rendering

"I have heard up to four announcements playing at once , rendering all of them unintelligible  in a hurricane of noise."

我對這句話大概的理解如下
"我曾經聽過四種廣播同時撥放,這讓廣播的內容像颶風的噪音一樣,完全聽不出來在講什麼"

這句話是否能寫成
"I have heard up to four announcements playing at once , that render all of them unintelligible  in a hurricane of noise."
???

如果可以那我的疑問是,以前我一直認為子句的主詞和主句一樣才能拿掉連接詞,然後把動詞改成動名詞(render =>rendering),可是如果像這句這樣 "render"的主詞因該不是前面的"I",那為何能寫成"rendering all of them xxxx"??