Why does /stress/ always prounciate /sdress/?

[sdire]

I have a big question about prounciation. I always see 'study' in dictionary prounicated as /studi/, but we acctually prounicate like /sdudi/. What's the reason? And if it is correct, when we prounicate 'stress' as /sdress/?

[5jj]

I have a big question about prounciation. I always see the pronunciation of 'study' in a dictionary prounicated given as /studi/, but we acctually prounicate pronounce it as like /sdudi/.
We don't.

Even if we did, the initial /s/ would cause the /d/ to be devoiced, resulting in something that sounded more like /st/ than /sd/

[sdire]

Even if we did, the initial /s/ would cause the /d/ to be devoiced, resulting in something that sounded more like /st/ than /sd/

Thank you very much. If I'm not misunderesting, it is /tr/ not /dr/, even sounded like /dr/? Like /stres/ sometimes sounds /sdres/? How about /sta:/ sounds like /sda:/? Is it the same reason?

[bhaisahab]

Thank you very much. If I'm not misunderesting, it is /tr/ not /dr/, even sounded like /dr/? Like /stres/ sometimes sounds /sdres/? How about /sta:/ sounds like /sda:/? Is it the same reason?

As fivejedjon has said, "st" does not sound like "sd".