[williw]

In standard Beijing Mandarin pronunciation? If you have a dialect then you might have stronger "sh" sound when trying to pronounce "si" "ci" "zi" "xi", so it's hard do differentiate between "si" and "shi", "ci" and "chi" or "zi" and "zhi". 四是四，十是十，十四是十四，四十是四十。

[csa]

I humbly suggest that Beijing Mandarin pronunciation is not “standard” putonghua — otherwise, mostly of these sounds would end with a retroflex /r/.

I forget the details now, but “standard” putonghua has two variants, and each variant revolves around Jiangsu province (something like north and south?). Anyway, Beijing people think that they speak the “standard”. People educated in linguistics know better.

[williw]

I beg to differ. Read here: "Its pronunciation is based on the Beijing dialect, its vocabulary on the Mandarin dialects, and its grammar is based on written vernacular Chinese."

https://en.wikipedia.org/wiki/Standard_Chinese