英语的时候不要过于纠结这个[浊化]现象，如果你把[s], [t], [ɒ] 和 [p]都发对，你在说“stop”的时候想都不用想就能发得和母语者一样。
下面的解释不是用来提升你的发音水平的，如果你真的希望知道究竟再看下去吧（我做了一个视频来帮助你理解，请上面↑）
事实上，这个问题本身是不准确的。简单地说，[t] 这个音 在 “top” 和 “stop”中的区别不是清辅音和浊辅音的区别，而是送气与不送气[翻译君也不知道怎么解释这个，作为一只英专生，我学的是ptk是爆破音（也是清辅音） 而bdg是浊辅音]的区别，这也是为什么stop用国际音标标出来是[stɒp]而不是 [sdɒp]。
以下是造成这个现象的两个主要原因：
1.节省能量
送气音在英语中非常重要，所谓送气音就是在发辅音的时候把气猛得送出来，尤其是[p,t,k]的音[这应该就是爆破音了 雾]
你要用很多空气和能量来发好一个送气音。但是不幸的是，[s]这个音也要很多气来发。因此，当“p”, “t”, 和 “k” 在 “s”后时，由于缺少足够的气来发这个送气音的同时又得留一些气来发后面的对于一个词的发音准确度更重要得多的元音。
因此，在“s”之后省略[p], [t], 和 [k]音对于大家来说都要简单得多。这也导致了它们听起来像[b], [d], 和[g]。这个现象的原因与语言心理学有关而与我们现在说的问题无关。如果你对此很感兴趣，想了解更多的话就请自己去查资料吧。
2. “它”并不必要
人们只需对那些在他们的语言中包含不同信息的声音敏感就行了。英语母语者省略送气音，即便这样使一个清辅音听起来像一个浊辅音也没关系，因为这不会影响发音的准确性。在英语中找一个词带着“sb”“sd”“sg”是不可能的，所以也没必要故意去发这个送气音来区分[stɒp] 和 [sdɒp]之类的词。
总而言之，这一现象的原因有两个：
- 在“s”之后把“p”, “t” 和“k”发成爆破音太费劲了
- 省略这个送这个气也并不会使一个词听起来像另外的词。
This is a very complex linguistic question that most native English speakers have never thought about. I know how to explain this, only because I did research when more than one of my Chinese students asked me this.
I would recommend not paying too much attention to this phenomenon when learning English. If you pronounce [s], [t], [ɒ] and [p] correctly, your “stop” will sound exactly the same as a native speaker would say it without thinking about how to make the [t] sound.
The following explanation is not to help you improve your pronunciation; please continue only if you really want to know why. (I also made a video to help you understand. Please see above.)
Actually, the question itself is inaccurate. Simply, the difference between the [t] sound in “top” and “stop” is NOT voiceless and voiced, but rather aspirated and non-aspirated. This explains why stop is transcribed in IPA as [stɒp], not [sdɒp].
There are two main reasons for this phenomenon:
1. To save energy
Aspiration is very important in English. Aspiration is the strong burst of air expelled when pronouncing consonants, especially [p, t, k].
To make a good aspiration, you need to use a lot of air and energy. Unfortunately, the [s] sound also requires a lot of air. Therefore, when “p”, “t”, or “k” comes after “s”, there is less air to make the aspiration, and some air must be saved to pronounce the following vowel(s), which are much more important for accurate pronunciation.
Therefore, it is much easier for people to omit the aspiration of [p], [t], and [k], when they follow “s”. This can cause them sound like [b], [d], and [g]. The reason for this is related to psycholinguistics and not relevant to the question at hand. Please do your own research if you are interested in knowing more about this.
2. It is unnecessary
People need to be sensitive to different sounds only when those sounds deliver different messages in their languages. Native English speakers omit the aspiration, even if it makes a voiceless consonant sounds like a voiced consonant is because it does not influence the accuracy of the pronunciation. It is impossible to find an English word with “sb”, “sd”, or “sg” in it so it is unnecessary to have the aspiration to make it easier to distinguish [stɒp] and [sdɒp], for example.
So, in summary, the reasons for this phenomenon are:
1. It takes too much energy to make an aspirated “p”, “t” or “k”, after “s”.
2. Omitting the aspiration doesn’t make the word sound like another one.
I hope this answer is helpful.