Chinese usually use a similar onomatopoeic word “嘘(xū)". 嘘 also has another pronunciation shī which is closer to "shhhh". Both of them mean "be quiet", whereas the later sounds more serious. BTW, could you please help me check these↑↑ sentences? THX ：)

嘘 is a polyphone word，if you want to express someone to be quiet, 嘘should pronunce as (shī), this is same as shhhhh in english

嘘 shī

Th sound that chinese mums make to help their babies pee is "shü". If you know how to pronounce the german umlaut "ü", then you know what it sounds like.:>

噓 在 台灣只有唯一的 xu1 但擬聲時 該是 "shhhh". 尤其在拉長聲音之後 更能分辨 因為長時間的圓唇音xu1會很費氣力 故言 ditto