Does the word discharge sound more like /dɪstʃɑːʳdʒ/ or /dɪsdʒɑːʳdʒ/?
How about exchange or disproportion?
Do they sound more like /ɪkstʃeɪndʒ/ or /ɪksdʒeɪndʒ/?
/dɪsprəpɔːʳʃən/ or /dɪsbrəpɔːʳʃən/?
I know the word student which commonly sounds like /sdjuːdənt/.
and the dictionary says its IPA transcription is /stjuːdənt/.
you think they do because you're confusing the plosives in your native language with the plosives in English.
English has two bilabial plosives—voiced bilabial plosive /b/ and voiceless bilabial plosive /p/, two alveolar plosives—voiced /d/ and voiceless /t/ and two velar plosives—voiced /g/ and voiceless /k/
In English, they're distinguished through voicing; /p/, /t/ and /k/ are voiceless while /b/, /d/ and /g/ are their corresponding voiced counterparts.
They are phonemes—mental representation of sounds, but can be realised in more than one way. For instance, /t/ has many allophones (realisations):
All these are the different realisations of the same phoneme /t/.
The most common allophones of /t/, /p/ and /k/ are respectively [tʰ, t], [pʰ, p] and [kʰ, k].
In English, if you use them interchangeably, they won't change the meaning of the word. For example, the word pin is supposed to be pronounced [pʰɪn], but if you pronounced the p without aspiration (i.e. [pɪn]), it wouldn't change the meaning (as Spanish speakers usually do). That is to say, aspiration isn't phonemic in English.
Whereas in other languages like Chinese, aspiration is a distinctive feature for certain sounds (i.e. aspiration is phonemic).
In Pinyin:
By contrast,
In words beginning ⟨sp-⟩, ⟨st-⟩, and ⟨sk-⟩, English speakers use 'voiceless unaspirated plosives'. For instance, the p in pie is aspirated, but unaspirated in spy:
In Pinyin, ⟨sp-⟩, ⟨st-⟩, ⟨sk-⟩ would be represented by ⟨sb-⟩, ⟨sd-⟩, and ⟨sg-⟩, respectively. So you see there's a mismatch between English plosives and Chinese plosives.
That's why you hear sdudent for student, sgool for school and sby for spy.
Whereas in words beginning ⟨p-⟩, ⟨t-⟩ and ⟨k-⟩, English speakers use 'voiceless aspirated plosives'. Examples:
In Pinyin, ⟨p-⟩, ⟨t-⟩, ⟨k-⟩ would also be represented by ⟨p-⟩, ⟨t-⟩, and ⟨k-⟩, respectively. So you hear pie, time, kite correctly.
The same thing is going on with affricates (/t͡ʃ/ and /d͡ʒ/). Affricates in some dialects of English are aspirated, but it varies from speaker to speaker. And if you hear [st͡ʃ] as [sd͡ʒ], then there certainly is aspiration which is affected by the preceding [s] (the same way as [s] affects the aspiration of p, t and k).
Or if /t͡ʃ/ and /d͡ʒ/ are unaspirated, then they're only distinguished through voicing in English and voicing in Chinese is not phonemic so Chinese speakers confuse them easily.
Notes: